hull structure and arrangement for the classification of cargo ships

Hull Structure and Arrangement for the Classification of

Cargo Ships less than 65 m and Non Cargo Ships less than 90 m

July 2014

Rule Note NR 600 DT R00 E

Marine & Offshore Division 92571 Neuilly sur Seine Cedex – France

Tel: + 33 (0)1 55 24 70 00 – Fax: + 33 (0)1 55 24 70 25 Marine website: http://www.veristar.com Email: [email protected]

2014 Bureau Veritas - All rights reserved

ARTICLE 1

1.1. - BUREAU VERITAS is a Society the purpose of whose Marine & Offshore Division (the "Society") isthe classification (" Classification ") of any ship or vessel or offshore unit or structure of any type or part ofit or system therein collectively hereinafter referred to as a "Unit" whether linked to shore, river bed or seabed or not, whether operated or located at sea or in inland waters or partly on land, including submarines,hovercrafts, drilling rigs, offshore installations of any type and of any purpose, their related and ancillaryequipment, subsea or not, such as well head and pipelines, mooring legs and mooring points or otherwiseas decided by the Society.The Society:

• "prepares and publishes Rules for classification, Guidance Notes and other documents (" Rules ");

• "issues Certificates, Attestations and Reports following its interventions (" Certificates ");• "publishes Registers.

1.2. - The Society also participates in the application of National and International Regulations or Stand-ards, in particular by delegation from different Governments. Those activities are hereafter collectively re-ferred to as " Certification ".1.3. - The Society can also provide services related to Classification and Certification such as ship andcompany safety management certification; ship and port security certification, training activities; all activi-ties and duties incidental thereto such as documentation on any supporting means, software, instrumen-tation, measurements, tests and trials on board.

1.4. - The interventions mentioned in 1.1., 1.2. and 1.3. are referred to as " Services ". The party and/or itsrepresentative requesting the services is hereinafter referred to as the " Client ". The Services are pre-pared and carried out on the assumption that the Clients are aware of the International Maritimeand/or Offshore Industry (the "Industry") practices.

1.5. - The Society is neither and may not be considered as an Underwriter, Broker in ship's sale or char-tering, Expert in Unit's valuation, Consulting Engineer, Controller, Naval Architect, Manufacturer, Ship-builder, Repair yard, Charterer or Shipowner who are not relieved of any of their expressed or impliedobligations by the interventions of the Society.ARTICLE 2

2.1. - Classification is the appraisement given by the Society for its Client, at a certain date, following sur-veys by its Surveyors along the lines specified in Articles 3 and 4 hereafter on the level of compliance ofa Unit to its Rules or part of them. This appraisement is represented by a class entered on the Certificatesand periodically transcribed in the Society's Register.

2.2. - Certification is carried out by the Society along the same lines as set out in Articles 3 and 4 hereafterand with reference to the applicable National and International Regulations or Standards.

2.3. - It is incumbent upon the Client to maintain the condition of the Unit after surveys, to presentthe Unit for surveys and to inform the Society without delay of circumstances which may affect thegiven appraisement or cause to modify its scope.2.4. - The Client is to give to the Society all access and information necessary for the safe and efficientperformance of the requested Services. The Client is the sole responsible for the conditions of presenta-tion of the Unit for tests, trials and surveys and the conditions under which tests and trials are carried out.

ARTICLE 33.1. - The Rules, procedures and instructions of the Society take into account at the date of theirpreparation the state of currently available and proven technical knowledge of the Industry. Theyare a collection of minimum requirements but not a standard or a code of construction neither aguide for maintenance, a safety handbook or a guide of professional practices, all of which areassumed to be known in detail and carefully followed at all times by the Client.Committees consisting of personalities from the Industry contribute to the development of those docu-ments.3.2. - The Society only is qualified to apply its Rules and to interpret them. Any reference to themhas no effect unless it involves the Society's intervention.3.3. - The Services of the Society are carried out by professional Surveyors according to the applicableRules and to the Code of Ethics of the Society. Surveyors have authority to decide locally on matters re-lated to classification and certification of the Units, unless the Rules provide otherwise.

3.4. - The operations of the Society in providing its Services are exclusively conducted by way of ran-dom inspections and do not in any circumstances involve monitoring or exhaustive verification.

ARTICLE 44.1. - The Society, acting by reference to its Rules:

• "reviews the construction arrangements of the Units as shown on the documents presented by the Cli-ent;

• "conducts surveys at the place of their construction;

• "classes Units and enters their class in its Register;• "surveys periodically the Units in service to note that the requirements for the maintenance of class are

met. The Client is to inform the Society without delay of circumstances which may cause the date or theextent of the surveys to be changed.ARTICLE 5

5.1. - The Society acts as a provider of services. This cannot be construed as an obligation bearingon the Society to obtain a result or as a warranty.

5.2. - The certificates issued by the Society pursuant to 5.1. here above are a statement on the levelof compliance of the Unit to its Rules or to the documents of reference for the Services provided for.

In particular, the Society does not engage in any work relating to the design, building, productionor repair checks, neither in the operation of the Units or in their trade, neither in any advisory serv-ices, and cannot be held liable on those accounts. Its certificates cannot be construed as an im-plied or express warranty of safety, fitness for the purpose, seaworthiness of the Unit or of its valuefor sale, insurance or chartering.

5.3. - The Society does not declare the acceptance or commissioning of a Unit, nor of its construc-tion in conformity with its design, that being the exclusive responsibility of its owner or builder.

5.4. - The Services of the Society cannot create any obligation bearing on the Society or constitute anywarranty of proper operation, beyond any representation set forth in the Rules, of any Unit, equipment ormachinery, computer software of any sort or other comparable concepts that has been subject to any sur-vey by the Society.

ARTICLE 6

6.1. - The Society accepts no responsibility for the use of information related to its Services which was notprovided for the purpose by the Society or with its assistance.

6.2. - If the Services of the Society or their omission cause to the Client a damage which is provedto be the direct and reasonably foreseeable consequence of an error or omission of the Society,its liability towards the Client is limited to ten times the amount of fee paid for the Service havingcaused the damage, provided however that this limit shall be subject to a minimum of eight thou-sand (8,000) Euro, and to a maximum which is the greater of eight hundred thousand (800,000)Euro and one and a half times the above mentioned fee. These limits apply regardless of fault in-cluding breach of contract, breach of warranty, tort, strict liability, breach of statute, etc.The Society bears no liability for indirect or consequential loss whether arising naturally or not asa consequence of the Services or their omission such as loss of revenue, loss of profit, loss of pro-duction, loss relative to other contracts and indemnities for termination of other agreements.

6.3. - All claims are to be presented to the Society in writing within three months of the date when the Serv-ices were supplied or (if later) the date when the events which are relied on of were first known to the Client,and any claim which is not so presented shall be deemed waived and absolutely barred. Time is to be in-terrupted thereafter with the same periodicity. ARTICLE 7

7.1. - Requests for Services are to be in writing.

7.2. - Either the Client or the Society can terminate as of right the requested Services after givingthe other party thirty days' written notice, for convenience, and without prejudice to the provisionsin Article 8 hereunder.

7.3. - The class granted to the concerned Units and the previously issued certificates remain valid until thedate of effect of the notice issued according to 7.2. here above subject to compliance with 2.3. here aboveand Article 8 hereunder.7.4. - The contract for classification and/or certification of a Unit cannot be transferred neither assigned.

ARTICLE 8

8.1. - The Services of the Society, whether completed or not, involve, for the part carried out, the paymentof fee upon receipt of the invoice and the reimbursement of the expenses incurred.

8.2. - Overdue amounts are increased as of right by interest in accordance with the applicable leg-islation.

8.3. - The class of a Unit may be suspended in the event of non-payment of fee after a first unfruitfulnotification to pay.

ARTICLE 9

9.1. - The documents and data provided to or prepared by the Society for its Services, and the informationavailable to the Society, are treated as confidential. However:

• "Clients have access to the data they have provided to the Society and, during the period of classifica-tion of the Unit for them, to the classification file consisting of survey reports and certificates which have been prepared at any time by the Society for the classification of the Unit ;

• "copy of the documents made available for the classification of the Unit and of available survey reports can be handed over to another Classification Society, where appropriate, in case of the Unit's transfer of class;

• "the data relative to the evolution of the Register, to the class suspension and to the survey status of the Units, as well as general technical information related to hull and equipment damages, may be passed on to IACS (International Association of Classification Societies) according to the association working rules;

• "the certificates, documents and information relative to the Units classed with the Society may be reviewed during certificating bodies audits and are disclosed upon order of the concerned governmen-tal or inter-governmental authorities or of a Court having jurisdiction.

The documents and data are subject to a file management plan.

ARTICLE 10

10.1. - Any delay or shortcoming in the performance of its Services by the Society arising from an eventnot reasonably foreseeable by or beyond the control of the Society shall be deemed not to be a breach ofcontract.

ARTICLE 11

11.1. - In case of diverging opinions during surveys between the Client and the Society's surveyor, the So-ciety may designate another of its surveyors at the request of the Client.

11.2. - Disagreements of a technical nature between the Client and the Society can be submitted by theSociety to the advice of its Marine Advisory Committee.

ARTICLE 1212.1. - Disputes over the Services carried out by delegation of Governments are assessed within theframework of the applicable agreements with the States, international Conventions and national rules.12.2. - Disputes arising out of the payment of the Society's invoices by the Client are submitted to the Courtof Nanterre, France, or to another Court as deemed fit by the Society.12.3. - Other disputes over the present General Conditions or over the Services of the Society areexclusively submitted to arbitration, by three arbitrators, in London according to the ArbitrationAct 1996 or any statutory modification or re-enactment thereof. The contract between the Societyand the Client shall be governed by English law.

ARTICLE 13

13.1. - These General Conditions constitute the sole contractual obligations binding together theSociety and the Client, to the exclusion of all other representation, statements, terms, conditionswhether express or implied. They may be varied in writing by mutual agreement. They are not var-ied by any purchase order or other document of the Client serving similar purpose.13.2. - The invalidity of one or more stipulations of the present General Conditions does not affect the va-lidity of the remaining provisions. 13.3. - The definitions herein take precedence over any definitions serving the same purpose which mayappear in other documents issued by the Society.

BV Mod. Ad. ME 545 L - 7 January 2013

MARINE & OFFSHORE DIVISIONGENERAL CONDITIONS

RULE NOTE NR 600

NR 600Hull Structure and Arrangement

for the Classification ofCargo Ships less than 65 m andNon Cargo Ships less than 90 m

Chapters 1 2 3 4 5 6

Chapter 1 General

Chapter 2 Structure Design Principles, General Arrangement and Scantling Criteria

Chapter 3 Design Loads

Chapter 4 Hull Scantling

Chapter 5 Other Structure

Chapter 6 Construction and Testing

July 2014

Unless otherwise specified, these rules apply to ships for which contracts aresigned after July 1st, 2014. The Society may refer to the contents hereof beforeJuly 1st, 2014, as and when deemed necessary or appropriate.

2 Bureau Veritas July 2014

CHAPTER 1GENERAL

Section 1 General

1 General 23

1.1 Wording1.2 Classification

2 Application criteria 24

2.1 Type of ship covered by the present Rules2.2 Ship types not covered by the present Rules2.3 Particular cases

3 Navigation coefficients 24

3.1 Navigation notation3.2 Sea going launch and launch

4 Definitions 24

4.1 Length4.2 Breadth4.3 Depth4.4 Moulded draught4.5 Total block coefficient4.6 Chine and bottom4.7 Lightweight4.8 Deadweight4.9 Freeboard deck4.10 Bulkhead deck4.11 Superstructure4.12 Platform of multihull

5 Reference co-ordinate system 26

5.1 General

6 Stability 26

6.1 General

7 Documentation to be submitted 27

7.1 Documentation to be submitted

Section 2 Materials

1 General 30

1.1 Application

2 Steels for hull structure 30

2.1 General

3 Aluminium alloys for hull structure 31

3.1 Characteristics and testing

July 2014 Bureau Veritas 3

4 Composite materials and plywood for hull structure 31

4.1 Characteristics and testing4.2 Application

Section 3 Scantling Principles

1 Main scantling principles 32

1.1 General1.2 Type of ships1.3 Corrosion addition1.4 Rounding off

2 Hull analysis approach 33

2.1 Hull girder and local strength2.2 Plating scantling approach


CHAPTER 2STRUCTURE DESIGN PRINCIPLES, GENERAL ARRANGEMENT AND SCANTLING CRITERIA

Section 1 Structure Design Principles

1 General 37

1.1 Application

2 Structural continuity of hull girder 37

2.1 General principles for longitudinal hull girder2.2 General principles for platform of multihull2.3 Insert plates and doublers2.4 Connections between steel and aluminium

3 Bottom structure arrangement 38

3.1 General arrangement3.2 Longitudinal framing arrangement of single bottom3.3 Transverse framing arrangement of single bottom3.4 Double bottom arrangement3.5 Arrangement, scantlings and connections of bilge keels

4 Side structure arrangement 39

4.1 General4.2 Stiffener arrangement4.3 Openings in the side shell plating

5 Deck structure arrangement 40

5.1 General5.2 Opening arrangement5.3 Hatch supporting structure5.4 Pillars arrangement under deck

6 Bulkhead structure arrangement 41

6.1 General6.2 Watertight bulkheads6.3 Non-tight bulkheads6.4 Corrugated bulkheads6.5 Bulkhead acting as pillars6.6 Bracketed stiffeners

7 Superstructures and deckhouses structure arrangement 42

7.1 Connection of superstructures and deckhouses with the hull structure7.2 Structural arrangement of superstructures and deckhouses 7.3 Strengthening of deckhouse in way of tenders and liferafts


Section 2 Subdivision, Compartment Arrangement and Arrangement of Hull Openings

1 General 43

1.1 Application

2 Definition 43

2.1 Load line length2.2 Machinery spaces of category A

3 Subdivision arrangement 43

3.1 Number of transverse watertight bulkheads3.2 Water ingress detection3.3 Collision bulkhead3.4 After peak, machinery space bulkheads and stern tubes3.5 Height of transverse watertight bulkheads other than collision bulkhead and

after peak bulkheads3.6 Openings in watertight bulkheads and decks for ships with service notation

other than passenger ship or ro-ro passenger ship

4 Compartment arrangement 46

4.1 Definitions4.2 Cofferdam arrangement4.3 Double bottom4.4 Compartments forward of the collision bulkhead4.5 Minimum bow height4.6 Shaft tunnels4.7 Watertight ventilators and trunks4.8 Fuel oil tanks

5 Access arrangement 47

5.1 General5.2 Double bottom5.3 Access arrangement to and within spaces in, and forward of, the cargo area5.4 Shaft tunnels5.5 Access to steering gear compartment

Section 3 Scantling Criteria

1 General 49

1.1 Application1.2 Global and local stress 1.3 Stress notation

2 Steel and aluminium alloy structures 49

2.1 Permissible stresses for structure

3 Composite materials structure 51

3.1 General3.2 Rules safety factors3.3 Additional consideration on rules safety factor

4 Plywood structure 52

4.1 General4.2 Rules safety factor


CHAPTER 3DESIGN LOADS

Section 1 General1 Application 57

1.1 General

2 Definition 57

2.1 Hull girder loads2.2 Local external pressures2.3 Local internal pressures and forces

3 Local pressure application 57

3.1 Application

4 Local load point location 58

4.1 General case for structure made of steel and aluminium alloys4.2 General case for structure made of composite materials4.3 Superstructure and deckhouses

Section 2 Hull Girder Loads1 General 59

1.1 Hull girder loads

2 Calculation convention 59

2.1 Sign conventions of global bending moments and shear forces2.2 Designation of global bending moments and shear forces

3 Combination of hull girder loads 60

3.1 Hull girder loads combination3.2 Hull girder loads distribution

4 Still water loads 60

4.1 Cargo ship4.2 Non-cargo ship

5 Wave loads 61

5.1 General5.2 Wave loads in head sea condition5.3 Wave loads in quartering sea for multihull

6 Additional specific wave hull girder loads 64

6.1 Additional wave loads for high speed ship in planing mode6.2 Additional wave loads for multihull

Section 3 Local External Pressures1 General 66

1.1 Sea pressures1.2 Dynamic loads


2 Sea pressures 67

2.1 Ship relative motions2.2 Sea pressures

3 Dynamic loads 68

3.1 Side shell impact and platform bottom impact3.2 Bottom impact pressure for flat bottom forward area3.3 Bottom slamming for high speed ship

Section 4 Local Internal Pressures and Forces

1 Application 73

1.1 General

2 Ship accelerations 73

2.1 Reference values2.2 Vertical accelerations

3 Internal loads 74

3.1 Liquids3.2 Dry cargoes3.3 Wheeled loads

4 Loads on deck 76

4.1 Exposed deck4.2 Accommodation deck4.3 Specific loads on deck

5 Testing loads 77

5.1 General

6 Flooding loads 77

6.1 General


CHAPTER 4HULL SCANTLING

Section 1 General

1 Materials 81

1.1 General

2 Structure scantling approach 81

2.1 General2.2 Global strength analysis2.3 Local scantling analysis2.4 Specific cases

Section 2 Global Strength Analysis

1 General 82

1.1 Application1.2 Global strength calculation

2 Global strength check 82

2.1 General2.2 Maximum stress check2.3 Buckling check

3 Calculation of global strength for monohull ship 83

3.1 General3.2 Strength characteristics3.3 Overall stresses

4 Calculation of global strength of multihull 84

4.1 General4.2 Global strength in head sea condition4.3 Global strength of multihull in quartering sea and in digging in waves4.4 Transverse bending moment acting on twin-hull connections of swath

Section 3 Local Plating Scantling

1 General 88

1.1 General1.2 Local loads

2 Plating scantling 88

2.1 General2.2 Scantling for steel and aluminium plating2.3 Scantling for composite panel


Section 4 Local Secondary Stiffener Scantling

1 General 91

1.1 Local scantling1.2 Local loads1.3 Section modulus calculation1.4 End stiffener conditions for section moduli calculation1.5 Span of stiffener

2 Secondary stiffener scantling 93

2.1 General2.2 Scantling for steel and aluminium secondary stiffener2.3 Scantling of secondary stiffeners in composite materials

Section 5 Local Primary Stiffener Scantling

1 General 96

1.1 Local scantling1.2 Structural beam models1.3 Finite element model1.4 Beam section modulus calculation1.5 End stiffener conditions for calculation

2 Primary stiffener scantling 97

2.1 Scantling for steel and aluminium primary stiffeners under lateral loads2.2 Scantling for steel and aluminium primary stiffeners under wheeled loads2.3 Primary stiffeners in composite materials

3 Specific requirements 98

3.1 General3.2 Cut-outs and large openings 3.3 Web stiffening arrangement for primary supporting members

Section 6 Stiffener Brackets Scantling and Stiffener End Connections

1 General arrangement of brackets 101

1.1 Materials1.2 General requirements

2 Bracket for connection of perpendicular stiffeners 101

2.1 General arrangement

3 Bracket ensuring continuity of secondary stiffeners 102

3.1 General

4 Bracketless end stiffeners connections 103

4.1 Bracketless end connections4.2 Other type of end connection


Section 7 Pillar Scantling

1 General 104

1.1 Materials1.2 Application

2 Pillar in steel material 105

2.1 Buckling of pillars subjected to compression axial load2.2 Buckling of pillars subjected to compression axial load and bending moments2.3 Vertical bulkhead stiffener acting as pillar

3 Pillar in aluminium material 106

3.1 General

4 Pillar in composite material 106

4.1 Global column buckling4.2 Local buckling

Appendix 1 Calculation of the Critical Buckling Stresses

1 General 107

1.1 Application1.2 Materials

2 Plating 107

2.1 Calculation hypothesis

3 Secondary stiffeners 109


4 Primary stiffeners 110



CHAPTER 5OTHER STRUCTURES

Section 1 Superstructures and Deckhouses

1 General 113

1.1 Application1.2 Definitions1.3 Superstructures and deckhouses structure arrangement

2 Design loads 114

2.1 Load point 2.2 Lateral pressure on superstructure and deckhouse walls2.3 Pressures on superstructure decks

3 Plating 115

3.1 General3.2 Plating scantling

4 Ordinary stiffeners 115

4.1 General4.2 Ordinary stiffener scantling

5 Primary stiffeners 116

5.1 General

6 Arrangement of superstructures and deckhouses openings 116

6.1 General6.2 External openings

7 Sidescuttles, windows and skylights 116

7.1 General7.2 Opening arrangement7.3 Glasses7.4 Deadlight arrangement glasses

8 Door arrangements 119

8.1 General

Section 2 Other Structures

1 Fore part structure 120

1.1 General1.2 Stems1.3 Reinforcements of the flat bottom forward area1.4 Bow flare1.5 Bulbous bow1.6 Thruster tunnel

2 Aft part structure 121

2.1 General2.2 After peak2.3 Other structures


3 Machinery spaces 122

3.1 Application3.2 General3.3 Double bottom3.4 Single bottom3.5 Side3.6 Platforms3.7 Pillaring3.8 Machinery casing3.9 Seatings of main engines

4 Bow doors and inner doors 123

4.1 General4.2 Scantling and arrangement4.3 Securing and locking arrangement4.4 Operating and Maintenance Manual

5 Side doors and stern doors 124

5.1 General5.2 Scantling and arrangement5.3 Securing and locking arrangement5.4 Operating and Maintenance Manual

6 Hatch covers 124

6.1 Small hatch covers6.2 Large hatch covers

7 Movable decks and inner ramps - External ramps 125

7.1 Application7.2 Scantling7.3 Primary supporting members7.4 Supports, suspensions and locking devices7.5 Tests and trials7.6 External ramps

8 Rudders 126

8.1 General8.2 Rudder horn and solepiece scantlings

9 Water jet propulsion tunnel 127

9.1 General

10 Foils and trim tab supports 128

10.1 General

11 Propeller shaft brackets 128

11.1 General

12 Bulwarks 128

12.1 General

13 Lifting appliances 128

13.1 General

14 Protection of metallic hull 129

14.1 General


Section 3 Helicopter Decks and Platforms

1 Application 130

1.1 General1.2 Definition

2 General arrangement 130

2.1 Landing area and approach sector2.2 Sheathing of the landing area2.3 Safety net 2.4 Drainage system2.5 Deck reinforcements

3 Design loads 130

3.1 Emergency landing load3.2 Garage load3.3 Specific loads for helicopter platforms3.4 Local external pressures

4 Scantlings 131

4.1 Plating4.2 Ordinary stiffeners4.3 Primary supporting members

Section 4 Additional Requirements in Relation to the Service Notation or Service Feature Assigned to the Ship

1 General 133

1.1 Service notations and service features1.2 Material

2 Ro-ro cargo ships 133

2.1 Application2.2 General2.3 Hull scantlings

3 Container ships 134

3.1 Application3.2 General3.3 Structure design principles3.4 Design loads3.5 Hull scantlings3.6 Construction and testing

4 Livestock carriers 135

4.1 Application4.2 Ship arrangement4.3 Hull girder strength and hull scantlings

5 Bulk carriers 135

5.1 Application5.2 Ship arrangement5.3 Structure design principles5.4 Design loads5.5 Hull scantlings


5.6 Hatch covers5.7 Protection of hull metallic structure5.8 Construction and testing

6 Ore carriers 136

6.1 Application6.2 Ship arrangement6.3 Structure design principles6.4 Design loads6.5 Hull scantlings6.6 Hatch covers6.7 Construction and testing

7 Combination carriers 137

7.1 Application7.2 Ship arrangement7.3 Structure design principles7.4 Design loads7.5 Hull scantlings7.6 Other structures7.7 Hatch covers7.8 Protection of hull metallic structures7.9 Cathodic protection of tanks7.10 Construction and testing

8 Oil tankers and FLS tankers 138

8.1 Application8.2 Ship arrangement8.3 Design loads8.4 Hull scantlings8.5 Other structures8.6 Protection of hull metallic structure8.7 Cathodic protection of tanks8.8 Construction and testing

9 Chemical tankers 139

9.1 Application9.2 Ship survival capability and location of cargo tanks9.3 Ship arrangement9.4 Cargo containment9.5 Other structures9.6 Protection of hull metallic structure9.7 Construction and testing

10 Tankers 139

10.1 Application10.2 Ship arrangement10.3 Design loads10.4 Hull scantlings10.5 Other structures

11 Passenger ships 140

11.1 Application11.2 Ship arrangement11.3 Design loads11.4 Hull scantlings11.5 Other structures


12 Ro-ro passenger ships 141

12.1 Application12.2 Ship arrangement12.3 Structure design principles 12.4 Design loads12.5 Hull scantlings12.6 Other structures

13 Tugs 141

13.1 Application13.2 Structure design principles13.3 Hull scantlings13.4 Other structures13.5 Towing arrangements13.6 Construction and testing13.7 Additional requirements for salvage tugs, for escort tugs and for anchor handling

vessels 13.8 Integrated tug/barge combination

14 Supply vessels 142

14.1 Application14.2 Ship arrangement 14.3 Access arrangement14.4 Structure design principles14.5 Design loads14.6 Hull scantlings14.7 Other structure14.8 Hull outfitting

15 Fire-fighting ships 143

15.1 Application15.2 Structure design principles15.3 Other structures

16 Oil recovery ships 143

16.1 Application16.2 Ship arrangement16.3 Hull scantlings16.4 Construction and testing

17 Cable-laying ships 144

17.1 Application17.2 Hull scantlings17.3 Other structures17.4 Equipment

18 Non-propelled units 144

18.1 Application18.2 Structure design principles18.3 Hull girder strength18.4 Hull scantlings18.5 Hull outfitting

19 Fishing vessels 145

19.1 Application19.2 Ship arrangement19.3 Hull scantling


19.4 Specific design loads19.5 Hull scantlings19.6 Lifting appliances and fishing devices19.7 Hull outfitting19.8 Protection of hull metallic structure

20 Launch and seagoing launch 148

20.1 Application20.2 Hull outfitting

Section 5 Anchoring Equipment and Shipboard fittings for Anchoring, Mooring and Towing Equipment

1 Design assumption for anchoring equipment 149

1.1 General1.2 General case1.3 Specific cases

2 Anchoring equipment calculation 150

2.1 General2.2 Anchoring force calculation for monohull2.3 Anchoring force calculation for multihull

3 Equipment in chain and anchor 151

3.1 Anchors3.2 Chain cables3.3 Wire ropes and synthetic fibre ropes 3.4 Attachment pieces

4 Shipboard fittings for anchoring equipment 154

4.1 Windlass and chain stopper4.2 Chain locker4.3 Anchoring sea trials

5 Shipboard fittings for towing and mooring 155

5.1 General


CHAPTER 6CONSTRUCTION AND TESTING

Section 1 General1 General 159

1.1

2 Welding, welds and assembly of structure 1592.1 Material

3 Testing 1593.1 General

4 Construction survey 1594.1 General

Section 2 Welding for Steel1 General 160

1.1 Materials1.2 Application1.3 Weld and welding booklet

2 Scantling of welds 1602.1 Butt welds2.2 Butt welds on permanent backing2.3 Fillet weld on a lap-joint2.4 Slot welds2.5 Plug welding2.6 Fillet weld

3 Typical joint preparation 1643.1 General3.2 Butt welding3.3 Fillet weld

4 Plate misalignment 1664.1 Misalignment in butt weld4.2 Misalignment in cruciform connections

Section 3 Testing1 General 167

1.1 Application1.2 Definitions

2 Watertight compartments 1672.1 General2.2 Structural testing2.3 Hydropneumatic testing2.4 Leak testing2.5 Hose testing2.6 Other testing methods


3 Miscellaneous 170

3.1 Watertight decks, trunks, etc.3.2 Doors in bulkheads above the bulkhead deck3.3 Steering nozzles3.4 Working test of windlass

Section 4 Construction Survey

1 General 171

1.1 Scope

2 Structure drawing examination 171

2.1 General

3 Hull construction 171

3.1 Shipyard details and procedures3.2 Materials3.3 Forming3.4 Welding3.5 Inspection and check3.6 Modifications and repairs during construction

4 Survey for unit production 175

4.1 General

5 Alternative survey scheme for production in large series 175

5.1 General5.2 Type approval5.3 Quality system documentation5.4 Manufacturing, testing and inspection plan (MTI plan)5.5 Society’s certificate


NR 600

Chapter 1

GENERAL

SECTION 1 GENERAL

SECTION 2 MATERIALS

SECTION 3 SCANTLING PRINCIPLE


NR 600, Ch 1, Sec 1

SECTION 1 GENERAL

1 General

1.1 Wording

1.1.1 Rules

In the present Rules, references to other Rules of the Societyare defined in Tab 1.

Table 1 : References to other Rules of the Society

1.1.2 Ship group: Cargo ships and non-cargo ships

The wording “cargo ships” and “no-cargo ships” used in thepresent Rules means:

• Cargo ships: ships liable to carry cargoes and having adeadweight greater than 30% of the total displacement.As a general rule, these ships are fitted with cargo holds,tanks and ballast tanks (i.e bulk or ore carriers, oil orchemical tanker, container ship, general cargo ship, ...)and the value of the block coefficient is greater than0,75.

• Non-cargo ships: type of ships other than cargo shipsdefined here above.

1.1.3 Multihull

The wording “multihull” used in the present Rules meansship with two hulls connected to a platform structure.

Multihull with more than two floats are to be considered ona case-by-case basis.

The two types of multihull considered in the present Rulesare:

• Catamaran:

Multihull which may be of displacement hull type or inplaning hull type according to its design

• Swath (small waterplane area twin hull ship):

Multihull with two submerged floats connected to theplatform structure by narrow struts.

As a rule, swath are not to be considered as high speedship having a planing hull and are not subjected toslamming impacts on bottom.

1.1.4 High speed ship

The wording “high speed ships” used in the present Rulesmeans ships having a planning hull and able to sail:

• in planing mode in adapted sea state to reach its maxi-mum speed, resulting in slamming phenomenon on bot-tom, and

• in displacement mode without any restricted weatherconditions.

The Designer is to define if the ship is a high speed shiphaving a hull shape of a planing hull type and if bottomslamming impacts is expected to occur.

High speed ships for which V ≥ 10 LWL0,5 are individually

considered by the Society.

Note 1: As a guidance, a ship may be considered as able to sail inplaning hull mode at high speed when:

V : Speed of the ship, in knots

Δ : Displacement of the ship, in tonnes.

Note 2: Ships having the service notation light ship or HSC are notcovered by the present Rules and are to meet the requirements ofNR396 Unitas “High Speed Craft Rules”.

1.2 Classification

1.2.1 General

Ships complying with the requirements of the present Rulesare to comply with the requirements of NR467 Steel Ships,Part A (Classification and survey).

1.2.2 Service notation or additional features

In addition to the present Rules and especially Ch 5, Sec 4,additional requirements of NR467 Steel Ships, Part D are tobe considered in relation to the service notations or addi-tional service features assigned to the ship.

1.2.3 Additional class notation

In addition to the present Rules, additional requirements ofNR467 Steel Ships, Part E are to be considered in relation tothe additional class notations requested by the InterestedParty.

Reference Rules

NR467 Steel Ships

Rules for the Classification of SteelShips

NR566 Hull Arrangement, Stability andSystems for ships less than 500 GT

NR546 Composite Ships

Rules for Hull in Composite Materialsand Plywood, Material Approval,Design Principles, Construction andSurvey

NR561 Aluminium Ships

Rules for Hull in Aluminium Alloys,Design Principles, Construction andSurvey

NR216 Materials & Welding

Rules on Materials and Welding forthe Classification of Marine Units

V 7 16Δ1 6⁄,≥


NR 600, Ch 1, Sec 1

2 Application criteria

2.1 Type of ship covered by the present Rules

2.1.1 General

The present Rules contain the requirements for the determi-nation of the hull scantlings (for the fore, central and aft partsof the ship) and structure arrangement applicable to the fol-lowing type of ships of normal form, speed and proportionsand built in steel, aluminium, or composite materials:

• cargo ships with L less than 65 m

• non-cargo ships with L less than 90 m.

2.1.2 Additional requirements applicable to specific ships

a) Ship in aluminium

Specific additional requirements applicable to shipsbuilt in aluminium materials are defined in NR561 Alu-minium Ships.

b) Ship in composite materials

Specific additional requirements applicable to shipsbuilt in composite and/or plywood materials are definedin NR546 Composite Ships.

2.2 Ship types not covered by the present Rules

2.2.1 Liquefied gas carrier

Ships having the service notation liquefied gas carrier arenot covered by the present Rules and are to be in accord-ance with NR467 Steel Ships, Part B and Part D, Chapter 9.

2.2.2 Ships for dredging activity

Ships having one of the following service notations are notcovered by the present Rules and are to be in accordancewith NR467 Steel Ships, Part B and Part D, Chapter 13:

• dredger

• hopper dredger

• hopper unit

• split hopper dredger

• split hopper unit.

2.2.3 Cargo ships with alternate light and heavy cargo loading conditions

As a rule, for ships having alternate light and heavy cargoloading conditions, the scantlings may be checked accord-ing to NR467 Steel Ships, Part B, Chapter 7 instead of thepresent Rules when deemed necessary by the Society.

2.3 Particular cases

2.3.1 Hull scantling

The Society reserves its right, whenever deemed necessary,to fully apply the requirements defined in NR467 SteelShips (dedicated for ships greater than 65 m in rule length)instead of the present Rules (see Sec 3, [2]).

2.3.2 Subdivision, compartment arrangement, and arrangement of hull openings

The requirements to be applied for the subdivision of thehull, the compartment arrangements and the arrangementof hull openings are defined in Ch 2, Sec 2, Tab 1.

3 Navigation coefficients

3.1 Navigation notation

3.1.1 The navigation coefficients n and n1, which appear inthe formulae of the present Rules, are defined in Tab 2depending on the assigned navigation notation defined inNR467 Steel Ships, Pt A, Ch 1, Sec 2, [5.1].

Table 2 : Navigation coefficients n and n1

3.2 Sea going launch and launch

3.2.1 For the service notations sea going launch and launchas defined in NR467 Steel Ships, Pt A, Ch 1, Sec 2, [4.11.2],the navigation coefficients n and n1, which appear in the for-mulae of the present Rules, are defined in Tab 3.

Table 3 : Navigation coefficients n and n1

4 Definitions

4.1 Length

4.1.1 Rule length

Rule length L is equal to the distance, in m, measured onthe summer load waterline, from the fore-side of the stem tothe after side of the rudder post, or to the centre of the rud-der stock where there is no rudder post. L is to be not lessthan 96% and need not exceed 97% of the extreme lengthon the summer load waterline.

Navigation notationn for local scantling

n1 for hull girder scantling

unrestricted navigation 1,00 1,00

summer zone 0,90 0,95

tropical zone 0,80 0,90

coastal area 0,80 0,90

sheltered area 0,65 0,80

Service notationn for local scantling

n1 for hull girder scantling

sea going launch 0,65 + 0,008 Lw ≤ 1 0,80

launch 0,55 + 0,008 Lw ≤ 1 0,70

Note 1:Lw : Lw = 0,5 (LWL + LHULL)where:LWL : Length at waterline at full load, in mLHULL : Length of the hull from the extreme forward to

the extreme aft part of the hull, in m.


NR 600, Ch 1, Sec 1

4.1.2 Ends of the rule length

The fore end (FP) of the rule length L is the perpendicular tothe summer load waterline at the forward side of the stem.

The aft end (AP) of the rule length L is the perpendicular tothe waterline at a distance L aft of the fore end.

4.1.3 Midship LCG

The midship LCG is the perpendicular to the waterline at adistance 0,5 L aft of the fore end.

4.1.4 Load line length

The load line length LLL is the distance, in m, on the water-line at 85% of the least moulded depth from the top of thekeel, measured from the forward side of the stem to the cen-tre of the rudder stock. LLL is to be not less than 96% of thetotal length on the same waterline.

In ship design with a rake of keel, the waterline on whichthis length is measured is parallel to the designed waterlineat 85% of the least moulded depth Dmin found by drawing aline parallel to the keel line of the ship (including skeg) tan-gent to the moulded sheer line of the freeboard deck.Theleast moulded depth is the vertical distance measured fromthe top of the keel to the top of the freeboard deck beam atside at the point of tangency (see Fig 1).

Figure 1 : Length of ships with a rake of keel

4.1.5 Hull length

The hull length LHULL is equal to the distance, in m, meas-ured vertically from the fore end of the hull to the aft end ofthe hull.

4.1.6 Waterline length

The waterline length LWL is equal to the distance, in m,measured vertically from the intersection between thewaterline at full load displacement and the fore end and aftend of the hull.

4.2 Breadth

4.2.1 Moulded breadth

The moulded breadth B is the greatest moulded breadth, inm, measured amidships below the weather deck.

4.2.2 Waterline breadth

The waterline breadth BWL is the breadth, in m, measuredamidships at the moulded draught.

For catamaran, the waterline breadth BWL is to be measuredat one float at moulded draught.

For swath, the waterline breadth BST is to be measured atone strut at moulded draught.

4.2.3 Breadth between multihull floatsThe breadth between floats BE is the distance, in m, measuredbetween the longitudinal planes of symmetry of the floats.

4.2.4 Breadth of submerged float of swathThe moulded breadth of submerged float of swath BSF is thegreatest moulded breadth, in m, measured amidships of thesubmerged float.

4.3 Depth

4.3.1 The depth D is the distance, in m, measured verti-cally on the midship transverse section, from the mouldedbase line to the top of the deck beam at side on the upper-most continuous deck.In the case of a ship with a solid bar keel, the moulded baseline is to be taken at the intersection between the upperface of the bottom plating with the solid bar keel at the mid-dle of length L.

4.4 Moulded draught

4.4.1 The moulded draught T is the distance, in m, meas-ured vertically on the midship transverse section, from themoulded base line to the summer load line.In the case of ships with a solid bar keel, the moulded baseline is to be taken as defined for the measurement of thedepth.

4.5 Total block coefficient

4.5.1 The total block coefficient is to be taken equal to:• For monohull:

• For catamaran:

• For swath:

where:Bm = (BSF DSF + BST (T − DSF)) / T

with: BSF : Breadth, in m, of the submerged floatDSF : Depth, in m, of the submerged floatBST : Breadth, in m, of the strutT : Moulded draught, in m.

4.6 Chine and bottom

4.6.1 ChineFor hulls that do not have a clearly identified chine, thechine is the hull point at which the tangent to the hull isinclined 50° to the horizontal.

4.6.2 BottomThe bottom is the part of the hull between the keel and thechines.

� ��

��

� ��

�� CB

Δ1 025LWLBWLT,---------------------------------------=

CBΔ

1 025LWL2BWLT,-------------------------------------------=

CBΔ

1 025LWL2BmT,----------------------------------------=


NR 600, Ch 1, Sec 1

4.7 Lightweight

4.7.1 The lightweight is the displacement, in t, withoutcargo, fuel, lubricating oil, ballast water, fresh water andfeed water, consumable stores and passengers and crewand their effects, but including liquids in piping.

4.8 Deadweight

4.8.1 The deadweight is the difference, in t, between thedisplacement, at the summer draught in sea water of densityρ = 1,025 t/m3, and the lightweight.

4.9 Freeboard deck

4.9.1 The freeboard deck is defined in Regulation 3 of the1966 International Convention on Load Lines, as amended.

4.10 Bulkhead deck

4.10.1 The bulkhead deck in a passenger ship means theuppermost deck at any point in the subdivision length LS towhich the main bulkheads and the ship’s shell are carriedwatertight. In a cargo ship the freeboard deck may be takenas the bulkhead deck.

4.11 Superstructure

4.11.1 General

A superstructure is a decked structure connected to the free-board deck, extending from side to side of the ship or withthe side plating not being inboard of the shell plating morethan 0,04 B.

4.11.2 Superstructure deck

A superstructure deck is a deck forming the upper boundaryof a superstructure.

4.11.3 Deckhouse

A deckhouse is a decked structure other than a superstruc-ture, located on the freeboard deck or above.

4.11.4 Standard height of superstructure

The standard height of superstructure is defined in Tab 4.

Table 4 : Standard height of superstructure

4.11.5 Tiers of superstructure and deckhouse

The lowest tier is the tier located immediately above thefreeboard deck.

The second tier is the tier located immediately above thelowest tier, and so on.

4.12 Platform of multihull

4.12.1 A platform of multihull is a strength structure con-necting the hulls by primary cross transverse structure ele-ment. These transverse elements may be cross beams orcross bulkheads. The part of the platform directly exposed to sea effect isdesigned as platform bottom.

The upper part of the platform and the upper decks aredefined as platform deck.

5 Reference co-ordinate system

5.1 General

5.1.1 The ship’s geometry, motions, accelerations and loadsare defined with respect to the following right-hand co-ordi-nate system (see Fig 2):• Origin: at the intersection among the longitudinal plane

of symmetry of ship, the aft end of L and the baseline• X axis: longitudinal axis, positive forwards• Y axis: transverse axis, positive towards portside• Z axis: vertical axis, positive upwards.

5.1.2 Positive rotations are oriented in anti-clockwisedirection about the X, Y and Z axes.

Figure 2 : Reference co-ordinate system

6 Stability

6.1 General

6.1.1 For information, intact stability and damage stabilityare to comply with the following Rules:• For non-propelled ships and ships of less than 500 GT:

- passenger ship with unrestricted navigation: NR467Steel Ships

- ro-ro passenger ship with unrestricted navigation:NR467 Steel Ships

- chemical tanker: NR467 Steel Ships- fishing vessel: NR467 Steel Ships- other ship service notations: NR566

• For ships of 500 GT and over:NR467 Steel Ships.

Load line length LLL

in m

Standard height hS, in m

Raised quarter deck

All othersuperstructures

LLL ≤ 30 0,90 1,80

30 < LLL < 75 0,9 + 0,00667 (LLL − 30) 1,80

75 ≤ LLL < 90 1,2 + 0,012 (LLL − 75) 1,8 + 0,01 (LLL − 75)

�

�

��

�


NR 600, Ch 1, Sec 1

7 Documentation to be submitted

7.1 Documentation to be submitted

7.1.1 Plans and documents to be submitted for approval

a) GeneralThe plans and documents to be submitted to the Societyfor approval are listed in Tab 5.Structural plans are to show details of connections ofthe various parts and are to specified the materials used,including their manufacturing processes (see also Chap-ter 6).

b) Service notationThe plans and documents in relation to the service nota-tion to be submitted to the Society for approval arelisted in Tab 6.

c) Additional class notation

The plans and documents in relation to the additionalclass notation to be submitted to the Society forapproval are listed in Tab 7.

7.1.2 Plans and documents to be submitted for information

In addition to those in [7.1.1], the following plans and doc-uments are to be submitted to the Society for information:

• general arrangement

• capacity plan, indicating the volume and position of thecentre of gravity of all compartments and tanks

• lightweight distribution.

In addition, when direct calculation analyses are carried outby the Designer according to the rule requirements, theyare to be submitted to the Society.

Table 5 : Plans and documents to be submitted for approval for all ships

Plan or document Containing also information on

Midship sectionTransverse sectionsShell expansionDecks and profilesDouble bottomPillar arrangementsFraming planDeep tank and ballast tank bulkheads, swashbulkheads

Class characteristicsMain dimensionsMinimum ballast draughtFrame spacingContractual service speedDensity of cargoesDesign loads on decks and double bottomSteel gradesLocation and height of air vent outlets of various compartmentsCorrosion protectionOpenings in decks and shell and relevant compensationsBoundaries of flat areas in bottom and sidesDetails of structural reinforcements and/or discontinuitiesBilge keel with details of connections to hull structures

Watertight subdivision bulkheadsWatertight tunnels

Openings and their closing appliances, if any

Fore part structure Location and height of air vent outlets of various compartments

Transverse thruster, if any, general arrangement,tunnel structure, connections of thruster withtunnel and hull structures

Aft part structure Location and height of air vent outlets of various compartments

Machinery space structuresFoundations of propulsion machinery and boilers

Type, power and r.p.m. of propulsion machineryMass and centre of gravity of machinery and boilers

Superstructures and deckhousesMachinery space casing

Extension and mechanical properties of the aluminium alloy used (where applicable)

Bow doors, stern doors and inner doors, if any,side doors and other openings in the side shell

Closing appliancesElectrical diagrams of power control and position indication circuits for bowdoors, stern doors, side doors, inner doors, television system and alarm systemsfor ingress of water

Hatch covers, if any Design loads on hatch coversSealing and securing arrangements, type and position of locking boltsDistance of hatch covers from the summer load waterline and from the fore end

Movable decks and ramps, if any

(1) Where other steering or propulsion systems are adopted (e.g. steering nozzles or azimuth propulsion systems), the plans show-ing the relevant arrangement and structural scantlings are to be submitted.


NR 600, Ch 1, Sec 1

Table 6 : Plans and documents to be submitted depending on service notations

Windows and side scuttles, arrangements anddetails

Bulwarks and freeing ports Arrangement and dimensions of bulwarks and freeing ports on the freeboarddeck and superstructure deck

Helicopter decks, if any General arrangementMain structureCharacteristics of helicopters: maximum mass, distance between landing gearsor landing skids, print area of wheels or skids, distribution of landing gear loads

Rudder and rudder horn (1) Maximum ahead service speed

Stern frame or sternpost, stern tube (1)Propeller shaft boss and brackets

Derricks and cargo gearCargo lift structures

Design loads (forces and moments)Connections to the hull structures

Sea chests, stabiliser recesses, etc.

Hawse pipes

Plan of outer doors and hatchways

Plan of manholes

Plan of access to and escape from spaces

Plan of tank testing Testing procedures for the various compartmentsHeight of pipes for testing

Plan of watertight doors and scheme of relevantmanoeuvring devices

Manoeuvring devicesElectrical diagrams of power control and position indication circuits

Equipment number calculation Geometrical elements for calculationList of equipmentConstruction and breaking load of steel wiresMaterial, construction, breaking load and relevant elongation of synthetic ropes

Service notations (1) Plans or documents

Ro-ro passenger shipRo-ro cargo ship

Plans of the bow or stern ramps, elevators for cargo handling and movable decks, if any, including:• structural arrangements of ramps, elevators and movable decks with their masses• arrangements of securing and locking devices• connection of ramps, lifting and/or hoisting appliances to the hull structures, with indication of design

loads (amplitude and direction)• wire ropes and hoisting devices in working and stowed position• hydraulic jacks• loose gear (blocks, shackles, etc.) indicating the safe working loads and the testing loads• test conditionsOperating and maintenance manual of bow and stern doors and rampsPlan of arrangement of motor vehicles, railway cars and/or other types of vehicles which are intended to becarried and indicating securing and load bearing arrangementsCharacteristics of motor vehicles, railways cars and/or other types of vehicles which are intended to be car-ried: (as applicable) axle load, axle spacing, number of wheels per axle, wheel spacing, size of tyre print Plan of dangerous areas, in the case of ships intended for the carriage of motor vehicles with petrol in their tanks

Container ship Container arrangement in holds, on decks and on hatch covers, indicating size and gross mass of containersContainer lashing arrangement indicating securing and load bearings arrangementsDrawings of load bearing structures and cell guides, indicating the design loads and including the connec-tions to the hull structures and the associated structural reinforcements

(1) as defined in NR467 Steel Ships, Part A.

Plan or document Containing also information on

(1) Where other steering or propulsion systems are adopted (e.g. steering nozzles or azimuth propulsion systems), the plans show-ing the relevant arrangement and structural scantlings are to be submitted.


NR 600, Ch 1, Sec 1

Table 7 : Plans and documents to be submitted depending on additional class notations

Livestock carrier Livestock arrangementDistribution of fodder and consumable liquid on the various decks and platforms

Oil tanker ESPFLS tanker

Arrangement of pressure/vacuum valves in cargo tanksCargo temperatures

Tanker Cargo temperatures

Chemical tanker List of cargoes intended to be carried, with their densityTypes of cargo to be carried in each tankCargo temperatures Arrangement of pressure/vacuum valves in cargo tanksFor ships with independent tanks, connection of the cargo tanks to the hull structure

TugSalvage tugTug escort

Connection of the towing system (winch and hook) with the hull structures with indication of design loads

Tug, Salvage tug, Tug escort with additional service feature barge combined

Structural arrangement of the fore part of the tug, showing details of reinforcements in way of the connect-ing point Structural arrangement of the aft part of the barge, showing details of reinforcements in way of the connect-ing point Details of the connection systemBarge with additional

service feature tug combined

Supply vessel General plan showing the location of storage and cargo tanks with adjacent cofferdams and indicating thenature and density of cargoes intended to be carriedPlan of gas-dangerous spacesConnection of the cargo tanks with the hull structureStowage of deck cargoes and lashing arrangement with location of lashing points and indication of design loadsStructural reinforcements in way of load transmitting elements, such as winches, rollers, lifting appliances

Oil recovery ship General plan showing the location of tanks intended for the retention of oily residues and systems for theirtreatmentPlan of the system for treatment of oily residues and specification of all relevant apparatusesSupporting structures of the system for treatment of oily residuesOperating manual

Cable laying ship Structural reinforcements in way of load transmitting elements, such as foundations and fastenings of theequipment to the ship structures

Fishing vessel Minimum design temperature of refrigerated spacesStructural reinforcements in way of load transmitting elements, such as masts, gantries, trawl gallows andwinches, including the maximum brake load of the winches

Additional class notation (1) Plans or documents

ICE CLASS IA SUPERICE CLASS IAICE CLASS IBICE CLASS ICICE CLASS ID

The plans relevant to shell expansion and fore and aft part structures are to define the maximumdraught LWL, the minimum draught BWL (both draughts at midship, fore and aft ends), and the bor-derlines of fore, midship and aft regions (see NR467 Steel Ships, Part E, Chapter 8)

LASHING Lashing arrangement plans, indicating:• container arrangement in holds, on decks and on hatch covers, with specification of the gross

mass of each container and of each container stack• arrangement of mobile lashing equipment with the specific location of the various pieces of

equipmentComplete list of the mobile lashing equipment, with detailed drawing and indication of materials,safety working loads, breaking loads or test toadsRemovable load-bearing structures for containers, such as guides, cells, buttresses, etc., connected tothe hull structure or to hatch covers

(1) as defined in the NR467 Steel Ships, Part A.

Service notations (1) Plans or documents

(1) as defined in NR467 Steel Ships, Part A.


NR 600, Ch 1, Sec 2

SECTION 2 MATERIALS

1 General

1.1 Application

1.1.1 This Section defines the main characteristics to takeinto account for steels, aluminium alloys or compositematerials within the scope of the determination of the hullscantling as defined in the present Rules.

1.1.2 Materials and products such as parts made of ironcastings, where allowed, products made of copper and cop-per alloys, rivets, anchors, chain cables, cranes, masts, der-rick posts, derricks, accessories and wire ropes are tocomply with the applicable requirements of NR216 Materi-als and Welding.

1.1.3 Materials with different characteristics may be con-sidered, provided their specification (manufacture, chemi-cal composition, mechanical properties, welding, etc.) issubmitted to the Society for approval.

2 Steels for hull structure

2.1 General

2.1.1 Characteristics of materials

The characteristics of steels to be used in the construction ofships are to comply with the applicable requirements ofNR216 Materials and Welding.

2.1.2 Testing and manufacturing process

Materials are to be tested in compliance with the applicablerequirements of NR216 Materials and Welding.

The requirements of this Section presume that welding andother cold or hot manufacturing processes (parent materialtypes and welding, preheating, heat treatment after weld-ing, etc.) are carried out in compliance with current soundworking practice and the applicable requirements of NR216Materials and Welding.

2.1.3 Mechanical characteristics of hull steels

The mechanical characteristics of steels are to comply withthe requirements of NR467 Steel Ships, Pt B, Ch 4, Sec 1,and in particular the:

• grade of steel to be used for the various strength mem-bers of the structure

• grade of steel for structure exposed to low temperatures(air and/or refrigerated spaces)

• steels for forging and casting.

Table 1 : Mechanical properties of hull steels

Tab 1 gives the mechanical properties of steels currentlyused in the construction of ships as a reminder.

Higher strength steels other than those indicated in Tab 1are considered by the Society on a case-by-case basis.

When steels with a minimum specified yield stress ReH otherthan 235 N/mm2 are used on a ship, hull scantlings are tobe determined by taking into account the material factor kdefined in [2.1.4].

2.1.4 Material factor k for scantling

As a rule, the scantling of structure element is based on asteel material of minimum yield stress ReH equal to235 N/mm2.

A material factor k is used in the scantling formulae to takeinto account steel materials with other values of minimumyield stress.

Unless otherwise specified, the material factor k has the val-ues defined in Tab 2, as a function of the minimum speci-fied yield stress ReH.

For intermediate values of ReH , k may be obtained by linearinterpolation.

Steels with a yield stress lower than 235 N/mm2 or higherthan 390 N/mm2 are considered by the Society on a case-by-case basis.

Table 2 : Material factor k

Steel gradest ≤ 100 mm

Minimum yield stress ReH ,in N/mm2

Ultimate minimum tensile strength Rm ,

in N/mm2

A-B-D-E 235 400 - 520

AH32-DH32-EH32FH32

315 440 - 590

AH36-DH36-EH36FH36

355 490 - 620

AH40-DH40-EH40 FH40

390 510 - 650

Note 1: Refer to NR216 Materials and Welding, Ch 2, Sec 1,[2].

ReH , in N/mm2 k

235 1,00

315 0,78

355 0,72

390 0,68


NR 600, Ch 1, Sec 2

2.1.5 Minimum yield stress for scantling criteria of hull structure

The minimum yield stress of steel Ry , in N/mm2, used forthe scantling criteria of the hull structure is to be taken,unless otherwise specified, equal to:

where:

k : Material factor defined in [2.1.4].

3 Aluminium alloys for hull structure


3.1.1 The characteristics of aluminium alloys to be used inthe construction and their testing process are to complywith the applicable requirements of the following Rules:

• NR216 Materials and Welding

• NR561 Aluminium Ships.

Materials with different characteristics may be accepted,provided their specification (manufacture, chemical com-position, mechanical properties, welding, etc.) is submittedto the Society for approval.

3.1.2 Material factor k for scantling

As a rule, the scantling of structure element is based on analuminium alloy in welded condition of minimum yieldstress R’

lim equal to 100 N/mm2.

A material factor k, used on the scantling formula to takeinto account aluminium alloy in welded condition withother values of minimum yield stress, is to be taken equalto:

where:

R’lim : Minimum yield stress of the aluminium alloys

considered, to be taken equal to the minimumvalue, in welded condition, between R’

p0,2

(proof stress) and 0,7 R’m (tensile strength),

where R’p0,2 and R’

m are defined in NR561 Alu-minium Ships.

3.1.3 Minimum yield stress for scantling criteria of hull structure

The minimum yield stress of aluminium Ry , in N/mm2, usedfor the scantling criteria of the hull structure is to be taken,unless otherwise specified, equal to:

where:k : Material factor defined in [3.1.2].

4 Composite materials and plywood for hull structure


4.1.1 The characteristics of composite materials and ply-wood and their testing and manufacturing process are tocomply with the applicable requirements of NR546 Com-posite Ships, in particular for the:• raw materials• laminating process• mechanical tests and raw material homologation.

4.2 Application

4.2.1 Attention is drawn to the use of composite and/or ply-wood materials from a structural fire protection point ofview. The Flag Administration may request that international con-vention be applied instead of the present requirements,entailing in some cases a use limitation of composite and/orplywood materials.

Ry 235 k⁄=

k 100 R′l im⁄=

Ry 100 k⁄=


NR 600, Ch 1, Sec 3

SECTION 3 SCANTLING PRINCIPLES

Symbols

L : Rule length, in m, as defined in Sec 1, [4.1.1].

1 Main scantling principles

1.1 General

1.1.1 The present Section defines the main scantling princi-ples considered in the present Rules.

1.2 Type of ships

1.2.1 General

Two groups of ship are defined, taking into account specificshape of hull (see definition in Sec 1, [1.1.2]):

• Cargo ship

• Non-cargo ship.

Ship motions and accelerations of ship under examinationare calculated in relation to its group.

The longitudinal distribution of ship motions and accelera-tions along the ship length are defined on four differentareas, as follows (see Fig 1):

• 1st area: from aft part to 0,25 L

• 2nd area: from 0,25 L to 0,70 L

• 3rd area: from 0,70 L to 0,85 L

• 4th area: from 0,85 L to the fore part.

Ship motions and accelerations of each area are calculatedin the middle of the area and are considered as constantalong the area.

As a rule, ship motions and accelerations are calculated inhead sea condition.

Figure 1 : Definition of longitudinal areas

1.2.2 Specific case of high speed shipThe structure of the high speed ship with planing hull is tobe examined in the two following conditions of navigation:

• when the ship sails in a displacement mode:

as cargo or non-cargo ship, as applicable, and

• when the sea conditions allow to sail at the maximumcontractual speed in planing hull mode:

as a high speed ship.

The global and local loads, and the permissible stressesconsidered to check the structure are specific to each ofthese two conditions of navigation.

1.3 Corrosion addition

1.3.1 Steel shipsThe scantlings obtained by applying the criteria specified inthe present Rules for steel structure are gross scantling, i.e.they include additions for corrosion.

As a rule, the included corrosion additions are equal to:

• 15% of the local scantling of an individual plate ele-ment required to sustains the loads

• 20% of the local scantling of an individual stiffener ele-ment required to sustains the loads

• 10% of the local scantling of a set of element (plate orlongitudinal) contributing to the longitudinal globalstrength.

1.3.2 Aluminium shipsThe scantlings obtained by applying the criteria specified inthe present Rules for aluminium structure are gross scant-ling, i.e they include additions for local corrosion.

As a rule, the included corrosion additions is equal to 5% ofthe scantling required to sustains the loads.

1.3.3 Composite shipsThe scantlings obtained by applying the criteria specified inthe present Rules for composite structure include a rule par-tial safety coefficient, CV, taking into account the ageingeffect on the laminate mechanical characteristics.

1.4 Rounding off

1.4.1 The rounding off of plate thicknesses on metallichulls is to be obtained from the following procedure:

a) the thickness is calculated in accordance with the rulerequirements

b) the rounded thickness is taken equal to the valuerounded off to the nearest half-millimetre.L

1st area 2nd area 3rd area 4th area

0,25 L0,70 L

0,85 L


NR 600, Ch 1, Sec 3

Stiffener section moduli as calculated in accordance withthe rule requirements are to be rounded off to the neareststandard value. However, no reduction may exceed 3%.

2 Hull analysis approach

2.1 Hull girder and local strength

2.1.1 General

As a rule, the global hull girder strength and the localstrength are examined independently in the present Rules,as follows:

• the longitudinal scantling of the hull girder is examinedon the basis of a maximum permissible stress at deckand bottom and a buckling check of elements contribut-ing to the hull girder strength

• the local scantling is examined on the basis of local per-missible stresses defined in relation to the type of localloads applied and the type of structure element.

2.1.2 Particular case

As a rule, the requirements of NR467 Steel Ships,Chapter 7, dedicated for ships greater than 65 m, are to befully applied instead of the present Rules when:

• the global stress, in N/mm2, calculated according to Ch 4,Sec 2 (excluding the case of the minimum bendingmoment for high speed ship calculated according to Ch 3,Sec 2, [6.1]) is greater than 0,35 Ry, where Ry is defined inSec 2, [2.1.5] for steel structure and in Sec 2, [3.1.3] foraluminium structure.

• when deemed necessary by the Society.

For ship built in composite materials, a combination withthe global hull girder stresses for the local scantling analysismay be carried out when deemed necessary by the Society.

2.2 Plating scantling approach

2.2.1 GeneralThe plating scantlings obtained by applying the criteriaspecified in the present Rules are based on a simplify elasticbehaviour of plating under lateral loads approach.

2.2.2 Other plating scantling approachWhen deemed necessary, it may be considered a platingscantling approach based on a plastic behaviour of platingunder lateral loads.

In this case, the requirements of NR467 Steel Ships,Chapter 7, dedicated for ships greater than 65 m, are to befully applied, instead of the present Rules, to check the hullstructure.


NR 600, Ch 1, Sec 3


NR 600

Chapter 2

STRUCTURE DESIGN PRINCIPLES,GENERAL ARRANGEMENT AND

SCANTLING CRITERIA

SECTION 1 STRUCTURE DESIGN PRINCIPLES

SECTION 2 SUBDIVISION, COMPARTMENT ARRANGEMENT, AND ARRANGEMENT OF HULL OPENINGS

SECTION 3 SCANTLING CRITERIA


NR 600, Ch 2, Sec 1

SECTION 1 STRUCTURE DESIGN PRINCIPLES

1 General

1.1 Application

1.1.1 Steel structure

The requirements of the present Section apply to longitudi-nally or transversely frame structure arrangement of hullbuilt in steel materials for:

• structural continuity of hull

• single and double bottoms

• sides and decks

• transverse and longitudinal structures

• superstructures and deckhouses

• special features.

Any other arrangement may be considered on a case-by-case basis.

Additional specific structure design principles in relation tothe service notation of the ship are defined in Ch 5, Sec 4.

1.1.2 Aluminium structure

Equivalent arrangements for hull built in aluminium alloysare defined in NR561 Aluminium Ships.

1.1.3 Composite and plywood structure

Equivalent arrangements for hull built in composite materi-als and/or plywood are defined in NR546 Composite Ships.

2 Structural continuity of hull girder

2.1 General principles for longitudinal hull girder

2.1.1 Attention is to be paid to the structural continuity:

• in way of changes in the framing system

• at the connections of primary and secondary stiffeners.

2.1.2 Longitudinal members contributing to the hull girderlongitudinal strength are to extend continuously over a suf-ficient distance towards the ends of the ship.

Secondary stiffeners contributing to the hull girder longitu-dinal strength are generally to be continuous when crossingprimary supporting members. Otherwise, the detail of con-nections is considered by the Society on a case-by-casebasis.

2.1.3 Where stress concentrations may occur in way ofstructural discontinuity, adequate compensation and rein-forcements are to be provided.

2.1.4 Openings are to be avoided, as far as practicable, inway of highly stressed areas.

Where necessary, the shape of openings is to be speciallydesigned to reduce the stress concentration factors.

Openings are to be generally well rounded with smoothedges.

2.1.5 Primary supporting members are to be arranged insuch a way that they ensure adequate continuity of strength.Abrupt changes in height or in cross-section are to beavoided.

2.2 General principles for platform of multihull

2.2.1 Attention is to be paid to the structural continuity ofthe primary transverse cross structure of the platform ensur-ing the global transversal resistance of the multihull.

The primary transverse cross structure of catamaran are gen-erally to be continuous when crossing float structures.

The connection between the transverse cross structure ofswath and struts are to be examined by direct calculation.

The general continuity principles defined in [2.1] also applyfor the primary transverse cross structure of the platform.

2.3 Insert plates and doublers

2.3.1 A local increase in plating thickness is generally to beachieved through insert plates. Local doublers, which arenormally only allowed for temporary repair, may howeverbe accepted by the Society on a case-by-case basis.

In any case, doublers and insert plates are to be made ofmaterials of a quality at least equal to that of the plates onwhich they are welded.

2.3.2 Doublers having width, in mm, greater than:

• 20 times their thickness, for thicknesses equal to or lessthan 15 mm

• 25 times their thickness, for thicknesses greater than15 mm,

are to be fitted with slot welds, to be effected according toChapter 6.

2.3.3 When doublers fitted on the outer shell and strengthdeck within 0,6 L amidships are accepted by the Society,their width and thickness are to be such that slot welds arenot necessary according to the requirements in [2.3.2]. Out-side this area, the possibility of fitting doublers requiringslot welds will be considered by the Society on a case-by-case basis.


NR 600, Ch 2, Sec 1

2.4 Connections between steel and aluminium

2.4.1 Any direct contact between steel and aluminiumalloy is to be avoided.

Any heterogeneous jointing system is considered by theSociety on a case-by-case basis.

The use of transition joints made of aluminium/steel-cladplates or profiles is to be in accordance with NR216 Materi-als and Welding.

3 Bottom structure arrangement


3.1.1 The bottom structure is to be checked by theDesigner to make sure that it withstands the loads resultingfrom the dry-docking of the ship or the lifting by crane,when applicable. This check under such loading cases isnot within the scope of classification.

3.1.2 Provision is to be made for the free passage of waterfrom all the areas of the bottom to the suctions, by means ofscallops in floors and bottom girders.

3.1.3 Additional girder and floors may be fitted in theengine room to ensure adequate rigidity of the structure,according to the recommendations of the engine supplier.

3.1.4 If fitted, solid ballast is to be securely positioned. Ifnecessary, intermediate girders and floors may be required.The builder is to check that solid ballast material is compat-ible with the hull material.

3.1.5 Where face plates of floors and girders are at samelevel, the face plate of the stiffer member is generally to becontinuous. Butt welds of faces plates are to providestrength continuity.

3.1.6 As a rule, bottom girders are to be fitted in way ofeach line of pillars. If it is not the case, local longitudinalmembers are to be provided.

3.2 Longitudinal framing arrangement of single bottom

3.2.1 As a general rule, hull with a longitudinally framedsingle bottom is to be fitted with a continuous or inter-coastal centre girder welded to the floors.

3.2.2 Where side girders are fitted locally in lieu of centregirder, they are to be extended over a sufficient distancebeyond the ends of the centre girder and an additional stiff-ening of the bottom in the centreline area may be required.

3.2.3 Centre and side bottom girders are to be extended asfar as possible towards the ends of the hull.

3.2.4 Cut-outs fitted in web of floors for crossing of bottomlongitudinal are to be taken into account for the shear anal-ysis of floors.

3.3 Transverse framing arrangement of single bottom

3.3.1 Requirements of [3.1] apply also to transverse fram-ing in single bottom.

3.3.2 In general, the height, in m, of floors at the centrelineshould not be less than B/16. In the case of ship with con-siderable rise of floors, this height may be required to beincreased so as to ensure a satisfactory connection to theframes.

3.3.3 The ends of floors at side are to be aligned with sidetransverse members.

It may be accepted, on a case-by-case basis, that floor endsat side be welded on a primary longitudinal member of theside shell or the bottom.

3.3.4 Openings and cut-outs in the web of bottom girdersfor the crossing of floors are to be taken into account for thefloor shear analysis.

3.4 Double bottom arrangement

3.4.1 Double bottom heightAs a general rules, the double bottom height is to be:

• sufficient to ensure access to any part of the bottom, and

• not less than 0,76 m in way of the centre girder.

3.4.2 Where the height of the double bottom varies, thevariation is generally to be made gradually and over an ade-quate length.

The knuckles of inner bottom plating are to be located inway of floors.

Where such arrangements are not possible, suitable longitu-dinal structures such as partial girders, longitudinal bracketsetc., fitted across the knuckle, are to be fitted.

3.4.3 Adequate continuity is to be provided between dou-ble bottom area and single bottom area.

3.4.4 Floors are to be fitted:

• watertight in way of transverse watertight bulkheads

• reinforced in way of double bottom steps.

3.4.5 Where the double bottom height exceeds 0,9 m, webof floors and girders are to be strengthened by vertical stiff-eners spaced not more than 1 m apart.

These stiffeners may consist of:

• either bottom girders welded to the floors, or

• flat bars with, as a rule, a width equal to one tenth of thefloor depth and a thickness equal to the floors thickness.

3.4.6 Watertight floors are to be fitted with stiffeners havinga section modulus not less than that required for tank bulk-head vertical stiffeners.

3.4.7 In case of open floors consisting of a frame con-nected to the bottom plating and a reverse frame connectedto the inner bottom plating, the construction principle is tobe as shown on Fig 1.


NR 600, Ch 2, Sec 1

Figure 1 : Open floor

3.4.8 Double bottom compartment

Double bottom compartments are to be in accordance withSec 2, [4].

3.4.9 Duct keel

Where a duct keel is arranged, the continuity of the struc-ture of the floors is to be ensured.

3.5 Arrangement, scantlings and connections of bilge keels

3.5.1 Arrangement

Bilge keels may not be welded directly on the shell plating.An intermediate flat, or doubler, is required on the shellplating.

The thickness of the intermediate flat is to be equal to that ofthe bilge strake.

The ends of the bilge keels are to be sniped at an angle of15° or rounded with large radius. They are to be located inway of a transverse bilge stiffener. The ends of the interme-diate flat are to be sniped at an angle of 15°.

The arrangement shown in Fig 2 is recommended.

The arrangement shown in Fig 3 may also be accepted.

Figure 2 : Bilge keel arrangement

Figure 3 : Bilge keel arrangement

3.5.2 Materials

The bilge keel and the intermediate flat are to be made ofsteel with the same yield stress and grade as that of the bilgestrake.

3.5.3 Welding

Welding of bilge keel with intermediate plate connectionsis to be in accordance with Ch 6, Sec 2.

4 Side structure arrangement

4.1 General

4.1.1 In a transverse framing system, structure of sides ismade of secondary transverse frames, possibly supported byhorizontal stringers.

4.1.2 In a longitudinal framing system, structure of sidesare made of secondary longitudinal stiffeners supported byvertical primary supporting members.

4.1.3 Where the connection between side shell and deckplate is rounded, the radius, in mm, is to be not less than15 tS, where tS is the thickness, in mm, of the sheerstrake.

4.2 Stiffener arrangement

4.2.1 In general, the section modulus of ‘tweendeck framesis to be not less than that required for frames located imme-diately above.

4.2.2 Transverse web frames and secondary side frames areto be attached to floors and deck beams by brackets or anyother equivalent structure (see Ch 4, Sec 6).

4.2.3 For transverse framing system, the attention of theDesigner is drawn on the risk of buckling of side shell platepanels in way of ends of frames. Extra-thickness or addi-tional intercostal stiffeners may be requested in these areason the side shell.

shell plating


NR 600, Ch 2, Sec 1

4.3 Openings in the side shell plating

4.3.1 Openings in side shells are to be well rounded at thecorners and located, as far as practicable, well clear ofsuperstructure ends.

4.3.2 Large size openings are to be adequately compen-sated by means of insert plates of increased thickness. Suchcompensation is to be partial or total, depending on thestresses occurring in the area of the openings.

4.3.3 Secondary stiffeners cut in way of openings are to beattached to local structural members supported by the con-tinuous adjacent secondary stiffeners, or any other equiva-lent arrangement.

4.3.4 The sea chest thickness is generally to be equal tothat of the local shell plating

4.3.5 Openings for stabilizer fins are considered by theSociety on a case-by-case basis.

5 Deck structure arrangement

5.1 General

5.1.1 Adequate continuity of decks (plates and stiffeners) isto be ensured in way of:

• stepped strength decks

• changes in the framing system

• large openings.

5.1.2 Deck supporting structures under cranes and wind-lass are to be adequately stiffened.

5.1.3 Pillars or other supporting structures are generally tobe fitted under heavy concentrated loads on decks.

5.1.4 Stiffeners are also to be fitted in way of the ends andcorners of deck houses and partial superstructures.

5.1.5 Beams fitted at side of a deck hatch are to be effec-tively supported by at least two deck girders located at eachside of the deck opening.

5.2 Opening arrangement

5.2.1 The deck openings are to be as much spaced apart aspossible.

As practicable, they are to be located as far as possible fromthe highly stressed deck areas or from the stepped deckareas.

5.2.2 Extra thickness or additional reinforcements may berequested where deck openings are located:

• close to the primary transverse cross structure of plat-form of multihull

• in areas of deck structural singularity (cockpit, steppeddeck...)

• in way of the fixing of out-fittings.

5.2.3 As a rule, all the deck openings are to be fitted withradius corners. Generally, the corner radius is not to be lessthan 5% of the transverse width of the opening.

5.2.4 Corner radiusing, in the case of two or more openingsathwart ship in one single transverse section, is consideredby the Society on a case-by-case basis.

5.3 Hatch supporting structure

5.3.1 Hatch side girders and hatch end beams of reinforcedscantling are to be fitted in way of cargo hold openings.

In general, hatched end beams and deck transverses are tobe in line with bottom and side transverse structures, so asto form a reinforced ring.

Adequate continuity of strength of longitudinal hatch coam-ings is to be ensured.

The details of connection of deck transverses to longitudinalgirders and web frames are to be submitted to the Societyfor approval.

5.4 Pillars arrangement under deck

5.4.1 Pillars are to be connected to the inner bottom at theintersection of girders and floors and at deck at the intersec-tion of deck beams and deck girders.

Where it is not the case, an appropriate local partial struc-ture is to be fitted to support the pillars.

5.4.2 Pillars are to be attached at their heads and heels bycontinuous welding.

Heads and heels of pillars are to be attached to the sur-rounding structure by means of brackets, insert plates ordoubling plates so that the loads are well distributed.

In general, the thickness of insert plate or doubling plates isto be not less than 1,5 times the thickness of the pillar.

5.4.3 If tensile stress is expected in the pillar, an insert plateis to be put in place of doubling plate and head and heelbrackets may be required.

5.4.4 In tanks and in spaces intended for products whichmay procure explosive gases, solid or open section pillarsare to be fitted.

5.4.5 Manholes may not be cut in the girders and floorsbelow the heels of pillars.

5.4.6 Tight or non-tight bulkheads may be considered as pil-lars, provided that their scantling comply with Ch 4, Sec 7.

5.4.7 The scantlings of pillars are to comply with therequirements of Ch 4, Sec 7.


NR 600, Ch 2, Sec 1

6 Bulkhead structure arrangement

6.1 General

6.1.1 Plane bulkheads may be horizontally or verticallystiffened.

Stiffening of horizontally framed bulkheads consists of hori-zontal secondary stiffeners supported by vertical primarysupporting members.

Stiffening of vertically framed bulkheads consists of verticalsecondary stiffeners which may be supported by horizontalstringers.

The structural continuity of the vertical and horizontal pri-mary supporting members with the surrounding supportinghull structures is to be carefully ensured.

6.1.2 As a general rule, transverse bulkheads are to be stiff-ened, in way of bottom and deck girders, by vertical stiffen-ers in line with these girders or by an equivalent system.

Where a deck girder is not continuous, the bulkhead verti-cal stiffener supporting the end of the deck girder is to bestrong enough to sustain the bending moment transmittedby the deck girder.

6.2 Watertight bulkheads

6.2.1 Crossing through watertight transverse bulkheads ofbottom, side shell or deck longitudinal stiffeners are toclosed by watertight collar plates.

6.2.2 Ends of stiffeners of watertight bulkheads are to bealigned with the hull structure members, and are to be fittedwith end brackets.

Where this arrangement is made impossible due to hulllines, any other solution may be accepted provided embed-ding of the bulkhead secondary stiffeners is satisfactorilyachieved.

6.2.3 The secondary stiffeners of watertight bulkheads inthe ‘tweendecks may be snipped at ends, provided theirscantling is increased accordingly.

6.2.4 Watertight doors

The thickness of watertight doors is to be not less than theadjacent bulkhead plating, taking into account their actualspacing.

Where bulkhead stiffeners are cut in way of watertight door,reinforced stiffeners are to be fitted and suitably overlapped;cross-bars are to be provided to support the interrupted stiff-eners.

6.3 Non-tight bulkheads

6.3.1 As a rule, non-tight bulkheads not acting as pillars areto be provided with vertical stiffeners with a maximumspacing equal to:

• 0,9 m, for transverse bulkheads

• two-frame spacings, with a maximum of 1,5 m, for lon-gitudinal bulkheads.

6.3.2 Swash bulkheadsAs a rule, the total area of openings in swash bulkheads fit-ted in tanks is to be between 10% and 30% of the total areaof the swash bulkhead.

6.4 Corrugated bulkheads

6.4.1 GeneralThe main dimensions a, b, c and d of corrugated bulkheadsare defined in Fig 4.

Unless otherwise specified, the following requirement is tobe complied with:

Moreover, in some cases, the Society may prescribe anupper limit for the ratio b/t.

In general, the bending internal radius is to be not less thanthe following values, in mm:• for normal strength steel:

Ri = 2,5 t

• for high tensile steel:Ri = 3,0 t

When welds in a direction parallel to the bend axis are pro-vided in the zone of the bend, the welding procedures areto be submitted to the Society for approval, as a function ofthe importance of the structural element.

In general, where girders or vertical primary supportingmembers are fitted on corrugated bulkheads, they are to bearranged symmetrically.

Figure 4 : Corrugated bulkhead

6.4.2 Structural arrangementThe strength continuity of corrugated bulkheads is to beensured at ends of corrugations.

Where corrugated bulkheads are cut in way of primarymembers, attention is to be paid to ensure correct align-ment of corrugations on each side of the primary member.

The connection of the corrugated bulkhead with the deckand the bottom is to be carefully designed and speciallyconsidered by the Society.

In general, where vertically corrugated transverse bulkheadsare welded on the inner bottom:• plate floors are to be fitted in way of the flanges of cor-

rugations, and• girders are to be fitted in way of the flanges of corruga-

tions.

However, other arrangements ensuring adequate structuralcontinuity may be accepted by the Society.

a 1 2, d≤

b

c

d

a

t


NR 600, Ch 2, Sec 1

In general, the upper and lower parts of horizontally corru-gated bulkheads are to be flat over a depth equal to 0,1 D.

Where stools are fitted at the lower part of transverse bulk-heads, the thickness of adjacent plate floors is to be not lessthan that of the stool plating.

6.4.3 Bulkhead stool

In general, plate diaphragms or web frames are to be fittedin bottom stools in way of the double bottom longitudinalgirders or plate floors, as the case may be.

Brackets or deep webs are to be fitted to connect the upperstool to the deck transverses or hatch end beams, as thecase may be.

The continuity of the corrugated bulkhead with the stoolplating is to be adequately ensured. In particular, the upperstrake of the lower stool is to be of the same thickness andyield stress as those of the lower strake of the bulkhead.

6.5 Bulkhead acting as pillars

6.5.1 As a rule, bulkheads acting as pillars (i.e. those thatare designed to sustain the loads transmitted by a deckstructure) are to be provided with vertical stiffeners being, ata maximum two frames apart.

6.5.2 A Vertical stiffening member is to be fitted on thebulkhead in line with the deck supporting member transfer-ring the loads from the deck and is to be checked as definedin Ch 4, Sec 7.

6.6 Bracketed stiffeners

6.6.1 The bracket scantlings at ends of bulkhead stiffenersare carried out by direct calculation, taking into account thebending moment and shear forces acting on the stiffener inway of the bracket as defined in Ch 4, Sec 6.

7 Superstructures and deckhouses structure arrangement

7.1 Connection of superstructures and deckhouses with the hull structure

7.1.1 Superstructure and deckhouse frames are to be fitted,as far as practicable, in way of deck structure and are to beefficiently connected.

Ends of superstructures and deckhouses are to be efficientlysupported by bulkheads, diaphragms, webs or pillars.

Where hatchways are fitted close to the ends of superstruc-tures, additional strengthening may be required.

7.1.2 Construction details

The vertical stiffeners of the superstructure and deckhousewalls of the first tier (directly located above the freeboarddeck) are to be attached to the deck at their ends.

Brackets are to be fitted at the lower and, preferably too, atthe upper end of the vertical stiffeners of exposed frontbulkheads of engine casings and superstructures.

7.1.3 Connection to the hull deck of corners of superstruc-tures and deckhouses is considered by the Society on acase-by-case basis. Where necessary, local reinforcementsmay be required.

7.1.4 As a general rules, the side plating at ends of super-structures is to be tapered into the side shell bulwark or thesheerstrake of the strength deck.

Where a raised deck is fitted, the local reinforcement in wayof the step is to extend, as a general rules, over at least 3frame spacings.

7.2 Structural arrangement of superstructures and deckhouses

7.2.1 Web frames, transverse partial bulkheads or otherequivalent strengthening of each superstructure tier are tobe arranged, where practicable, in line with the transversereinforced structure below.

Web frames are also to be arranged in way of large open-ings, tender davits, winches, provision cranes and otherareas subjected to local loads.

Web frames, pillars, partial bulkheads and similar strength-ening are to be arranged, in conjunction with deck trans-verses, at ends of superstructures and deckhouses.

7.2.2 Openings

All the openings in superstructure and deckhouses exposedto greenseas are to be fitted with sills or coamings asdefined in Ch 5, Sec 1.

The attention of the Shipowners, Shipyards and Designer isdrawn on the fact that the Flag Administration may requestapplication of National Rules.

7.2.3 Access and doors

Access openings cut in sides plating of enclosed superstruc-tures are to be fitted with doors having a strength equivalentto the strength of the surrounding structure.

Special consideration is to be given to the connection ofdoors to the surrounding structure.

Securing devices which ensure watertightness are toinclude tight gaskets, clamping dogs or other similar appli-ances, and are to be permanently attached to the bulkheadsand doors. These doors are to be operable from both sides.

7.3 Strengthening of deckhouse in way of tenders and liferafts

7.3.1 Attention is drawn on any possible specific require-ments that could be issued by Flag Administration withrespect to local structure reinforcement in way of tendersand liferafts.


NR 600, Ch 2, Sec 2

SECTION 2 SUBDIVISION, COMPARTMENT ARRANGEMENT AND ARRANGEMENT OF HULL OPENINGS

Symbols

LLL : Load line length, in m, as defined in [2.1]FPLL : “Forward freeboard perpendicular”, to be taken

at the forward end of LLL and is to coincide withthe foreside of the stem on the waterline onwhich the length LLL is measured.

1 General

1.1 Application

1.1.1 The present Section is applicable to cargo ships ofless than 65 m in length and to non-cargo ships of less than90 m as defined in Ch 1, Sec 1, [1.1.2] in accordance withthe scope of application defined in Tab 1.

Table 1 : Scope of application

1.1.2 Additional specific arrangementsAdditional specific arrangement in relation to the servicenotation of the ship are defined in Ch 5, Sec 4.

1.1.3 Openings in superstructures and deck housesArrangement of openings in superstructures and deck-houses are defined in Ch 5, Sec 1.

2 Definition

2.1 Load line length

2.1.1 The load line length LLL is the distance, in m, on thewaterline at 85% of the least moulded depth from the top ofthe keel, measured from the forward side of the stem to thecentre of the rudder stock. LLL is to be not less than 96% of

the total length on the same waterline.

In ship design with a rake of keel, the waterline on whichthis length is measured is parallel to the designed waterlineat 85% of the least moulded depth Dmin found by drawing aline parallel to the keel line of the ship (including skeg) tan-gent to the moulded sheer line of the freeboard deck.Theleast moulded depth is the vertical distance measured fromthe top of the keel to the top of the freeboard deck beam atside at the point of tangency (see Fig 1).

Figure 1 : LLL of ships with a rake of keel

2.2 Machinery spaces of category A

2.2.1 Machinery spaces of category A are those spaces ortrunks to such spaces which contain:

• internal combustion machinery used for main propul-sion, or

• internal combustion machinery used for purposes otherthan propulsion where such machinery has in the aggre-gate a total power output of not less than 375 kW, or

• any oil fired boiler or fuel oil unit.

3 Subdivision arrangement

3.1 Number of transverse watertight bulkheads

3.1.1 General

All ships, in addition to complying with the requirements of[3.1.2], are to have at least the following transverse water-tight bulkheads:

• one collision bulkhead

• one after peak bulkhead for ships having the servicenotation passenger ship or ro-ro passenger ship

• two bulkheads forming the boundaries of the machineryspace in ships with machinery amidships, and a bulk-head forward of the machinery space in ships withmachinery aft. In the case of ships with an electrical pro-pulsion plant, both the generator room and the engineroom are to be enclosed by watertight bulkheads.

Gross tonnage < 500 GT (1) ≥ 500 GT (2)

Subdivision arrangement NR566 [3]

Compartment arrangement NR566 [4]

Access arrangement NR566 [5]

Arrangement of hull opening NR566 NR467

(1) Except ships having one of the following service nota-tions:• passenger ship with unrestricted navigation• ro-ro passenger ship with unrestricted navigation• fishing vessel• chemical tanker

(2) And ships having one of the service notations definedin (1), whatever their tonnage.

� ��

��

� ��

��


NR 600, Ch 2, Sec 2

3.1.2 Additional bulkheads

Additional bulkheads may be required for ships having tocomply with subdivision or damage stability criteria.

3.2 Water ingress detection

3.2.1 General

When a ship is fitted, below the freeboard deck, with singlecargo hold or cargo holds which are not separated by atleast one bulkhead made watertight up to the freeboarddeck, water ingress detection system is to be fitted accord-ing to NR467 Steel Ships, Pt C, Ch 1, Sec 10, [6.12.2].

3.2.2 Bulk carriers

For ships granted with the service notation bulk carrier,bulk carrier ESP, ore carrier ESP, combination car-rier/OBO ESP or combination carrier/OOC ESP, wateringress detection system is to be fitted according to NR467Steel Ships, Pt C, Ch 1, Sec 10, [6.12.1].

3.3 Collision bulkhead

3.3.1 A collision bulkhead is to be fitted which is to bewatertight up to the bulkhead deck. This bulkhead is to belocated at a distance from the forward perpendicular FPLL ofnot less than 5 per cent of the length LLL of the ship and,except as may be permitted by the Society, not more than 8per cent of LLL or 5 per cent of the LLL + 3 m, whichever isthe greater.

Note 1: For ships not covered by the SOLAS Convention, the lengthLLL need not be taken less than 50 m, unless required by theNational Authorities

3.3.2 Where any part of the ship below the waterlineextends forward of the forward perpendicular, e.g. a bul-bous bow, the distances, in metres, stipulated in [3.3.1] areto be measured from a point either:

• at the mid-length of such extension, or

• at a distance 1,5 per cent of the length LLL of the shipforward of the forward perpendicular.

3.3.3 The bulkhead may have steps or recesses providedthey are within the limits prescribed in [3.3.1] or [3.3.2].

No door, manhole, ventilation duct or any other opening is tobe fitted in the collision bulkhead below the bulkhead deck.

3.3.4 At Owner request and subject to the agreement of theflag Administration, the Society may, on a case-by-casebasis, accept a distance from the collision bulkhead to theforward perpendicular FP greater than the maximum speci-fied in [3.3.1] and [3.3.2], provided that subdivision andstability calculations show that, when the ship is in uprightcondition on full load summer waterline, flooding of thespace forward of the collision bulkhead will not result inany part of the freeboard deck becoming submerged, or inany unacceptable loss of stability.

In such a case, the attention of the Owner and the Shipyardis drawn to the fact that the flag Administration may imposeadditional requirements and that such an arrangement is, inprinciple, officialized by the issuance of a certificate ofexemption under the SOLAS Convention provisions. More-over, in case of change of flag, the taking Administrationmay not accept the exemption.

3.3.5 Where a long forward superstructure is fitted, the col-lision bulkhead is to be extended weathertight to the nextdeck above the bulkhead deck. The extension need not befitted directly above the bulkhead below provided it islocated within the limits prescribed in [3.3.1] or [3.3.2]with the exemption permitted by [3.3.6] and the part of thedeck which forms the step is made effectively weathertight.

3.3.6 Where bow doors are fitted and a sloping loadingramp forms part of the extension of the collision bulkheadabove the freeboard deck, the part of the ramp which ismore than 2,3 m above the freeboard deck may extend for-ward of the limit specified in [3.3.1] or [3.3.2]. The ramp isto be weathertight over its complete length.

3.3.7 The number of openings in the extension of the colli-sion bulkhead above the freeboard deck is to be restrictedto the minimum compatible with the design and normaloperation of the ship. All such openings are to be capable ofbeing closed weathertight.

3.4 After peak, machinery space bulkheads and stern tubes

3.4.1 GeneralBulkheads are to be fitted separating the machinery spacefrom the cargo and accommodation spaces forward and aftand made watertight up to the bulkhead deck. In passengerships, an after peak bulkhead is also to be fitted and madewatertight up to the bulkhead deck. The after peak bulkheadmay, however, be stepped below the bulkhead deck, pro-vided the degree of safety of the ship as regards subdivisionis not thereby diminished.

3.4.2 Sterntubes In all cases, sterntubes are to be enclosed in watertightspaces of moderate volume. In passenger ships, the sterngland is to be situated in a watertight shaft tunnel or otherwatertight space separate from the sterntube compartmentand of such volume that, if flooded by leakage through thestern gland, the bulkhead deck will not be immersed. Incargo ships, other measures to minimise the danger of waterpenetrating into the ship in case of damage to sterntubearrangements may be taken at the discretion of the Society.

3.5 Height of transverse watertight bulkheads other than collision bulkhead and after peak bulkheads

3.5.1 Transverse watertight bulkheads are to extend water-tight up to the bulkhead deck. In exceptional cases at therequest of the Owner, the Society may allow transversewatertight bulkheads to terminate at a deck below that fromwhich freeboard is measured, provided that this deck is atan adequate distance above the full load waterline.


NR 600, Ch 2, Sec 2

3.5.2 Where it is not practicable to arrange a watertightbulkhead in one plane, a stepped bulkhead may be fitted. Inthis case, the part of the deck which forms the step is to bewatertight and equivalent in strength to the bulkhead.

3.6 Openings in watertight bulkheads and decks for ships with service notation other than passenger ship or ro-ro passenger ship

3.6.1 The requirements from [3.6.2] to [3.6.10] apply toships with service notation other than passenger ship or ro-ro passenger ship.

The requirements for openings in watertight bulkheadsbelow the bulkhead deck in ships with service notation pas-senger ship and ro-ro passenger ship are to comply withNR467 Steel Ships, Part D, Chapter 11 and Chapter 12respectively.

3.6.2 The number of openings in watertight subdivisions isto be kept to a minimum compatible with the design andproper working of the ship. Where penetrations of water-tight bulkheads and internal decks are necessary for access,piping, ventilation, electrical cables, etc., arrangement is tobe made to maintain the watertight integrity. The Societymay permit relaxation in the watertightness of openingsabove the freeboard deck, provided that it is demonstratedthat any progressive flooding can be easily controlled andthat the safety of the ship is not impaired.

3.6.3 No door, manhole ventilation duct or any otheropening is permitted in the collision bulkhead below thesubdivision deck.

3.6.4 Lead or other heat sensitive materials may not be usedin systems which penetrate watertight subdivision bulk-heads, where deterioration of such systems in the event offire would impair the watertight integrity of the bulkheads.

3.6.5 Valves not forming part of a piping system are notpermitted in watertight subdivision bulkheads.

3.6.6 The requirements relevant to the degree of tightness,as well as the operating systems, for doors or other closingappliances complying with the provisions from [3.6.7] to[3.6.10] are specified in Tab 2.

3.6.7 Openings used while at seaDoors provided to ensure the watertight integrity of internalopenings which are used while at sea are to be slidingwatertight doors capable of being remotely closed from thebridge and are also to be operable locally from each side ofthe bulkhead. Indicators are to be provided at the controlposition showing whether the doors are open or closed, andan audible alarm is to be provided at the door closure. Thepower, control and indicators are to be operable in theevent of main power failure. Particular attention is to bepaid to minimise the effect of control system failure. Eachpower-operated sliding watertight door is to be providedwith an individual hand-operated mechanism. The possibil-ity of opening and closing the door by hand at the dooritself from both sides is to be assured.

3.6.8 Openings normally closed at seaAccess doors and access hatch covers normally closed atsea, intended to ensure the watertight integrity of internalopenings, are to be provided with means of indicationlocally and on the bridge showing whether these doors orhatch covers are open or closed. A notice is to be affixed toeach such door or hatch cover to the effect that it is not tobe left open.

Table 2 : Doors

Sliding type Hinged type Rolling type

(cargo between

deck spaces)

Remote operation indication

on the bridge

Indicator on the bridge

Localoperation

only

Remote operation indication

on the bridge

Indicator on the bridge

Localoperation

only

Watertight Below the freeboard deck

Open at sea X

Normally closed (2)

X X

Remain closed (2)

X (3) (4) X (3) (4) X (3) (4)

Weathertight / watertight (1)

Above the freeboard deck

Open at sea X

Normally closed (2)

X X

Remain closed (2)

X (3) (4)

(1) Watertight doors are required when they are located below the waterline at the equilibrium of the final stage of flooding; other-wise a weathertight door is accepted.

(2) Notice to be affixed on both sides of the door: “to be kept closed at sea”.(3) The door is to be closed before the voyage commences.(4) If the door is accessible during the voyage, a device which prevents non authorised opening is to be fitted.


NR 600, Ch 2, Sec 2

3.6.9 Doors or ramps in large cargo spaces

Watertight doors or ramps of satisfactory construction maybe fitted to internally subdivide large cargo spaces, pro-vided that the Society is satisfied that such doors or rampsare essential. These doors or ramps may be hinged, rollingor sliding doors or ramps, but are not to be remotely con-trolled. Such doors are to be closed before the voyage com-mences and are to be kept closed during navigation. Shouldany of the doors or ramps be accessible during the voyage,they are to be fitted with a device which prevents nonauthorised opening.

The word “satisfactory” means that scantlings and sealingrequirements for such doors or ramps are to be sufficient towithstand the maximum head of the water at the floodedwaterline.

3.6.10 Openings permanently kept closed at sea

Other closing appliances which are kept permanentlyclosed at sea to ensure the watertight integrity of internalopenings are to be provided with a notice which is to beaffixed to each such closing appliance to the effect that it isto be kept closed. Manholes fitted with closely bolted cov-ers need not be so marked.

4 Compartment arrangement

4.1 Definitions

4.1.1 Cofferdam

A cofferdam means an empty space arranged so that com-partments on each side have no common boundary; a cof-ferdam may be located vertically or horizontally. As a rule,a cofferdam is to be properly ventilated and of sufficientsize to allow for inspection.

4.2 Cofferdam arrangement

4.2.1 Cofferdams are to be provided between:

• fuel oil tanks and lubricating oil tanks

• compartments intended for liquid hydrocarbons (fueloil, lubricating oil) and compartments intended for freshwater (drinking water, water for propelling machineryand boilers)

• compartments intended for liquid hydrocarbons (fueloil, lubricating oil) and tanks intended for the carriage ofliquid foam for fire extinguishing.

4.2.2 Cofferdams separating:

• fuel oil tanks from lubricating oil tanks

• lubricating oil tanks from compartments intended forfresh water or boiler feed water

• lubricating oil tanks from those intended for the carriageof liquid foam for fire extinguishing,

may not be required when deemed impracticable or unrea-sonable by the Society in relation to the characteristics anddimensions of the spaces containing such tanks, providedthat:

• the thickness of common boundary plates of adjacenttanks is increased, with respect to the thicknessobtained according to Ch 4, Sec 3, by 2 mm in the caseof tanks carrying fresh water or boiler feed water, and by1 mm in all other cases

• the sum of the throats of the weld fillets at the edges ofthese plates is not less than the thickness of the platesthemselves

• the structural test is carried out with a head increased by1 m with respect to Ch 6, Sec 3.

4.2.3 Spaces intended for the carriage of flammable liquidsare to be separated from accommodation and servicespaces by means of a cofferdam. Where accommodationand service spaces are arranged immediately above suchspaces, the cofferdam may be omitted only where the deckis not provided with access openings and is coated with alayer of material recognized as suitable by the Society.

The cofferdam may also be omitted where such spaces areadjacent to a passageway, subject to the conditions stated in[4.2.2] for fuel oil or lubricating oil tanks.

4.3 Double bottom

4.3.1 Excepting ships having the service notation fishingvessel, a double bottom is to be fitted extending from thecollision bulkhead to the after peak bulkhead, as far as thisis practicable and compatible with the design and properworking of the ship.

4.3.2 Any part of a ship that is not fitted with a double bot-tom is to be capable of withstanding bottom damages asspecified in NR467 Steel Ships, Pt B, Ch 3, Sec 3 [3.4].

4.3.3 Where a double bottom is required to be fitted, theinner bottom is to be continued out to the ship’s sides insuch a manner as to protect the bottom to the turn of thebilge. Such protection is to be deemed satisfactory if theinner bottom is not lower at any part than a plane parallelwith the keel line and which is located not less than a verti-cal distance h measured from the keel line, as calculated bythe formula:

h = B / 20

However, in no case is the value of h to be less than760 mm, and need not to be taken as more than 2 m.

4.3.4 Small wells constructed in the double bottom, in con-nection with the drainage arrangements of holds, are not toextend downward more than necessary. A well extending tothe outer bottom, is, however, permitted at the after end ofthe shaft tunnel of the ship. Other wells may be permittedby the Society if it is satisfied that the arrangements giveprotection equivalent to that afforded by a double bottomcomplying with [4.3]. In no case, the vertical distance fromthe bottom of such a well to a plane coinciding with thekeel line is to be less than 500 mm.

4.3.5 Additional requirements for passenger ship and tankers

Special requirements for passenger ships and tankers arespecified in NR467 Steel Ships, Part D, Ch 12, Sec 2.


NR 600, Ch 2, Sec 2

4.3.6 Additional requirements for oil tankers

Double bottom requirements for oil tankers with regard tofire prevention and pollution prevent on are defined inNR467 Steel ships, Part D, Ch 7, Sec 2.

4.4 Compartments forward of the collision bulkhead

4.4.1 The fore peak and other compartments located for-ward of the collision bulkhead cannot be used for the car-riage of fuel or other flammable products.

4.5 Minimum bow height

4.5.1 The minimum bow height Fb is to be as defined inNR566, Ch 1, Sec 4 [12].

4.6 Shaft tunnels

4.6.1 Shaft tunnels are to be watertight.

4.7 Watertight ventilators and trunks

4.7.1 Watertight ventilators and trunks are to be carried atleast up to:

• the freeboard deck in ships other than passenger ships

• the bulkhead deck in passenger ships.

4.8 Fuel oil tanks

4.8.1 The arrangements for the storage, distribution and uti-lisation of the fuel oil are to be such as to ensure the safetyof the ship and persons on board.

4.8.2 As far as practicable, fuel oil tanks are to be part ofthe ship’s structure and are to be located outside machineryspaces of category A.

Where fuel oil tanks, other than double bottom tanks, arenecessarily located adjacent to or within machinery spacesof category A, at least one of their vertical sides is to be con-tiguous to the machinery space boundaries, they are prefer-ably to have a common boundary with the double bottomtanks and the area of the tank boundary common with themachinery spaces is to be kept to a minimum.

Where such tanks are situated within the boundaries ofmachinery spaces of category A, they may not contain fueloil having a flashpoint of less than 60°C.

4.8.3 Fuel oil tanks may not be located where spillage orleakage therefrom can constitute a hazard by falling onheated surfaces.

Precautions are to be taken to prevent any oil that mayescape under pressure from any pump, filter or heater fromcoming into contact with heated surfaces.

Fuel oil tanks in boiler spaces may not be located immedi-ately above the boilers or in areas subjected to high temper-atures, unless special arrangements are provided inagreement with the Society.

4.8.4 Where a compartment intended for goods or coal issituated in proximity of a heated liquid container, suitablethermal insulation is to be provided.

4.8.5 Fuel oil tank protection

All ships with an aggregate oil fuel capacity of 600 m3 areto comply with the requirements of the Regulation 12 A ofAnnex I to Marpol Convention, as amended.

5 Access arrangement

5.1 General

5.1.1 The number and size of small hatchways for trimmingand access openings to tanks or other enclosed spaces, areto be kept to the minimum consistent with access and main-tenance of the space.

5.2 Double bottom

5.2.1 Manholes are to be provided in floors and girders soas to provide convenient access to all parts of the doublebottom.

5.2.2 Manholes may not be cut into the continuous cen-treline girder or floors and girders below pillars, exceptwhere allowed by the Society on a case-by-case basis.

5.2.3 Inner bottom manholes are to be not less than400 mm x 400 mm. Their number and location are to be soarranged as to provide convenient access to any part of thedouble bottom.

5.2.4 However, the size of manholes and lightening holesin floors and girders is, in general, to be less than 50 percent of the local height of the double bottom.

Where manholes of greater sizes are needed, edge rein-forcement by means of flat bar rings or other suitable stiffen-ers may be required.

5.2.5 Inner bottom manholes are to be closed by watertightplate covers.

Doubling plates are to be fitted on the covers, wheresecured by bolts.

Where no ceiling is fitted, covers are to be adequately pro-tected from damage by the cargo.

5.3 Access arrangement to and within spaces in, and forward of, the cargo area

5.3.1 General

The requirement defined for access to tank (see [5.3.2]),access within tanks (see [5.3.3]) and construction of ladders(see [5.3.4]) are not applicable to:

• ships with service notation oil tanker ESP (see NR467Steel Ships, Part D, Chapter 7)

• spaces in double bottom and double side tanks.


NR 600, Ch 2, Sec 2

Specific additional requirements, defined in NR467 SteelShips, Part D, are applicable to the following service notations:

- livestock carrier: see NR467, Part D, Chapter 3

- bulk carrier: see NR467, Part D, Chapter 4

- ore carrier: see NR467, Part D, Chapter 5

- combination carrier: see NR467, Part D, Chapter 6

- oil tanker: see NR467, Part D, Chapter 7

- chemical tanker: see NR467, Part D, Chapter 8

- ro-ro passenger ship: see NR467, Part D, Chapter 12.

5.3.2 Access to tanksTanks and subdivisions of tanks having lengths of 35 m andabove are to be fitted with at least two access hatchwaysand ladders, as far apart as practicable longitudinally.

Tanks less than 35 m in length are to be served by at leastone access hatchway and ladder.

The dimensions of any access hatchway are to be sufficientto allow a person wearing a self-contained breathing appa-ratus to ascend or descend the ladder without obstructionand also to provide a clear opening to facilitate the hoistingof an injured person from the bottom of the tank. In no caseis the clear opening to be less than 600 mm x 600 mm.

When a tank is subdivided by one or more swash bulk-heads, at least two hatchways are to be fitted, and thesehatchways are to be so located that the associated ladderseffectively serve all subdivisions of the tank.

5.3.3 Access within tanksWhere one or more swash bulkheads are fitted in a tank,they are to be provided with openings not less than600 x 800 mm and so arranged as to facilitate the access ofpersons wearing breathing apparatus or carrying a stretcherwith a patient.

To provide ease of movement on the tank bottom through-out the length and breadth of the tank, a passageway is tobe fitted on the upper part of the bottom structure of eachtank, or alternatively, manholes having at least the dimen-sions of 600 mm x 800 mm are to be arranged in the floorsat a height of not more than 600 mm from the bottom shellplating.

Passage way in the tank:

a) Passageways in the tanks are to have a minimum widthof 600 mm considering the requirement for the possibil-ity of carrying an unconscious person. Elevated passage-ways are to be provided with guard rails over their entirelength. Where guard rails are provided on one side only,foot rails are to be fitted on the opposite side. Shelvesand platforms forming a part of the access to the tanksare to be of non-skid construction where practicableand be fitted with guard rails. Guard rails are to be fittedto bulkhead and side stringers when such structures arebeing used for recognised access.

b) Access to elevated passageways from the ship's bottomis to be provided by means of easily accessible passage-ways, ladders or treads. Treads are to provide lateralsupport for the foot. Where rungs of ladders are fittedagainst a vertical surface, the distance from the centre ofthe rungs to that surface is to be at least 150 mm.

c) When the height of the bottom structure does notexceed 1,50 m, the passageways required in a) may bereplaced by alternative arrangements having regard tothe bottom structure and requirement for ease of accessof a person wearing a self-contained breathing appara-tus or carrying a stretcher with a patient.

Where manholes are fitted, as indicated in [5.2.4], access isto be facilitated by means of steps and hand grips with plat-form landings on each side.

Guard rails are to be 900 mm in height and consist of a railand intermediate bar. These guard rails are to be of substan-tial construction.

5.3.4 Construction of laddersIn general, the ladders are not to be inclined at an angleexceeding 70°. The flights of ladders are not to be morethan 9 m in actual length. Resting platforms of adequatedimensions are to be provided.

Ladders and handrails are to be constructed of steel of ade-quate strength and stiffness and securely attached to thetank structure by stays. The method of support and length ofstay are to be such that vibration is reduced to a practicalminimum.

Provision is to be made for maintaining the structuralstrength of the ladders and railings taking into account thecorrosive effect of the cargo.

The width of ladders between stringers is not to be less than400 mm.

The treads are to be equally spaced at a distance apartmeasured vertically not exceeding 300 mm. They are to beformed of two square steel bars of not less than 22 mm by22 mm in section fitted to form a horizontal step with theedges pointing upward, or of equivalent construction. Thetreads are to be carried through the side stringers andattached thereto by double continuous welding.

All sloping ladders are to be provided with handrails of sub-stantial construction on both sides fitted at a convenient dis-tance above the treads.

5.4 Shaft tunnels

5.4.1 Tunnels are to be large enough to ensure easy accessto shafting.

5.4.2 Access to the tunnel is to be provided by a watertightdoor fitted on the aft bulkhead of the engine room in com-pliance with [3.6], and an escape trunk which can also actas watertight ventilator is to be fitted up to the subdivisiondeck, for tunnels greater than 7 m in length.

5.5 Access to steering gear compartment

5.5.1 The steering gear compartment is to be readily acces-sible and, as far as practicable, separated from machineryspaces.

Suitable arrangements to ensure working access to steeringgear machinery and controls are to be provided.

These arrangements are to include handrails and gratings orother non-slip surfaces to ensure suitable working condi-tions in the event of hydraulic fluid leakage.


NR 600, Ch 2, Sec 3

SECTION 3 SCANTLING CRITERIA

Symbols

R : Minimum yield stress value as defined in[2.1.1].

σVM : Von Mises equivalent stress, in N/mm2 obtainedfrom the following formula:

1 General

1.1 Application

1.1.1 The requirements of the present Section define:

• the permissible stresses considered for the check of steeland aluminium structures

• the safety factors considered for the check of compositestructures.

1.2 Global and local stress

1.2.1 General

As a rule, the global hull girder strength and the localstrength are examined independently (see also Ch 1, Sec 3,[2]).

1.3 Stress notation

1.3.1 As a rule, the notations used for the stresses are:

σ : Bending, compression or tensile stress

τ : Shear stress.

The following indexes are used depending on the type ofstress considered:

am : Rule permissible stress values

gl : Stresses resulting from global strength analysisas defined in Ch 4, Sec 2

loc : Stresses resulting from local strength analysis asdefined from Ch 4, Sec 3 to Ch 4, Sec 5

VM : Combined stress calculated according to VonMises criteria.

2 Steel and aluminium alloy structures

2.1 Permissible stresses for structure

2.1.1 Permissible stresses for plates and secondary stiffeners

The permissible stresses for plating and secondary stiffenersare based on the minimum yield stress value R, in N/mm2,and are defined in Tab 1.

R is to be taken equal to:

• for steel structures: the minimum yield stress value Ry asdefined in Ch 1, Sec 2, [2.1.5]

• for aluminium structures: the minimum yield stress R’limas defined in Ch 1, Sec 2, [3.1.3].

2.1.2 Permissible stresses for primary stiffeners

The permissible stresses for primary stiffeners are based onthe minimum yield stress value R (as defined in [2.1.1]) andon the type of beam model calculation carried out to checkthe primary structure.

a) For isolated beam model:

The permissible stresses are defined in Tab 2.

b) For two or three dimensional beam model:

It is to be checked that the equivalent stress σVM is incompliance with the following formula:

σVM ≤ 1,1 σVMam

where:

σVMam : Permissible equivalent stress defined in Tab 2.

c) For finite element model:

It is to be checked that the equivalent stress σVM is incompliance with the following formula:

σVM ≤ σMASTER

where:

σMASTER : Master allowable stress, in N/mm2, equal to1,1 σVMam

σVMam : Permissible equivalent stress defined in Tab 2.

In a fine mesh, where high stress are to be investigatedthrough a very fine mesh structural detail analysis, thecriteria to be checked are defined in NR467 Steel Ships,Pt B, Ch 7, Sec 3, taking into account the value ofσMASTER defined here above.

σVM σ2 3τ2+=


NR 600, Ch 2, Sec 3

Table 1 : Permissible stresses and safety factor for plating and secondary stiffeners in steel or aluminium materials

Table 2 : Permissible stresses for primary structure in steel or aluminium materials

Type of stress considered Type of element consideredDesign permissible stress,

in N/mm2

Global stress induced by longitudinal hull girderloads and by hull girder torque for multihull (1)

Platingσglam = 0,50 R (2)

τglam = 0,40 R

Stiffeners σglam = 0,50 R

Plating and stiffeners safety factor for buckling SF = 1,70

Local stress induced by external sea pressure andby internal loads

Plating σlocam = 0,65 R

Stiffenersσlocam = 0,65 R

τlocam = 0,45 R

Plating and stiffeners safety factor for buckling SF = 1,70

Local stress induced by external slamming loadson bottom or impact on flat bottom on forwardarea or by external impact pressure on side shells


Stiffeners: general case σlocam = 0,75 R

τlocam = 0,50 R

Stiffeners: flat bottom forward areaσlocam = 0,90 R

τlocam = 0,55 R

Local stress induced by exceptional damageloads or by tank testing loads


Stiffeners σlocam = 0,80 R

τlocam = 0,50 R

(1) The design permissible stresses may be increased from 30% and the safety factor for buckling may be decreased from 30% for:• high speed ship, when the global stress is calculated with the minimum bending moments defined in Ch 3, Sec 2, [6.1] • swath ship, when the global stress is calculated with the bending moment acting on twin-hull defined in Ch 3, Sec 2, [6.2.2].

(2) See Ch 1, Sec 3, [2].

Type of stress considered Type of element consideredDesign permissible stress,

in N/mm2

Local stress induced by external sea pressure and by internal loads

Primary structure contributing to the longitu-dinal strength (or transversal strength for multihull)

σlocam = 0,55 R

τlocam = 0,45 R

σVMam = 0,70 R

SF buckling = 1,70

Local stress induced by external slamming loads on bottom or by exceptional damage loads

σlocam = 0,70 R

τlocam = 0,50 R

σVMam = 0,80 R

Local stress induced by external sea pressure and by internal loads

Primary structure not contributing to the lon-gitudinal strength (or transversal strength for multihull)

σlocam = 0,70 R

τlocam = 0,50 R

σVMam = 0,85 R

SF buckling = 1,70

Local stress induced by external slamming loads on bottom, or impact on flat bottom on forward area or by exceptional damage loads

σlocam = 0,85 R

τlocam = 0,50 R

σVMam = 0,90 R


NR 600, Ch 2, Sec 3

3 Composite materials structure

3.1 General

3.1.1 Principle of design reviewThe design review of composites structures is based onsafety factors defined as the ratio between the appliedstresses (calculated on the basis of the present rules) and:• the theoretical breaking stresses of the elementary layers

of the full lay-up laminates (defined in NR546 Compos-ite Ships, Section 5), and

• the critical buckling of the whole laminate (defined inNR546 Composite Ships, Section 6).

These safety factors are to be greater than the rules safetyfactor values defined in [3.2].Note 1: Breaking stresses directly deduced from mechanical tests(as requested in NR546 Composite Ships), may be taken over fromtheoretical breaking stresses if mechanical test results are noticea-bly different from expected values.

3.1.2 Type of stress consideredThe following different type of stresses are considered, cor-responding to the different loading mode of the fibres:

a) Principal stresses in the individual layers:• Stress parallel to the fibre (longitudinal direction).

These stresses, σ1, may be tensile or compressivestresses, and are mostly located as follows:- in 0° direction of unidirectional tape or fabric

reinforcement systems- in 0° and 90° directions of woven roving

• Stress perpendicular to the fibre (transverse direc-tion). These stresses, σ2, may be tensile or compres-sive stresses, and are mostly located as follows:- in 90° direction of unidirectional tape or com-

bined fabrics when the set of fibres are stitchedtogether without criss-crossing

• Shear stress (in the laminate plane) parallel to thefibre. These shear stresses, τ12, may be found in alltype of reinforcement systems

• Shear stress (through the laminate thickness) parallelor perpendicular to the fibre. These shear stresses,τ13 and τ23, are the same stresses than the interlami-nar shear stresses τIL2 and τIL1

• Combined stress (Hoffman criteria)

b) Stresses in the whole laminate:• Compressive and shear stresses in the whole lami-

nate inducing buckling.

3.1.3 Theoretical breaking criteriaThree theoretical breaking criteria are used in the presentRules:

a) maximum stress criteria leading to the breaking of thecomponent resin/fibre of one elementary layer of the fulllay-up laminate (see [3.2.1])

b) Hoffman combined stress criteria with the hypothesis ofin-plane stresses in each layer (see [3.2.2])

c) critical buckling stress criteria applied to the laminate(see [3.2.3]).

The theoretical breaking criteria defined in a) and b) are tobe checked for each individual layer.

The theoretical breaking criteria defined in c) is to bechecked for the global laminate.

3.1.4 First ply failure

It is considered that the full lay-up laminate breakingstrength is reached as soon as the lowest breaking strengthof any elementary layer is reached. This is referred to as“first ply failure”.

3.2 Rules safety factors

3.2.1 Application to maximum stress criteria in layers

As a general rule, the rules safety factor SF applicable tomaximum stress considered in the present Rules is to be cal-culated as follows:

SF = CV CF CR CI

where:

CV : Coefficient taking into account the ageing effectof the composites. CV is generally taken equalto:

• 1,2 for monolithic laminates (or face-skinslaminates of sandwich)

• 1,1 for sandwich core materials

CF : Coefficient taking into account the fabricationprocess and the reproducibility of the fabrica-tion. CF is directly linked to the mechanicalcharacteristics to be considered during a com-posites hull construction and is generally takenequal to:

• 1,2 in case of a prepreg process

• 1,3 in case of infusion and vacuum process

• 1,4 in case of a hand lay up process

• 1,0 for the core materials of sandwich com-posite.

CR : Coefficient taking into account the type of stressin the fibres of the reinforcement fabric and thecore. CR is generally taken equal to:

• For fibres of the reinforcement fabrics:

- 2,6 for a tensile or compressive stressparallel to the continuous fibre of thereinforcement fabric (unidirectionaltape, bi-bias, three unidirectional fabric,woven roving)

- 1,2 for tensile or compressive stress per-pendicular to the continuous fibre of thereinforcement fabric (unidirectional tapebi-bias, three unidirectional fabric)

- 2,0 for a shear stress parallel to the fibrein the elementary layer and for interlam-inar shear stress in the laminate

- 2,0 whatever the type of stress in an ele-mentary layer of mat type


NR 600, Ch 2, Sec 3

• For core materials:

- 2,0 for a tensile or compressive stress forfoam core

- 2,6 for a tensile or compressive stressparallel to the wood grain for balsa core

- 1,2 for tensile or compressive stress per-pendicular to the wood grain for balsacore

- 2,5 for a shear stress (whatever the typeof core material)

• Wood materials for strip planking:

- Same values as defined in the first bulletlist, for unidirectional tape

CI : Coefficient taking into account the type ofloads. CI is generally taken equal to:

• 1,0 for hydrodynamic sea pressure and con-centrated forces

• 0,8 for slamming loads on bottom, impacton flat bottom on forward area, impact pres-sure on side shell and on platform bottom ofmultihull, test pressure or for exceptionaldamage loads.

Note 1: For high speed ship, when the global stress is calcu-lated with the minimum bending moments defined inCh 3, Sec 2, [6.1], CI may be taken equal to 0,8.

3.2.2 Combined stress criteria in layers

The Hoffman (or Tsaï Wu) combined stress criteria consid-ered in the present Rules is to be as defined in NR546 Com-posite Ships, Section 2.

As a general rule, the rules safety factor SFCS considered forthe combined stress in the present Rules is to be calculatedas follows:

a) General case:

SFCS = 1,8 CV CF Ci

b) Primary stiffeners checked by a two or three dimen-sional beam model or by a finite element calculation:

SFCS = 1,6 CV CF Ci

where:

CF, CV, Ci : Coefficients as defined in [3.2.1].

Note 1: For high speed ship, when the global stress is calculatedwith the minimum bending moments defined in Ch 3, Sec 2, [6.1],CI may be taken equal to 0,8.

3.2.3 Application to critical buckling stress criteria

As a general rule, the rules safety factor SFB considered inthe present Rules for critical buckling is to be calculated asfollows:

SFB = 1,6 CF CV

where:

CF, CV : Coefficients as defined in [3.2.1].

Note 1: For high speed ship, when the global stress is calculatedwith the minimum bending moments defined in Ch 3, Sec 2, [6.1],The safety factor SFB may be reduced from 20%.

3.2.4 Application to maximum stress criteria in structural adhesive joint

For structural adhesive joint, a maximum breaking shearstress from 5 N/mm2 to 10 N/mm2 (for high performancebonding) is usually considered.

Other values given by the manufacturer may be taken intoaccount, based on mechanical test results. In this case, testcontext must be similar to the bonding carried out on board(type of component to be bonded, process...).

As a general rule, the rules safety factor SF applicable tomaximum shear stress in adhesive joint considered in thepresent Rules is to be calculated as follows:

SF = 2,4 CF

where:

CF : Coefficient taking into account the gluing proc-ess, and generally taken equal to:

• 1,4 in case of a vacuum process with risingcuring temperature

• 1,5 in case of vacuum process

• 1,7 in the other cases.

3.3 Additional consideration on rules safety factor

3.3.1 Rules safety factors other than those defined in[3.2.1] and [3.2.2] may be accepted for one elementarylayer when the full lay-up laminate exhibits a sufficientsafety margin between the theoretical breaking of this ele-mentary layer and the theoretical breaking of the other ele-mentary layers.

4 Plywood structure

4.1 General

4.1.1 Principle of design review

As a rule, plywood structure are checked according to anhomogeneous material approach, or by a “ply by ply”approach as defined in NR546 Composite Ships.

4.2 Rules safety factor

4.2.1 Homogeneous material approach

As a general rule, the rules safety factor SF to take intoaccount in the global formula used to determined the thick-ness of plating or the permissible stress in stiffener is to be atleast greater than 4.

4.2.2 Ply by ply approach

As a general rule, the rules safety factor SF applicable to themaximum stress in each layer of the plywoods is to be cal-culated as follows:

SF = CR Ci CV

where:


NR 600, Ch 2, Sec 3

CR : Coefficient taking into account the type of stressin the grain of the layer of the plywood. CR isgenerally taken equal to:

• 3,7 for a tensile or compressive stress paral-lel to the grain of the ply considered

• 2,4 for tensile or compressive stress perpen-dicular to the grain of the ply considered

• 2,9 for a shear stress parallel to the grain ofthe ply considered

Ci : Coefficient taking into account the type ofloads. Ci is generally taken equal to:

• 1,0 for hydrodynamic sea pressure and con-centrated forces

• 0,8 for slamming loads on bottom, impacton flat bottom on forward area, impact pres-sure on side shell and on platform bottom ofmultihull, test pressure or for exceptionaldamage loads

CV : Coefficient taking into account the ageing effectof the plywood, to be taken at least equal to 1,2.


NR 600, Ch 2, Sec 3


NR 600

Chapter 3

DESIGN LOADS

SECTION 1 GENERAL

SECTION 2 HULL GIRDER LOADS

SECTION 3 LOCAL EXTERNAL PRESSURES

SECTION 4 LOCAL INTERNAL PRESSURE AND FORCES


NR 600, Ch 3, Sec 1

SECTION 1 GENERAL

1 Application

1.1 General

1.1.1 As a general rules, wave loads, ship motions and accel-erations defined in the present Chapter are assumed to beperiodic and can be reached with a probability level of 10-5.

1.1.2 As an alternative to the present chapter, the Societymay accept the values of ship motions and accelerationsderived from direct calculations or obtained from modeltests, when justified on the basis of the ship’s characteristicsand intended service. In general, the values of ship motionsand accelerations to be determined are those which can bereached with the probability level defined in [1.1.1]. In anycase, the model tests or the calculations, including theassumed sea scatter diagrams and spectra, are to be submit-ted to the Society for approval.

1.1.3 Requirements applicable to specific ship types

Additional specific loads of NR467 Steel Ships, Part D maybe considered in addition to those defined in the presentChapter in relation to the service notations or additionalservice features assigned to the ship (see Ch 5, Sec 4).

2 Definition


2.1.1 Hull girder loads (still water, wave and dynamics) areforces and moments which result as effects of local loadsacting on the ship as a whole and considered as a beam.

These loads are considered for the hull girder strength checkand are defined in Sec 2.

2.2 Local external pressures

2.2.1 The local external pressures are local pressures (stillwater, wave and dynamics) applied to the individual localstructure (plating, secondary stiffeners and primary support-ing members).

These local external pressures are considered for the localstructure check and are defined in Sec 3.

2.3 Local internal pressures and forces

2.3.1 The local internal pressures and forces are local pres-sures (still water and inertial pressure) applied to the localinternal structure (plating, secondary stiffeners and primarysupporting structure) and include liquid loads, dry cargoes(bulk, uniform or unit), wheeled loads and accommodationdeck loads.

Flooding pressures induced by damage, and testing pres-sure are also considered as local internal pressures.

These local internal pressures and forces are considered forthe local internal structure check and are defined in Sec 4.

3 Local pressure application

3.1 Application

3.1.1 The local pressures to be used in the scantling checksof plating, secondary stiffeners and primary supportingmembers are to be as follows:

a) Element of the outer shell:

The local external pressures (still water and wave) con-sidered as acting alone without any counteraction fromthe ship interior loads in ship full load condition

However, for element of the outer shell adjacent to aliquid compartment, the local load to be used in thescantling checks of plating, secondary stiffeners and pri-mary supporting members of the shell is to be takenequal to the greater value between:

• the local load as defined just above, and

•

where:

pint : Local internal pressure, in kN/m2, asdefined in Sec 4

TB : Draught, in m, in ballast conditionmeasured from the base line.

When TB is unknown, TB may be takenequal to 0,03 LWL

LWL : Length of the ship, in m, at waterline

h1 : Ship relative motion in the consideredarea, in m, as defined in Sec 3, [2.1]

z : Load point calculation as defined in [4].

b) Element inside the hull:

The local internal pressures considering the adjacentcompartments individually loaded, without any coun-teraction

c) Testing conditions:

The internal testing pressures considered as acting alonewithout external load counteraction

d) Flooding conditions:

The internal flooding pressures on internal watertightelements considered without any counteraction on theinternal watertight element considered.

p pint 10 LWLTB h1– z–( )–=


NR 600, Ch 3, Sec 1

3.1.2 Ship draughtThe ship draught to be considered for the combination oflocal loads is to correspond to:• full load condition: when one or more cargo compart-

ments (oil tank, dry cargo hold, vehicle spaces) are con-sidered as being loaded and the ballast tanks empty

• light ballast condition: when one or more ballast tanksare considered as loaded and the cargo compartmentempty (in the absence of more precise information, theship’s draught in light ballast condition, in m, may betaken equal to 0,03 L).

4 Local load point location

4.1 General case for structure made of steel and aluminium alloys

4.1.1 Still water and wave loadsUnless otherwise specified, the local loads are to be calcu-lated: • for plate panels:

at the lower edge of the plate panels• for horizontal stiffeners:

at mid-span of the stiffeners• for vertical stiffeners:

at the lower and upper vertical points of the stiffeners.

4.1.2 Dynamic loadsUnless otherwise specified, the dynamic loads are to be cal-culated:• for plate panels:

at mid-edge of the plate panels• for longitudinal and transverse stiffeners:

at mid-span of the stiffeners.

4.2 General case for structure made of composite materials

4.2.1 Still water and wave loads

Unless otherwise specified, the local loads are to be calcu-lated:

• for plate panels:

at the lower edge of the plate panel for monolithic, andat the middle of the plate panels for sandwich

• for horizontal stiffeners:

at mid-span of the stiffeners

• for vertical stiffeners:

at the lower and upper vertical points of the stiffeners.

4.2.2 Dynamic loads

Unless otherwise specified, the dynamic loads are to be cal-culated:

• for plate panels:

at mid-edge of the plate panels

• for longitudinal and transverse stiffeners:

at mid-span of the stiffeners.

4.3 Superstructure and deckhouses

4.3.1 For superstructure and deckhouses, lateral pressuresare to be calculated for all type of materials at:

• mid-height of the bulkhead for plating

• mid-span for horizontal and vertical stiffeners.


NR 600, Ch 3, Sec 2

SECTION 2 HULL GIRDER LOADS

Symbols

LWL : Length at waterline at full load, in m

LHULL : Length of the hull from the extreme forward tothe extreme aft part of the hull, in m

BWL : Waterline breadth, in m, as defined in Ch 1, Sec1, [4.2.2]

BST : Waterline breadth of struts of swath, in m, asdefined in Ch 1, Sec 1, [4.2.2]

BSF : Moulded breadth of the submerged float ofswath, in m, as defined in Ch 1, Sec 1, [4.2.4]

CB : Total block coefficient as defined in Ch 1, Sec 1,[4.5]

As a rule, the value of Cb is to be taken at leastequal to 0,5 in the present Section

Δ : Full load displacement, in t, at scantling draughtin sea water (ρ = 1,025 t/m3)

Δlight : Light ship weight, in t. For the purpose of thepresent section, the light ship weight includeslubricating oil, fresh and feed water

Δb : Total displacement of the ship in ballast condi-tion, in t

T : Draught, at full load displacement, in m, meas-ured at the midship transverse section. In thecase of ship with a solid bar keel or equivalent,the draught is to be measured from the mouldedbase line (horizontal line tangent to the upperface of bottom plating) to the full load waterline

DW : Maximum deadweight of the ship, in t, equal tothe difference between the full load displace-ment and the light ship weight

n1 : Coefficient navigation depending on theassigned navigation notation, defined in Ch 1,Sec 1, [3.1.1]

g : Gravity acceleration taken equal to 9,81 m/s2.

1 General


1.1.1 Hull girder loads considered in the present Rules are:

• still water loads: induced by the longitudinal distribu-tion of the lightship, the internal loadings (cargo andballast) and the buoyancy in still water

• wave loads: induced by encountered waves in head seaand in addition for multihull in quartering sea

• impact loads: induced by bottom impact in waves (forhigh speed ship only)

• digging in wave loads: induced by encountered waveswhen the fore part of each float burying into the wave(for multihull ship only)

• wave acting on twin-hull for swath.

1.1.2 These different hull girder loads are to be combinedas defined in [3] in order to check:

• the longitudinal hull girder scantlings, and

• in addition, for multihull, the transverse structure ofplatform and extra check of longitudinal float girderscantlings.

2 Calculation convention

2.1 Sign conventions of global bending moments and shear forces

2.1.1 The sign conventions of bending moments and shearforces, at any ship transverse section, induced by the hullgirder loads are as shown in Fig 1, namely:

• the bending moment M is positive when it induces ten-sile stresses in the strength deck (hogging bendingmoment); it is negative in the opposite case (saggingbending moment, inducing compression stresses in thestrength decks)

• the vertical shear force Q is positive in the case ofdownward resulting forces preceding and upwardresulting forces following the ship transverse sectionunder consideration; it is negative in the opposite case.

Figure 1 : Sign conventions of bending momentsand shear forces

Q :

M :

Aft Fore

(+)

(+)


NR 600, Ch 3, Sec 2

2.2 Designation of global bending moments and shear forces

2.2.1 Designation of global bending momentsThe designation of vertical bending moment is as follows:

• Bending moment in still water condition:

- MSWH for hogging condition

- MSWS for sagging condition

• Wave bending moment induced by head sea condition:

- MWH for hogging conditions

- MWS for sagging conditions

• Wave bending moment induced by quartering sea con-dition (for multihull only):

- MWQH for hogging conditions

- MWQS for sagging conditions

• Minimum combined bending moment induced byimpact in wave and still water conditions (for highspeed ship only):

- Vertical moment:

MminH for hogging conditions

MminS for sagging conditions

- Transverse torsional moment (for multihull only):

Mttmin

• Bending moment induced by digging in wave (for multi-hull only):

- MDWL for the bending moment applied to the float ofmultihull

- MDWT for the bending moment applied to the primarytransverse structure of the platform of multihull

• Transverse bending moment acting on twin-hull forswath: MQ

2.2.2 Designation of vertical shear forcesThe vertical shear forces Q are designed with the same suf-fix as defined for the bending moments in [2.2.1].

3 Combination of hull girder loads

3.1 Hull girder loads combination

3.1.1 Ship in displacement modeThe bending moments and the combinations to be consid-ered for the hull girder analysis are defined in Tab 1.

The shear forces and the combinations to be considered forthe hull girder analysis are based on the same principle thanthe combinations of the bending moments defined in Tab 1.

3.1.2 Sailing shipWhen the ship is fitted with masts for sailing navigation, thebending moments MRIG and the shear forces QRIG inducedby the standing rigging and to take into account for the hullgirder analysis are defined in NR500 Classification ofYachts.

These moments and shear forces are to be combined to theloads combinations defined in [3.1.1] as defined in NR500Classification of Yachts.

Table 1 : Hull girder load combinations for ship in displacement mode

3.2 Hull girder loads distribution

3.2.1 The hull girder loads defined in [3.1] are to beapplied along the ship from 0,25 L from the aft end to 0,7 Lfrom the aft end.Note 1: As a rule, the combination of hull girder loads from the aftperpendicular to 0,25 L and from 0,7 L to the fore perpendicularare overlooked and considered as equal to zero.

4 Still water loads

4.1 Cargo ship

4.1.1

a) General

As a rule, for cargo ship as defined in Ch 1, Sec 1,[1.1.2], the longitudinal distribution of still water bend-ing moments and shear forces for homogeneous loadingconditions at full load displacement and for ballast con-dition, subdivided into departure and arrival conditionsare to submitted to the Society.

The data necessary to calculate the still water bendingmoments and shear forces are to be submitted to theSociety for information.

When these informations are not available, the still waterbending moments and shear forces in full load and bal-last conditions may be taken as defined in [4.1.4].

b) Still water loads stamp

The longitudinal distribution of still water bendingmoments and shear forces are a basis for the hull girderstrength review. The values of these still water bendingmoments and shear forces considered for the structurereview (Rules or Designer value) are to be indicated onthe midship section drawing.

Ship condition Monohull ship Multihull ship

All type of ship

Head sea condition (hogging)

MSWH + MWH MSWH + MWH

Head sea condition (sagging)

MSWS + MWS MSWS + MWS

Quartering sea condition (hogging)

NA MSWH + MWQH

Quartering sea condition (sagging)

NA MSWS + MWQS

Digging in wave (hogging)

NA MSWS + MDWL

In addition, for ship in planing mode

Head sea condition (hogging or sagging)

MminH MminH (1)

Quartering sea condition NA Mttmin (1)

In addition, for swath

Transverse moment MQ

Note 1: NA: Not applicable(1) Not applicable to swath.


NR 600, Ch 3, Sec 2

4.1.2 For ships having alternate light and heavy cargo load-ing conditions, see Ch 1, Sec 1, [2.2.3].

4.1.3 Particular types of ship

Supply vessels, barges, fishing vessels and all types of shipsnot considered as cargo ships as defined in Ch 1, Sec 1,[1.1.2] but liable to carry loading or equivalent loads maybe however examined, for a hull girder loads in still waterpoint of view, with the present requirements for cargo shipswhen deemed necessary by the Society.

4.1.4 Bending moments MSWH and MSWS

a) Hogging conditions

The bending moment in hogging condition MSWH, inkN.m, and the maximum shear force QSWH, in kN, maybe calculated in ballast condition as follows:

where:

DWloci : Weight, in t, of ballasts considered

xi : Distance, in m, between the midship per-pendicular and the centre of gravity of con-sidered ballasts (the sign of xi is always to beconsidered positive).

Note 1: When the value of MSWH is negative, the bending momentMSWH is to be considered as a minimum sagging moment (inthis case, the ship is always in sagging condition in still water).

b) Sagging conditions

The bending moment in sagging condition MSWS, inkN.m, and the maximum shear force QSWS, in kN, maybe calculated in full load condition (for homogeneousloading case only) as follows:

where:

X : Distance, in m, taken equal to:

X1 : Distance, in m, between the aft perpendicu-lar of the ship and the aft boundary of thecargo holds

X2 : Distance, in m, between the aft perpendicu-lar of the ship and the fore boundary of thecargo holds.

Note 2: When the value of MSWS is positive, the bending momentMSWS is to be considered as a minimum hogging moment (inthis case, the ship is always in hogging condition in still water).

Note 3: These formulae are only to be used for ships havingmachinery spaces and superstructures located in the ship aftpart.

4.2 Non-cargo ship

4.2.1 Bending moment MSWH and MSWS

a) Hogging conditions for monohull and catamaran

The bending moment in hogging condition MSWH , inkN.m, and the maximum shear force QSWH , in kN, maybe calculated as follows:

where:

LW = 0,5 (LWL + LHULL)

CW = 0,625 (118 − 0,36 LW) LW 10−3

b) Sagging conditions for monohull and catamaran

The bending moment in sagging condition MSWS , inkN.m, and the maximum shear force QSWS , in kN, maybe taken equal to:

MSWS = QSWS = 0

c) Hogging and sagging conditions for swath

The bending moments and shear forces for swath are tobe calculated as defined in a) and b) using the breadthBSF instead of BWL in the formulae.

5 Wave loads

5.1 General

5.1.1 Ship in displacement modeWave loads are induced by encountered waves in head sea.

The design encountered waves, considered with a probabil-ity level of 10−5, is represented by an equivalent static wavedefined in [5.2.2].

As an alternative, the Society may accept the values of waveinduced loads derived from direct calculations, when justi-fied on the basis of the ship’s characteristics and intendedservice. The calculations are to be submitted to the Societyfor approval.

5.1.2 Ship in planing modeIn addition to the calculation carried out as defined in[5.1.1], the combined bending moment and shear forcesinduced by impact loads are to be calculated according to[6.1] for high speed ship in planing mode.

As an alternative, the Society may accept the values ofimpact loads derived from direct calculations, when justi-fied on the basis of the ship’s characteristics and intendedservice. The calculations are to be submitted to the Societyfor approval.

5.1.3 Additional wave loads for multihullWave loads are induced by encountered waves in quarter-ing sea.

The design encountered waves, considered with a probabil-ity level of 10−5, is represented by an equivalent static wavedefined in [5.3.1].

MSWH 5 0 28LWLΔlight, Σ xiDWloci( ) 0 198LWLΔb,–+[ ]=

QSWH4MSWH

LWL

-----------------=

MSWS 5 0 28LWLΔlight, XDW 0 225LWLΔ,–+[ ]=

QSWS4MSWS

LWL

----------------=

X0 5LWL, X1–( )2 X2 0 5LWL,–( )2+

2 X2 X1–( )----------------------------------------------------------------------------------=

MSWH 0 8 0 25CWLW2BWLCb,( ),=

QSWH4MSWH

LWL

-----------------=


NR 600, Ch 3, Sec 2

As an alternative, the Society may accept the values of waveinduced loads and impact loads derived from direct calcu-lations, when justified on the basis of the ship’s characteris-tics and intended service. The calculations are to besubmitted to the Society for approval.

In addition to the moment defined in head sea condition,torsional moments applied to the platform of multihull(inducing bending moment and shear force in the floats andin the primary transverse cross structure of the platform) areto be calculated according to the following hypotheses:

• For multihull:

- in quartering sea condition: the forward perpendicu-lar of one float and the aftward perpendicular of theother float are on the crest of the wave (see [5.3])

- digging in wave: the fore parts of each float bury intothe wave to a depth as defined in [6.2.1].

• In addition for swath:

- wave acting on twin-hull (see [6.2.2]).

5.2 Wave loads in head sea condition

5.2.1 Wave loads in head sea condition

The bending moments and shear forces induced by wave inhead sea condition are calculated according to the follow-ing hypotheses:

• the forward and aftward perpendiculars of the hull areon the crest (sagging conditions), or

• the forward and aftward perpendiculars of the hull areon the trough (hogging conditions).

5.2.2 Wave characteristics for head sea condition

The characteristics of the encountered wave to consider inhead sea condition (equivalent static wave) are as follows:

• sinusoidal type

• wave length LW , in m, equal to:


• wave height CW (crest-to-trough), in m, equal to:

CW = 0,625 (118 − 0,36 LW) LW 10−3

5.2.3 Bending moments and shear forces

a) Hogging conditions for monohull ship

The maximum values of the wave bending moment inhogging condition, MWH , in kN.m, and the shear forceQWH , in kN, along one float in head sea condition areobtained from the following formulae:

MWH = 0,25 n1 CW LW2 BWL CB

QWH = 0,80 n1 CW LW BWL CB

b) Sagging conditions for monohull ship

The maximum values of the wave bending moment insagging condition, MWS , in kN.m, and the maximumshear force QWS , in kN, along one float in head sea con-dition are obtained from the following formulae:

MWS = − 0,25 n1 CW LW2 BWL CB

QWS = − 0,80 n1 CW LW BWL CB

where:

CW : Wave height, in m, as defined in [5.2.2]

LW : Wave length, in m, as defined in [5.2.2]

BW : Breadth at waterline, in m, of one float

c) Bending moment and shear forces for catamaran

The values of the wave bending moments and shearforces for catamaran are to be calculated as defined ina) and b) increased by 10%

d) Bending moment and shear forces for swath

The values of the wave bending moments and shearforces for swath are to be calculated as defined in c)using the breadth BST instead of BWL in the formulae.

5.3 Wave loads in quartering sea for multihull

5.3.1 Wave characteristics for quartering sea

The characteristics of the encountered wave to consider inquartering sea condition (equivalent static wave) are as fol-lows:

• sinusoidal type

• wave length LWQ , in m, resulting from the quarteringwave position and defined as follows (see Fig 2):

where:

LW : Wave length, in m, as defined in [5.2.2]

BE : Distance, in m, between the float axes (seeFig 2)

• wave height CWQ (crest-to-trough), in m, equal to:

CWQ = 0,625 (118 − 0,36 LWQ) LWQ 10−3

5.3.2 Bending moments and shear forces on multihull

a) Bending moments and shear forces for catamaran

The bending moments, in kN.m, and the shear forces, inkN, are to be calculated as follows:

• in hogging conditions:

MWQH = n1 CWQ LW2 BWL CB

QWQH = 1,60 n1 CWQ LW BWL CB

• in sagging conditions:

MWQS = − n1 CWQ LW2 BWL CB

QWQS = − 1,60 n1 CWQ LW BWL CB

where:

CWQ : Wave height (crest-to-trough), in m, asdefined in [5.3.1]

LWQ : Wave length, in m, as defined in Fig 2

LW : LW = 0,5 (LWL + LHULL)

LWQ2LWBE

LW2 BE

2+-----------------------=


NR 600, Ch 3, Sec 2

b) Bending moments and shear forces along the floats andin the platform for catamaranThe bending moments and shear forces along the floatsand the bending moments and shear forces in the primarytransverse cross structure of the platform are to be deter-mined by a beam model as defined in Ch 4, Sec 2, [4.3].The beam model is to be loaded by forces F, in kN, asshown on Fig 3, where F is successively equal to:F = MWQH / LWL

F = MWQS / LWL

with:

MWQH , MWQS : Bending moments, in kN.m, defined in a)here above.

c) Bending moments and shear forces along the floats andin the platform for swath

The bending moments and the shear forces for swath areto be calculated as defined in b) using the breadth BST

instead of BWL in the formulae of bending momentsMWQH and MWQS .

Figure 2 : Wave length for multihull

Figure 3 : Wave loads for platform multihull

BE

WaveTrough

WaveCrest

WaveTrough

CW2

LWQ

CW2

Wave direction

��

��

��


NR 600, Ch 3, Sec 2

6 Additional specific wave hull girder loads

6.1 Additional wave loads for high speed ship in planing mode

6.1.1 Minimum bending moments in head sea condition

a) Monohull

For monohull high speed ship as defined in Ch 1, Sec 1,[1.1.4], the minimum combined bending momentsMminH and MminS , in kN.m, and the shear forces QminH

and QminS , in kN, in planing hull mode (due to stillwater plus wave induced loads plus impact loads) are tobe not less than the following values:

• in hogging condition:

• in sagging condition:

where:

aCG : Vertical design acceleration at LCG,

expressed in g, as defined in Sec 3, [3.3.4]

LCG : Midship perpendicular as defined in Ch 1,Sec 1, [4.1.3].

The minimum water bending moments and shear forcesare to be applied along the ship from 0,25 L to 0,7 Lfrom the aft end.

b) Catamaran

For high speed ship catamaran as defined in Ch 1, Sec 1,[1.1.4], the minimum combined bending momentsMminH and MminS , in kN.m, and the shear forces QminH

and QminS , in kN, in planing hull mode (due to still waterplus wave induced loads plus impact loads) applied toone float are to be taken equal to the values defined in[6.1.1] reduced by half.

6.1.2 Minimum bending moments in quartering sea condition (for catamaran only)

a) Bending moment

For high speed ship catamaran as defined in Ch 1, Sec 1,[1.1.4], the minimum transverse torsional moment, inkN/m2, due to wave induced loads plus impact loads isnot to be less than:

Mttmin = 0,125 Δ LWL acg g

where:

acg : Design vertical acceleration as defined inSec 3, [3.3.4]. acg need not be taken greaterthan 1,0 g in this formula

b) Bending moments and shear forces along the floats andin the platform

The bending moments and the shear forces along thefloats and the bending moments and shear forces in theprimary transverse cross structure of the platform are to bedetermined by a beam model as defined in Ch 4, Sec 2,[4.3].

The beam model is to be loaded by forces F, in kN, asshown on Fig 3, where F is successively equal to:

F = Mttmin / LWL

F = − Mttmin / LWL

6.2 Additional wave loads for multihull

6.2.1 Digging in wave loads

a) Application

The digging in wave loading corresponds to the situa-tion where the multihull sails in quartering head sea andhas the fore end of the floats burying themselves into theencountered waves.

b) Bending moments for catamaran

As a rule, the bending moment due to digging in wavesmay be not calculated and overlooked for catamaranhaving a front platform located at a distance from theforward end of floats of less than 5% of LWL.

The bending moment MDWL , in kN.m, and the shearforce QDWL , in kN, in the float and in the platform of thecatamaran are to be calculated by a beam model asdefined in Ch 4, Sec 2, [4.3], taking into account the fol-lowing fore float loading (see Fig 4):

• for the float the more sunk in the water:

• for the float the less sunk in the water:

where:

F’ : Vertical Archimedian overpressure force, inkN, equal to:

F’’ : Horizontal Archimedian overpressure force,in kN, equal to:

F’’ = F’ cos 80°

d : Length, in m, of digging in water, equal tothe distance between the extreme fore endof each float and the forward part of theplatform

MminH 0 55ΔLWL CB 0 7,+( ) 1 aCG+( ),=

QminH3.2MminH

LWL

-----------------------=

MminS 0– 55ΔLWL CB 0 7,+( ) 1 aCG+( ),=

QminS3.2MminS

LWL

----------------------=

Fv8F′

3LW

----------=

Fh8F′ ′

3LW

----------=

Fv4F′

3LW

----------=

Fh4F′ ′

3LW

----------=

F' 1 8, gΔdAp

δ1 δ2+--------------------------- n1⋅=


NR 600, Ch 3, Sec 2

Figure 4 : Loading of multihull due to digging in wave

Ap : Pitch amplitude, in rad, as defined in Sec 4,[2.1.5]

δ1, δ2 : Vertical height of the digging in wave, in m,of a point located at d/2 abaft fore end ofeach float calculated as follows:

with:


The vertical and horizontal linear loads Fv and Fh are tobe applied from the fore part of the floats on a distribu-tion length equal to LWL / 4, as shown on Fig 4.

Note 1: For non conventional location of the fore part of the plat-form, the Society may decide to consider another load distribu-

tion, on a case-by-case basis.

c) Bending moments for swath

The bending moment MDWL , in kN.m, and the shearforce QDWL , in kN, in the float and in the platform of theswath are to be calculated as defined in b), taking intoaccount a vertical Archimedian over pressure F’, in kN,equal to:

6.2.2 Bending moments acting on twin-hull connections of swath

The bending moment MQ , in kN.m, applied along the plat-form structure of swath is to be taken equal to:

MQ = hM Fq

where:

hM : Half the draught T, in m, plus the distance fromthe waterline at draught T to the midpoint of theplatform structure (see Fig 5)

Fq : Beam side force, in kN, equal to:

Fq = 12,5 n1 T Δ2/3 d LS

with:

d = 1,55 − 0,75 tanh (Δ / 11000)

LS = 2,99 tanh (λ − 0,275)

λ = 0,137 Alat / (T Δ1/3)

Alat : Lateral surface, in m2, projected ona vertical plane of one hull with thatpart of strut or struts below thewaterline at draught T.

Figure 5 : Side beam force

Fv

Fh

LWL / 4

d = length indigging in water

Fv

Fh

δ113---LWAp=

δ216---LW 16otan=

F' 1 5, gΔ 0( 2LWL )Ap,δ1 δ2+

------------------------------------------------- n1⋅=�

��

��

��

��


NR 600, Ch 3, Sec 3

SECTION 3 LOCAL EXTERNAL PRESSURES

Symbols


LHULL : Length of the hull from the extreme forward tothe extreme aft part of the hull, in m

Base Line: As a rule, the base line is a fictive line located atthe lower point of the hull bottom where z = 0(see Fig 1)


CW = 0,625 (118 − 0,36 LW) LW 10−3


BWL : Waterline breadth, in m, as defined in Ch 1,Sec 1, [4.2.2]

D : Depth, in m, as defined in Ch 1, Sec 1, [4]

Δ : Full load displacement, in t, at scantling draughtin sea water (ρ = 1,025 t/m3)

T : Draught, at full load displacement, in m, meas-ured from the base line (see Fig 1)

TB : Draught, at ballast displacement, in m, meas-ured from the base line (see Fig 1)

If TB is unknown, TB may be taken equal to0,03 LWL

n : Coefficient navigation depending on theassigned navigation notation, defined in Ch 1,Sec 1, [3.1.1]

z : Z co-ordinate, in m, at the calculation point asdefined in Sec 1, [4]

ρ : Sea water density, taken equal to 1,025 t/m2

g : Gravity acceleration taken equal to 9,81 m/s2

V : Maximum ahead service speed, in knots

n : Coefficient navigation depending on theassigned navigation notation, defined in Ch 1,Sec 1, [3.1.1].

1 General

1.1 Sea pressures

1.1.1 The local sea pressure considered in the presentRules are still water loads (due to hydrostatic external seapressure in still water), and wave loads (due to wave pres-sure and ship motions).

1.2 Dynamic loads

1.2.1 The dynamic loads are loads which have a durationshorter than the period of wave loads and are constituted by:

• side shell impacts and, for multihull, platform bottomimpact: to be calculated for the plating and the second-ary stiffeners only (see [3.1])

• bottom impact pressure on flat bottom forward area: tobe calculated for the structural elements of forward bot-tom, where applicable (see [3.3])

• bottom slamming pressure: to be calculated for thestructural elements of the bottom of high speed ship inplaning hull mode as defined in Ch 1, Sec 1, [1.1.4] (see[3.3]).

Figure 1 : Z co-ordinate at the calculation point

��

�

��

� �

��

��


NR 600, Ch 3, Sec 3

2 Sea pressures

2.1 Ship relative motions

2.1.1 General

Ship motions are defined, with their sign, according to thereference co-ordinate system in Ch 1, Sec 1, [5] and areassumed to be periodic.

The ship relative motions h1 are the vertical oscillatingtranslations of the sea surface on the ship side. It is meas-ured, with its sign, from the waterline at draught T and maybe assumed as being:

• symmetrical on the ship sides (upright ship conditions)

• with an amplitude equal to the half of the crest tothrough of the encountered wave.

The ship relative motions h1, in m, are to be calculated forcargo and non-cargo ships as defined in Tab 1.

2.2 Sea pressures

2.2.1 Bottom and side shell

The still water and wave pressures on bottom and side shellin the different longitudinal parts of the hull are obtained, inkN/m2, as follows:

• for bottom structure:

Note 1: In case of important deadrise angle, the bottom pressuresmay be calculated as defined for the side shell structure.

• for side shell structure:

the greater value obtained from the following formulae,without being taken greater than the pressure calculatedfor the bottom:

PS = Pdmin

where:

z0 : Distance, in m, between the base line and thebottom hull in the considered section (see Fig 1).z0 may be taken negative if the calculation pointis located below the base line

z : Distance, in m, between the base line and thecalculation point in the considered section (seeFig 1)

Pdmin : Minimum sea pressure on exposed deck, inkN/m2, as defined in [2.2.2], in the consideredsection, with ϕ1 and ϕ2 taken equal to 1,00

h1 : Ship relative motion, in m, in the different longi-tudinal parts of the hull as defined in Tab 1

AR : Roll angle, in deg, to be taken equal to:

• for monohull cargo ship: AR = 20°

• for monohull non-cargo ship: AR = 25°

• for catamaran: AR = 10°

• for swath: AR = 5°

h2 : Parameter, in m, equal to:

• for monohull:

h2 = 0

• for catamaran (for internal side shell andplatform bottom):

• for swath:

where:

BWL : Waterline breadth, in m, at full loadwaterline at considered section (seeFig 2)

Bi : Distance, in m, between internalside shells at waterline consideredtransverse section (see Fig 2).

Table 1 : Ship relative motion h1

PS ρg T( h1 h2+ + z0 )–=

PS ρg T h1 h2 z–+ +( )=

PS ρg TBWL

2---------+ ARsin z–

=

h2BWL T h1+( )CB

Bi

------------------------------------=

h2BST T h1+( )CB

Bi

-----------------------------------=

Location Relative motion h1, in m, for cargo ship Relative motion h1, in m, for non-cargo ship

From aft part to 0,25 LwL

From 0,25 LwL to 0,70 LwL (1)

From 0,70 LwL to 0,85 LwL

From 0,85 LwL to fore part

Note 1: The coefficient CT is to be taken equal to:• 1,00 for monohull• 1,20 for catamaran• 0,75 for swath(1) The value of h1,m is not to be taken greater than the minimum of T and D − 0,9 TB

h1 A, 0.63 4.35CB

----------- 3.25– h1 m, h1 m,≥= h1 A, 1.1h1 m,=

h1 m, 0.36nCW= CB 0.7+( ) h1 m, 0.38CW 0.3+( )n=

h1 E, h1 m, 0.125h1 FE,+ h1 FE,≤= h1 E,1.4h1 m, 0.7h1 FE,+

2----------------------------------------------=

h1 FE, 1.2h1 m,4.35

CB

----------- 3.25– CT= h1 FE, 1.7h1 m,

7.6CB

0.1----------- 6.4– CT=


NR 600, Ch 3, Sec 3

Figure 2 : Breadths BWL and Bi for multihull

2.2.2 Exposed deck

The local external loads, in kN/m2, on exposed decks areobtained from the following formula:

pd = (p0 − 10 zd) ϕ1 ϕ2 ϕ3 > pdmin

where:

p0 : Sea pressure, in kN/m2, in the considered sec-tion calculated at the base line according to[2.2.1] (z0 taken equal to 0)

zd : Vertical distance, in m, between the deck andthe base line at the considered transverse section

ϕ1 : Coefficient for pressure on exposed deck, equalto:

• freeboard deck: ϕ1 = 1,00

• top of lowest tier: ϕ1 = 0,75

• top of second tier: ϕ1 = 0,56

• top of third tier: ϕ1 = 0,42

• top of fourth tier and above: ϕ1 = 0,32

ϕ2 : Coefficient taken equal to 0,55

ϕ3 : Reduction coefficient, equal to:

• when the deck is partially protected (notdirectly exposed to green sea effect): ϕ3 = 0,70

• in the other case: ϕ3 = 1,00

pdmin : Minimum sea pressure on deck, in kN/m2,equal to:

• from aft part to 0,70 LWL:

pdmin = 27,5 n ϕ1 ϕ2 ϕ3 > 5

• from 0,70 LWL to fore part:

pdmin = 29,5 n ϕ1 ϕ2 ϕ3 > 7

2.2.3 Exposed deck with cargoAs a rule, the local external loads, in kN/m2, on exposeddeck supporting cargo are to be taken equal to the sum oflocal:• external load on exposed deck as defined in [2.2.2]• cargo load as defined in Sec 4, [3].

When the exposed deck is partially protected by the cargoand is not directly exposed to the green sea effect, the exter-nal load defined in [2.2.2] may be reduced by 30% for thecalculation of the total deck external load.

2.2.4 Other type of exposed deckThe local external loads of exposed deck which are notaccessible to the passengers and not directly exposed to seapressure may be taken equal to 1,3 kN/m2.

The local external loads on superstructures decks aredefined in Ch 5, Sec 1.

Local forces on deck induced by containers, lashing, wheelloads... are to be calculated as defined in Sec 4.

3 Dynamic loads

3.1 Side shell impact and platform bottom impact

3.1.1 GeneralThe side shell impact and the platform bottom impact (formultihull) are local loads and represents the local waveimpact acting on the hull, independently of the shipmotion.

These impacts are considered as locally distributed like awater column of 0,6 m diameter and is to be applied on theside shell, on all the length of the ship, above the minimumdraught operational.

3.1.2 Impact calculation on side shellThe impact pressure pssmin , in kN/m2, acting on the sideshell is not to be less than:

pssmin = pss1 K2

where:pss1 : Design impact pressure on side shell, in kN/m2,

equal to:pss1 = Ci n

Ci : Dynamic load distribution factor defined Tab 2K2 : Area factor defined in [3.3.3], b).

Note 1: The minimum values to be taken into account for sidescuttles are:

• 0,50 for glass

• 0,35 for plastic.

Table 2 : Value of Ci

��

��

��

from T to T + 1 m

from T + 1 m to T + 3 m

above

from aft part to 0,70 LWL

60 45 30

from 0,70 LWL to fore part

80 60 30


NR 600, Ch 3, Sec 3

Figure 3 : Loads areas for impact pressure on multihull

3.1.3 Impact calculation on internal side shell and platform bottom of multihull

The impact pressure pssmin, in kN/m2, acting on the internalside shell and on the platform bottom is not to be less than:

pssmin = pss1 K2

where:

pss1 : Design impact pressure on internal side shell incross deck, in kN/m2, equal to:

pss1 = Ci n

Ci : Dynamic load distribution factor defined as fol-lows (see Fig 3):

• in area 5: Ci = 80

• in area 6: Ci = 50

• in area 7: Ci = 120

Note 1: For swath, the dynamic load distribution factor Ci maybe taken equal to 30 in areas 5, 6 and 7 for platformbottom and side shell located above T + 3 m.

K2 : Area factor defined in [3.3.3], b).

3.2 Bottom impact pressure for flat bottom forward area

3.2.1 ApplicationThe present requirements are applicable for ships having:

• a navigation notation other than sheltered area

• a flat bottom shape on the forward hull body, and

• a minimum forward draught, in m, in ballast conditionor in partial loading operation less than 0,04 L.

Note 1: For pontoon shaped ships, when a reduction of the speed isprovided in relation with the sea state to avoid bottom impactpressure for flat bottom area, the present requirements are notapplicable.

3.2.2 Area to be consideredThe flat bottom area is considered as the area limited to:• longitudinally: area in aft of the fore end, from 0,05 LWL

to 0,25 (1,6 − CB) LWL , without being taken less than0,2 LWL nor greater than 0,3 LWL

• transversely and vertically: over the whole flat bottomand the adjacent zones up to a height from the base linenot less, in mm, than 2 LWL , limited to 300 mm.

3.2.3 Bottom impact pressure for flat bottom areaa) Plating and secondary stiffeners

The bottom impact pressure pBI in kN/m2, for the platingand secondary stiffeners is to be obtained from the fol-lowing formula:

where:• general case:

with 0 < C1 ≤ 1

TFmin : Minimum forward draught, in m, meas-ured from the base line

z0 : Distance, in m, between the base lineand the bottom hull in the consideredtransverse section (see Fig 1)

• non propelled units: C1 = 0,19

b) Primary stiffeners

The bottom impact pressure in kN/m2, for the primarystiffeners is to be taken equal to 0,3 pBI , where pBI is thebottom impact pressure for plating and secondary stiff-eners calculated in a).

area 6

area 5area 7area 5

1 m

LWD / 32 LWD / 3

LWD

area 5 area 7

Cross deck

internal side shell

external side shell

internal side shell

external side shell

pBI 62C1LWL0 6,=

C1

119 2300TFmin z0–

LWL

-----------------------–

78 1800TFmin z0–

LWL

-----------------------+-----------------------------------------------------=


NR 600, Ch 3, Sec 3

3.3 Bottom slamming for high speed ship

3.3.1 General

Slamming phenomenon on bottom area are to be consid-ered on high speed ship as defined in Ch 1, Sec 1, [1.1.4],and are induced by heave acceleration in planing hullmode

As a rule, bottom slamming loads are to be calculated on bot-tom area, up to the limit of bilges or hard chines, and from thetransom to the fore end, for monohull and catamaran.

3.3.2 Bottom slamming pressures

The slamming pressure psl , in kN/m2, considered as actingon the bottom of high speed ship in planing hull mode is tobe not less than:

Psl = Psl1 K2

where:

K2 : Area factor defined in [3.3.3], b)

Psl1 : Design bottom slamming pressure, in kN/m2,equal to:

Psl1 = 100 T K1 K3 aCG

K1 : Dynamic load factors defined in [3.3.3], a)

K3 : Bottom shape factor defined in [3.3.3], c)

aCG : Vertical design acceleration at LCG , expressed ing, defined in [3.3.4].

3.3.3 Dynamic load factors

The dynamic load factors Ki are to be calculated as follows:

a) Distribution factor K1

The longitudinal slamming pressure distribution factorK1 for the calculation of the design bottom slammingpressure in planing hull mode is defined in Tab 3.

b) Area factor K2

The area factor K2 is a coefficient taking into account thedimension and the material of the structure elementsubmitted to bottom slamming load. This factor isdefined by the following formula:

where:

sa : Area, in m2, supported by the element (plat-ing, stiffener, floor or bottom girder)

For plating, the supported area is the spacingbetween the stiffeners multiplied by theirspan (the span is not to be taken more thanthree times the spacing between the stiffeners)

Sr : Reference area, in m2, equal to:

K2min : Minimum values taken equal to:

• for steel and aluminium structure:

K2min = 0,50 for plating and side scuttle

K2min = 0,45 for secondary stiffeners

K2min = 0,35 for primary stiffeners

• for composite and plywood structure:

K2min = 0,35 for plating and sidescuttle,and for secondary and primary stiffeners.

c) Bottom shape factor K3

The bottom shape and deadrise factor K3 for the calcula-tion of the design bottom slamming load is defined bythe following formula:

where:

αd : Deadrise angle at the considered transversesection, in deg (see Fig 4)

αdCG : Deadrise angle, in deg, measured at ship’slongitudinal centre of gravity LCG (see Fig 4)

Values taken for αd and αdCG are to be between 10° and50°.

Table 3 : Value of K1

3.3.4 Design vertical acceleration aCG at LCG

a) Design vertical acceleration:

The design vertical acceleration at LCG, aCG (expressed ing), is to be defined by the Designer and is to correspondto the average of the 1% highest accelerations in themost severe sea conditions expected, in addition to thegravity acceleration.

The following value of aCG may be used, taking intoaccount the type of design and the sea conditions, whenthe Designer value is not available:

where foc and soc are values given in Tab 4 and Tab 5.

Note 1: Lower values of aCG may be accepted by the Society if jus-

tified on the basis of model tests and full-scale measurements.

b) Vertical acceleration stamp:

The value of the vertical acceleration at LCG is a basis forthe structure scantling review within the scope of classi-fication. The value of this vertical acceleration aCG con-sidered for the structure review (Rule or Designer value)is to be indicated on the midship section drawing.

K2 0 455 0 35, u0 75, 1 7,–u0 75, 1 7,+---------------------------–, K2min>=

u 100sa

Sr

----=

Sr 0 7ΔT---,=

Location K1

from aft part to 0,25 LWL 0,60

from 0,25 LWL to 0,70 LWL 1,00

from 0,70 LWWL to 0,85 LWL 1,00

from 0,85 LWL to fore part 0,75

K3 70 αd–( ) 70 αdCG–( )⁄ 1≤=

aCG foc soc⋅ VLWL

------------=


NR 600, Ch 3, Sec 3

Figure 4 : Deadrise angles αdCG and αd

BL : Base line at LCG ; BLS : Base line at the considered transverse section

Table 4 : Values of foc

3.3.5 Information in relation to the design vertical acceleration

It is the Designer responsibilty to specify the range of speedswhere the ship is in planing hull mode and to define a rela-tion between the speed and the significant wave height thatprovides a maximum vertical acceleration less than thedesign value considered for the hull structure review. Thisrelation may be determined on the basis of the results ofmodel test or full-scale measurements.

For information only, where these Designer’s data are notavailable, the following formula may be used to define arelation between a considered speed Vx and the significantwave height HS compatible with the design acceleration inplanning hull mode considered for the hull structure check:

where:

HS : Significant wave height, in m, corresponding tothe considered speed Vx

αdCG : Deadrise angle, in deg, at LCG. In this formula,αdCG is to be taken between 10° and 30°

τ : Trim angle during navigation, in deg, to betaken not less than 4°

BW : Maximum breadth at full load waterline. Forcatamarans, BW is to be taken as the sum of thebreadth of each hull.

The formula of HS is only valid if all the following relation-ships are simultaneously complied with:

• 3500 < Δ / (0,01 LWL)3 < 8700

• 3 < LWL / BW < 5

• 10° < αdCG < 30°

• 0,2 < HS / BW < 0,7

• 3,0 < V / (LWL)0.5 < 10,9

TT/2

Reference line fordeadrise anglemeasurement

T


T/2


T


T

BL

BL

BLS

BLS

Type of service

Passenger, Ferry, Cargo

Supply, Fishing

Pilot, Patrol

Rescue

foc 0,666 1,000 1,333 1,666

HS3555CBaCG

Vx

LWL

------------ 2

50 αdCG–( ) τ16------ 0 75,+

---------------------------------------------------------------------------------- 0 084,( )BW

T-------

–

T=


NR 600, Ch 3, Sec 3

Table 5 : Values of soc

Navigation notations (1) Unrestricted navigation Summer zone Tropical zone or coastal area (3) Sheltered area (4)

Sea area (5) 4 or 3 4 or 3 2 1

soc CF (2) 0,30 0,23 0,14

(1) The navigation notations refer to sea area based on significant wave heights Hs which are exceeded for an average of not more than 10% of the year:• sea area 4 Open-sea: Hs ≥ 4,0 m• sea area 3 Restricted open-sea: 2,5 m ≤ Hs < 4,0 m• sea area 2 Moderate environment: 0,5 m < Hs < 2,5 m• sea area 1 Smooth sea: Hs ≤ 0,5 m

(2) For passenger, ferry and cargo ship, their seaworthiness in this condition is to be ascertained. In general, value of soc should not be lower than the values given in this Table, where:

(3) Not applicable to ship with type of service “Rescue”(4) Not applicable to ship with type of service “Pilot, Patrol” or “Rescue”(5) For information only (see NR467 Steel Ships, Pt A, Ch 1, Sec 2 [5.2.8]).

CF 0 2, 0 6,V LWL⁄---------------------+ 0 32,≥=


NR 600, Ch 3, Sec 4

SECTION 4 LOCAL INTERNAL PRESSURES AND FORCES

Symbols

LWL : Length at waterline at full load, in mLHULL : Length of the hull from the extreme forward to

the extreme aft part of the hull, in mLW = 0,5 (LWL + LHULL)

CW = 0,625 (118 − 0,36 LW) LW 10−3

B : Moulded breadth, in m, as defined in Ch 1, Sec1, [4.2.1]

BWL : Waterline breadth, in m, as defined in Ch 1, Sec1, [4.2.2]

BE : Breadth between multihull floats, in m, asdefined in Ch 1, Sec 1, [4.2.3]

BSF : Moulded breadth, in m, of the submerged floatof swath


n : Navigation coefficient as defined in Ch 1, Sec 1,[3]

V : Maximum ahead service speed, in knotsg : Gravity acceleration taken equal to 9,81 m/s2

az : Vertical acceleration, in m/s2, defined in [2.2]ρ : Sea water density, taken equal to 1,025 t/m2.

1 Application

1.1 General

1.1.1 The local internal pressures and forces are based onship accelerations calculated on the basis of the presentSection.

1.1.2 High speed shipAs a rule, the local internal pressures and forces for highspeed ships are to be calculated taking into account theaccelerations in planing hull mode condition and in dis-placement hull mode condition.

2 Ship accelerations

2.1 Reference values

2.1.1 The reference values of the vertical and transverseaccelerations, and amplitude taken into account in thepresent Section are considered equal to the values given inthe present Article.

2.1.2 As an alternative, the Society may accept the valuesof ship accelerations derived from direct calculations orobtained from model tests, when justified on the basis of theship’s characteristics and intended service.

2.1.3 The motions and accelerations are defined:

• in displacement mode: in [2.1.4] to [2.1.7] and [2.2.1]

• in planing mode: in [2.2.2].

2.1.4 Motion and acceleration parameterThe motions and accelerations are based on a parameter aB

to be taken equal to:

where:

F : Froude’s number equal to:

Note 1: At a preliminary design stage when V is unknown, Fmay be taken equal to 0,33.

2.1.5 Heave

The heave acceleration aH , in m/s2, is obtained from the fol-lowing formulae:

• for cargo ship: aH = aB g

• for non-cargo ship: aH = 1,25 aB g

2.1.6 Pitch

The pitch acceleration αp , in rad/s2, is obtained from the fol-lowing formula:

where:

Ap : Pitch amplitude Ap , in rad, equal to:

Ap = (1 − LWL 10−3) CAp

with:

• CAp = 0,14 for monohull cargo ship

• CAp = 0,16 for monohull non-cargo ship

• CAp = 0,16 for catamaran (for cargo andnon-cargo ship)

• CAp = 0,21 for swath (for cargo and non-cargo ship)

Tp : Pitch period, in s:

• Tp = 0,56 (LWL)0,5 for monohull cargo ship

• Tp = 0,52 (LWL)0,5 for monohull non-cargo ship

• Tp = 0,51 (LWL)0,5 for catamaran (for cargoand non-cargo ship)

• Tp = 0,69 (LWL)0,5 for swath (for cargo andnon-cargo ship).

aB n 0 76F, 2.5CW

LWL

--------+ =

F 0 164 V LWL⁄( ), 0.33≤=

αp Ap= 2πTp-------

2

n


NR 600, Ch 3, Sec 4

2.1.7 Roll

The roll acceleration αR, in rad/s2, is obtained from the fol-lowing formula:

where:

AR : Roll amplitude, in rad:

• AR = 0,35 for monohull cargo ship

• AR = 0,43 for monohull non-cargo ship

• AR = 0,17 for catamaran (for cargo and non-cargo ship)

• AR = 0,08 for swath (for cargo and non-cargo ship)

TR : Roll period, in s, equal to:

where:

• δ = 0,35 B for cargo and non-cargo ship

δ = (0,3 BE BWL)0.5 for catamaran (for cargoand non-cargo ship)

δ = (0,3 BE BSF)0.5 for swath (for cargo andnon-cargo ship)

• GM = 0,13 BWL for cargo ship

GM = 0,22 BWL for non-cargo ship

GM = 1,10 BE for catamaran (for cargo andnon-cargo ship)

GM = 0,50 BE for swath (for cargo and non-cargo ship).

2.2 Vertical accelerations

2.2.1 Cargo and non-cargo ship

The vertical accelerations az , in m/s2, to take into accountin relation to the ship location areas are to be as defined inTab 1.

Table 1 : Vertical acceleration az

2.2.2 High speed shipThe vertical acceleration az , in m/s2, to take into account inrelation to the ship location for high speed ship is to betaken equal to the following values:

a) At speed in displacement mode:az as defined in [2.2.1] for cargo or non-cargo ship, asapplicable

b) At maximum speed in planing mode:az = g aV

where:aV = KV aCG

with:KV : Defined in Tab 2aCG : Design vertical acceleration at LCG as

defined in Sec 3, [3.3.4]LCG : Midship perpendicular as defined in Ch 1,

Sec 1, [4.1.3].

Table 2 : Value of KV

3 Internal loads

3.1 Liquids

3.1.1 Watertight bulkheadsThe local internal pressure, in kN/m2, on watertight bulk-heads, bottom and top of liquid capacity is to be taken equalto the greater value obtained from the following formulae:

where:ρL : Density of the liquid considered, in t/m3

aZ : Vertical acceleration, in m/s2, as defined in [2.2]

b : Longitudinal distance, in m, between the trans-verse capacity boundaries or transverse swashbulkhead, if any, satisfying the requirements in[3.1.2]

η : Acceleration coefficient to be taken equal to:• for ship in displacement mode: η = 0,8• for ship in planing mode: η = 0,4

zTOP : z co-ordinate, in m, of the highest point of thecapacity (see Fig 1)

z : z co-ordinate of the calculation point, asdefined in Sec 1, [4]

ppv : Setting pressure, in bar, of safety valves, if any

Locationaz , in m/s2

Cargo ship Non-cargo ship

from aft part to 0,25 LWL

from 0,25 LWL to 0,70 LWL

from 0,70 LWL to 0,85 LWL

from 0,85 LWL to fore part

αR AR= 2πTR-------

2

n

TR 2.2 δGM--------------=

aH2 αp

2 0 40LWL,( )2+ aH2 αp

2 0 30LWL,( )2+

aH2 αp

2 0 20LWL,( )2+ aH2 αp

2 0 20LWL,( )2+

aH2 αp

2 0 40LWL,( )2+ aH2 αp

2 0 30LWL,( )2+

aH2 αp

2 0 55LWL,( )2+ aH2 αp

2 0 50LWL,( )2+

Location KV

from aft part to 0,50 LWL 1,00



from 0,85 LWL to fore part 1,85

p ρL 0.15ηgb

2---- aZη zTOP z–( ) g zL z–( )+ +=

p ρL g azη+( ) zTOP z–( ) 100ppv 0.15ηgρLb

2----+ +=


NR 600, Ch 3, Sec 4

Figure 1 : z co-ordinates

zL = zTOP + 0,5 (zAP − zTOP)

with:

zAP : z co-ordinate, in m, of the top of air pipe (seeFig 1).

3.1.2 Swash bulkheadsThe local internal pressure, in kN/m2, acting on swash bulk-heads is obtained as follows:

• Transverse swash bulkhead:

• Longitudinal swash bulkhead:

where:

ρL : Density of the liquid considered, in t/m3

c : Longitudinal distance, in m, between transversebulkheads (watertight or swash)

bc : Transverse distance, in m, between longitudinalbulkheads (watertight or swash)

α : Ratio of lightening hole area to the total bulk-head area, not to be taken greater than 0,3

d0 : Distance, in m, to be taken equal to:

d0 = 0,02 L ≤ 1,00

3.2 Dry cargoes

3.2.1 Dry uniform cargoThe pressure p, in kN/m2, transmitted to the structure by dryuniform cargo is to be taken equal to the following formula:

where:

ps : Design pressure given by the Designer

When this value is not defined, ps may be takenequal to 6,9 hTB , where hTB is the compartmentheight at side

az : Vertical acceleration, in m/s2, as defined in [2.2]

η : Acceleration coefficient to be taken equal to:

• for ship in displacement mode: η = 1,0

• for ship in planing mode: η = 0,4

3.2.2 Dry bulk cargo

The pressure p, in kN/m2, transmitted to the structure by drybulk cargo is to be taken equal to the greater value obtainedfrom the following formulae:

where:

ρB : Density of the dry bulk carried, in t/m3

pDB : Design pressure on the double bottom, inkN/m2, given by the Designer

az , η : As defined in [3.2.1]

hb : Height, in m, from the bottom cargo hold, of therated surface of the bulk, to be taken equal to:

where:

Mc : Total mass of cargo, in t, in the con-sidered hold

c : Longitudinal distance, in m,between transverse hold bulkheads

bc : Transverse distance, in m, betweenlongitudinal hold bulkheads

ht : Height, in m, of the bulk cargo upper surface tobe taken equal to:

where:

ϕ : Angle of repose, in deg, of the bulkcargo considered drained andremoved (in absence of precise eval-uation, ϕ may be taken equal to 30°)

hz : Vertical distance, in m, from the bottom hold tothe calculation point

KB : Coefficient taken equal to:

• KB = 0,4 when the dry bulk pressure isapplied on a vertical structure element

• KB = 1,0 in the other cases.

dAP

ZTOP

ZAP

dAP

ZTOP

ZAP

p 4.4ρLnc 1 α–( )0.15 0.8gd0≥=

p 4.4ρLnbc 1 α–( )0.35 0.8gd0≥=

p ps 1azηg---------+

=

p pDB 1azηg---------+

=

p ρB g azη+( ) hb ht hz–+( )KB=

hb Mc cbcρB( )⁄=

htbc

4----- ϕ

2---tan=


NR 600, Ch 3, Sec 4

3.2.3 Dry unit cargo

The forces transmitted to the hull structures are to be deter-mined on the basis of the forces, in kN, calculated as fol-lows:

Fz = M (g + azη)

where:

az : Reference value of the vertical accelerationdefined in [2.2]

M : Total mass, in t, of the dry unit cargo considered

η : As defined in [3.2.1].

Where deemed necessary by the Society for dry unit cargolocated above the water line level, the horizontal and verti-cal forces applied to the dry unit cargo, in kN, induced byroll may be taken into account in addition to Fz.

In this case, the forces transmitted to the hull structure toadd to Fz, in kN, may be calculated as follows:

• Transverse force:

• Vertical force:

where:

M : Mass, in t, of the dry unit cargo considered

αR : Roll acceleration, in m/s2, as defined in [2.1.7]

y, z : Transverse and vertical co-ordinates of the cen-tre of gravity of the dry unit considered

Tmin : Minimum draught of the ship, in m.

3.3 Wheeled loads

3.3.1 Local forces

Caterpillar trucks and unusual vehicles are considered bythe Society on a case-by-case basis.

The load supported by the crutches of semi-trailers, han-dling machines and platforms is considered by the Societyon a case-by-case basis.

The forces transmitted through the tyres are comparable topressure uniformly distributed on the tyre print, whosedimensions are to be indicated by the Designer togetherwith information concerning the arrangement of wheels onaxles, the load per axle and the tyre pressures.

For vehicles on rails, all the forces transmitted are to be con-sidered as concentrated.

The forces FW, in kN, transmitted to the hull structure are tobe determined as follows:

• in general:

• in harbour conditions, for fork-lift trucks and vehicles onexternal ramp:

where:

M : Force, in t, applied by one wheel, calculated asfollows:

QA : Axle load, in t. For fork-lift trucks, the value ofQA is to be taken equal to the total mass of thevehicle, including the mass of the cargo han-dled, applied to one axle only

nW : Number of wheels for the axle considered

α : Coefficient taken equal to:

• in general case: α = 0,5

• for landing gears of trailers: α = 1,0

az : Reference value of the vertical accelerationdefined in [2.2].

4 Loads on deck

4.1 Exposed deck

4.1.1 The local external loads, in kN/m2, on exposed deckare to be as defined in Sec 3, [2.2.2].

4.2 Accommodation deck

4.2.1 The pressure on accommodation deck is obtained, inkN/m2, from the following formula:

where:

az : Reference value of the vertical accelerationdefined in [2]

η : As defined in [3.2.1]

ps : Pressure defined by the Designer, to be taken atleast equal to the values given in Tab 3.

Table 3 : Values of ps

4.3 Specific loads on deck

4.3.1 Specific loads on deck such as wheeled loads, dryunit cargo, containers, are to be determined as defined in[3].

FT 0 7MαR z Tmin–( ),=

FV 0 7MαRy,=

FW M g αaz+( )=

FW 1 1Mg,=

Type of accommodation deck ps , in kN/m2

Large public spaces such as restaurants, halls, cinema, lounges

5,0

Large rooms such as rooms with fixed furni-ture, games and hobbies rooms, hospitals

3,0

Cabins 3,0

Other compartments 2,5

MQA

nW

-------=

p ps 1azηg---------+

=


NR 600, Ch 3, Sec 4

4.3.2 Machinery spacesThe pressure on decks and platform located in the machineryspaces is obtained, in kN/m2, from the following formula:

where:az : Reference value of the vertical acceleration

defined in [2]η : As defined in [3.2.1]ps : Pressure defined by the Designer

When this value is not defined, ps may be takenequal to 10 kN/m2.

5 Testing loads

5.1 General

5.1.1 The testing loads acting on the structure subjects to tanktesting is obtained, in kN/m2, from the formulae in Tab 4.Compartment not defined in Tab 4 are to be tested inaccordance with NR467 Steel Ships, Pt B, Ch 5, Sec 6.

6 Flooding loads

6.1 General

6.1.1 The internal pressure pfl to be considered on thestructure of boundary of watertight compartment notintended to carry liquids (with exception of bottom and sideshell structure) is to be obtained, in kN/m2 from the follow-ing formula:

pfl = 1,5 ρ g n (zf − z) > 0,8 g d0

where:

zf : Z co-ordinate, in m, of the bulkhead deck (orfreeboard deck when there is no bulkhead deck)at side in way of the transverse section consid-ered. Where the results of damage stability cal-culations are available, the deepest equilibriumwaterline may be considered in lieu of the bulk-head deck

z : z co-ordinate of the calculation point

d0 : Distance, in m, to be taken equal to:

d0 = 0,02 LWL ≤ 1,0

Table 4 : Testing load values

p ps 1azηg---------+

=

Compartment or structure to be tested Still water pressure pST , in kN/m2

Double bottom tanks The greater of the following:pST = 10 [(zTOP − z) + dAP]pST = 10 (zbd − z)

Double side tanks, fore and after peaks used as tank, cofferdams The greater of the following:pST = 10 [(zTOP − z) + dAP]pST = 10 [(zTOP − z) + 0,3 H]

Tank bulkheads, deep tanks, fuel oil bunkers The greater of the following:pST = 10 [(zTOP − z) + dAP]pST = 10 [(zTOP − z) + 0,3 H]pST = 10 [(zTOP − z) + 10 pPV]

Fore peak not used as tank pST = 10 (zbd − z)

Watertight doors below freeboard or bulkhead deck pST = 10 (zbd − z)

Chain locker (if aft of collision bulkhead) pST = 10 (zTOP − z)

Independent tanks The greater of the following:pST = 10 [(zTOP − z) + dAP]pST = 10 [(zTOP − z) + 0,9]

Ballast ducts Ballast pump maximum pressure

Note 1:ZTOP : Vertical co-ordinate, in m, of the highest point of the tankZbd : Vertical co-ordinate, in m, of the bulkhead deck, or of the free board deck when there is no bulkhead deckdAP : Distance, in m, from the top of air pipe to the top of the compartmentppv : Setting pressure, in bar, of the safety relief valves, where relevantH : Height, in m, of the tank, with: 0,9 ≤ 0,3 H ≤ 2,4

For ships greater than 40 m, 0,3 H is not to be taken less than 2,4 m.


NR 600, Ch 3, Sec 4


NR 600

Chapter 4

HULL SCANTLING

SECTION 1 GENERAL

SECTION 2 GLOBAL STRENGTH ANALYSIS

SECTION 3 LOCAL PLATING SCANTLING

SECTION 4 LOCAL SECONDARY STIFFENER SCANTLING

SECTION 5 LOCAL PRIMARY STIFFENER SCANTLING

SECTION 6 STIFFENER BRACKETS SCANTLING

SECTION 7 PILLAR SCANTLING

APPENDIX 1 CALCULATION OF THE CRITICAL BUCKLING STRESSES


NR 600, Ch 4, Sec 1


SECTION 1 GENERAL

1 Materials

1.1 General

1.1.1 General

The requirements for the determination of the hull scant-lings defined in the present chapter are applicable to shiphull made totally or partly of:

• steel (ordinary or high tensile)

• aluminium alloys

• composites materials

• wood (strip planking or plywood).

Ships built with different hull materials (traditional woodenconstruction for example) are to be specifically consideredon a case-by-case basis.

Attention is drawn to the selection of building materialswhich is not only to be determined from strength considera-tion, but should also give consideration to structural fireprotection and associated class requirements or FlagAdministration requirements where applicable.

1.1.2 Characteristics of materials

The main characteristics of materials to consider for hullscantlings are defined in Ch 1, Sec 2.

2 Structure scantling approach

2.1 General

2.1.1 General case

As a rule, the global hull girder strength and the localstrength are examined independently.

2.1.2 Particular cases

The combination of global hull girder strength and the localstrength may be carried out as defined in Ch 1, Sec 3,[2.1.2]. In this case, the requirements defined in NR467Steel Ships, Chapter 7, dedicated for ship greater than 65 m,may be fully applied the Society.

2.2 Global strength analysis

2.2.1 Analysis

The global hull girder longitudinal strength and the globalstrength of multihull are to be checked according to Sec 2,taking into account the:

• global loads as defined in Ch 3, Sec 2, and

• permissible stresses and safety coefficients as defined inCh 2, Sec 3.

2.2.2 Check

The global strength analysis is carried out in order to check,for the elements contributing to the global hull strength, thehull girder stresses in relation to:

• the maximum permissible global stress, and

• buckling criteria.

2.3 Local scantling analysis

2.3.1 Analysis

The local scantling of panels, secondary stiffeners and pri-mary stiffeners is to be checked according to Sec 3 for plat-ing, Sec 4 for secondary stiffeners and Sec 5 for primarystiffeners, taking into account the:

• local loads as defined in Ch 3, Sec 3 for external pres-sure, Ch 3, Sec 4 for internal pressure and Ch 5, Sec 1for superstructures, and

• permissible stresses and safety coefficients as defined inCh 2, Sec 3.

The type of local lateral pressures to be considered are:

• wave loads

• dynamic loads:

- bottom slamming pressures for high speed ships,when slamming may occur

- side shell impacts (and platform bottom impacts formultihull) for all types of ships

• deck loads and superstructure pressures

• bulkhead and tank loads

• wheeled loads.

2.3.2 Check

The local strength analysis is carried out in order to check,for the plating, secondary and primary stiffeners, the localstresses in relation to:

• the maximum permissible local stress, and

• local buckling criteria, where applicable.

2.4 Specific cases

2.4.1 Specific scantling criteria in relation to the servicenotation of the ships are defined in Ch 5, Sec 4.

NR 600, Ch 4, Sec 2

SECTION 2 GLOBAL STRENGTH ANALYSIS

1 General

1.1 Application

1.1.1 The global strength analysis is to be carried out inorder to check the hull girder stress in relation to maximumpermissible stress and buckling stress (see [2.2] and [2.3]).

1.1.2 Material

The global strength analysis of monohull and multihull is tobe carried out taking into account:

• for steel structure: the present Section

• for aluminium structure: the present Section and NR561Aluminium Ships

• for composite structure: the present Section and NR546Composite Ships.

1.1.3 Application

a) Monohull ships and float of multihull:

For monohull ships and for floats of multihull, the globalhull girder longitudinal strength is to be examined in thefollowing cases:

• ships with length greater than 40 m, or

• ships having large openings in decks or significantgeometrical structure discontinuity at bottom ordeck, or

• ships with transverse framing systems, or

• ships with deck structure built with large spacing ofsecondary stiffeners, or

• cargo ship as defined in Ch 1, Sec 1, [1.1.2], or

• where deemed appropriate by the Society.

For ships not covered by the above cases, the hull girderstrength is considered satisfied when local scantlings arein accordance with requirements defined in Sec 3 andin Sec 4.

b) Platform structure of multihull:

As a rule, the global transverse strength of platform ofmultihull is to be examined for all types of multihull.

1.2 Global strength calculation

1.2.1 General

The global strength of monohull and multihull are to be cal-culated as defined in [3] and [4].

1.2.2 Where a member contributing to the longitudinaland/or transversal strength is made in material other thansteel with a Young’s modulus E equal to 2,06 105 N/mm2,the steel equivalent sectional area that may be included for

the calculation of the inertia of the considered section isobtained, in m2, from the following formula:

where:

AM : Sectional area, in m2, of the member under con-sideration

E : Young modulus, in N/mm2, of the consideredmember.

1.2.3 Finite element calculationThe global strength analysis may also be examined with aFinite Elements Analysis submitted by the Designer. In thiscase, and where large openings are provided in side shelland/or in primary transverse cross structure of platform ofmultihull for windows, doors..., a special attention is to bepaid to ensure a realistic modelling of the bending andshear strength of the jambs between openings.

2 Global strength check

2.1 General

2.1.1 The global analysis check is to be successively car-ried out taking into account the scantling criteria based onmaximum stress check (see [2.2]) and on buckling check(see [2.3]).

The global analysis check is to be carried out in the follow-ing areas of the hull:

• in head sea condition (for monohull and multihull):

Along the ship from 0,25L to 0,7L from the aft end

• in quartering sea (for multihull only):

Along the float from aft to fore end, and in way of eachprimary transverse cross structure of the platform.

2.2 Maximum stress check

2.2.1 Steel and aluminium structureIt is to be checked that the actual normal stresses σA, inN/mm2, and the actual shear stresses τA, in N/mm2, calcu-lated according to [3] and, for multihull, to [4] are in com-pliance with the following criteria:

where:

σglam : Global bending permissible stress, in N/mm2, asdefined in Ch 2, Sec 3

τglam : Global shear permissible stress, in N/mm2, asdefined in Ch 2, Sec 3.

ASEE

2 06.105,----------------------AM=

σA σglam≤

τA τglam≤


NR 600, Ch 4, Sec 2

2.2.2 Composite structure

It is to be checked that the safety coefficients equal to theratio between the actual in-plane stresses σi and shearstresses τ12 in each layers in its own local axes (deducedfrom [3] and, for multihull, from [4]), and the theoreticalbreaking stresses calculated as defined in NR546 Compos-ite ships, are in compliance with the safety factors definedin Ch 2, Sec 3, [3.2.1].

2.3 Buckling check

2.3.1 Plate panel

a) Steel and aluminium plate panel:

It is to be checked that the actual normal stresses σA andshear stresses τA calculated according to [3] and, for mul-tihull, to [4] are in compliance with the following criteria:

• under simple compression:

• under double compression and shear:

• under shear:

where:

σc, τc : Critical buckling stress, in N/mm2, in com-pression and in shear as defined in App 1 forsteel plating and in NR561 AluminiumShips for aluminium plating

SF : Permissible safety coefficient defined in Ch 2,Sec 3

σc,a, σc,b : Critical buckling stresses, in N/mm2, in dou-ble compression as defined in App 1 forsteel plating and in NR561 AluminiumShips for aluminium plating

σB : Compression stress acting on side “b”, inN/mm2

b) Plate panel in composite material:

It is to be checked that the actual normal stresses σA andshear stresses τA calculated according to [3] and, formultihull, to [4] are in compliance with the followingcriteria:

where:

σc, τc, : Critical buckling stress, in N/mm2, in compres-sion and in shear in the whole panel asdefined in NR546 Composite Ships (Sec 6, [4])

SF : Permissible safety coefficient defined in Ch 2,Sec 3, [3.2.3].

2.3.2 Secondary stiffeners

As a rule, the buckling check is to be carried out for stiffen-ers parallel to the direction of compression only.

It is to be checked that the actual normal stresses σA calcu-lated according to [3] and, for multihull, to [4] is in compli-ance with the following criteria:

where:

σc : Critical buckling stress, in N/mm2, in compres-sion as defined in:

• App 1 for stiffeners in steel

• NR561 Aluminium Ships for stiffeners inaluminium

• NR546 Composite Ships for stiffeners incomposite materials

SF : Permissible safety coefficient defined in Ch 2,Sec 3.

2.3.3 Primary stiffeners

The buckling check for primary stiffeners is to be carried outas defined in [2.3.2] for secondary stiffeners.

3 Calculation of global strength for monohull ship

3.1 General

3.1.1 The calculation of the hull girder strength characteris-tics is to be carried out taking into account all the longitudi-nal continuous structural elements of the hull.

A superstructure extending over at least 0,4 L may be con-sidered as contributing to the longitudinal strength.

The transverse sectional areas of openings such as deckhatches, side shell ports, side shell and superstructure doorsand windows, in the members contributing to the longitudi-nal hull girder strength, are to be deducted from the consid-ered transverse section.

Lightening holes, draining holes and single scallops in lon-gitudinal stiffeners need not be deducted if their height isless than 0,25 hW without being greater than 75 mm, wherehW is the web height, in mm, of the considered longitudinal.

σAσc

SF------≤

σA

σc a,---------

1 9, σB

σc b,---------

1 9, τA

τc

-----1 9,

+ + 1≤

τAτc

SF------≤

σAσc

SF------≤

τAτc

SF------≤

σAσc

SF------≤


NR 600, Ch 4, Sec 2

3.2 Strength characteristics

3.2.1 Section modulusThe section modulus in any point of a transverse sectionalong the hull girder is given, in m3, by the following for-mula:

where:

IY : Moment of inertia, in m4 of the transverse sec-tion considered, calculated taking into accountall the continuous structural elements of thehull contributing to the longitudinal strength asdefined in [3.1], with respect to the horizontalneutral axis

z : Z co-ordinate, in m, of the considered point inthe transverse section above the base line

N : Z co-ordinate, in m, of the centre of gravity ofthe transverse section, above the base line.

3.2.2 Section moduli at bottom and deck

The section moduli at bottom and deck are given, in m3, bythe following formulae:

• at bottom:

• at deck:

where:

IY, N : Defined in [3.2.1]

VD : Vertical distance, in m, equal to:

VD = zD − N

zD : z co-ordinate, in m, of the deck, above the baseline.

3.2.3 Shear transverse sectionAs a rule, the total shear section SA of a transverse sectionalong the hull girder may be considered as equal to the sumof the vertical sections of the side shells and of the longitu-dinal bulkheads contributing to the global strength of thehull girder.

3.3 Overall stresses

3.3.1 Longitudinal bending stressesThe actual overall longitudinal bending stress σA in anypoint of a transverse section, in N/mm2, is obtained by thefollowing formula:

where:

MV : Vertical overall bending moment of combina-tion global loads in head sea conditions, inkN⋅m, as defined in Ch 3, Sec 2, [3]

ZA : Section modulus, in m3, calculated according to[3.2.1].

3.3.2 Vertical shear stressesThe actual vertical shear stress τA in any point of a section,in N/mm2, is obtained by the following formula:

where:

Qv : Vertical overall shear force of combination glo-bal loads in head sea conditions, in kN, asdefined in Ch 3, Sec 2, [3]

SA : Vertical section, in m2, calculated according to[3.2.3].

When deemed necessary, it may be possible to calculatethe shear stress at any point of a section as follows:

where:

Sv : Vertical section, in m2, located above the pointconsidered in the section

V : Vertical distance, in m, between the centre ofgravity of the vertical section Sv and the centreof gravity of the whole transverse section

Iy : Moment of inertia, in m4 as defined in [3.2.1]

t : Thickness, in mm, of the element where theshear stress is calculated.

4 Calculation of global strength of multihull

4.1 General

4.1.1 Type of global strength approach for multihullThe global strength of multihull is to be successively exam-ined:

• in head sea conditions, according to [3]

• in quartering sea conditions, according to [4.3]

• in addition for swath, in transverse bending moment,according to [4.4].

The global strength of multihulls having more than twofloats is to be examined on a case-by-case basis.

4.2 Global strength in head sea condition

4.2.1 GeneralThe global strength in head sea condition is to be checkedas defined in [3].

The moment of inertia IY is to be calculated for only onefloat. A platform extending in length over at least 0,4 LWL isto be considered for the calculation of the inertia of the floatwith a breadths bR and bWD as defined in Fig 1, limited to10% of the platform longitudinal length.

For swath, struts extending in length over at least 0,4 LWL isto be considered for the calculation of the inertia of thefloat.

ZAIY

z N–----------------=

ZABIY

N----=

ZADIY

VD

------=

σAMV

ZA

-------10 3–=

τAQV

SA

-------10 3–=

τAQvSvV

Iyt----------------=


NR 600, Ch 4, Sec 2

Figure 1 : Hull girder strengthAreas to be taken into account for

continuous members (plates and stiffeners)

4.3 Global strength of multihull in quartering sea and in digging in waves

4.3.1 GeneralThe global strength of multihull in quartering sea is to beexamined according to: • the present sub article for multihull built in steel material• the present sub article and NR561 Aluminium Ships for

multihull built in aluminium alloys• the present sub article and NR546 Composite Ships for

multihull built in composite materials

The global strength analysis may be carried out by a beammodel as shown in Fig 2, taking into account the bendingand shear stiffness of the primary transverse cross structureof the platform and of one float.

The transverses cross beams are fixed in the model in wayof the inner side shell of the other float.

Any other justified global analysis submitted by theDesigner may be considered.

4.3.2 Primary transverse cross structure modelEach primary transverse cross structure in the platform isconsidered as a beam in the global model, taking intoaccount:• its bending inertia about an horizontal axis (depending

mainly on the web height of the transverse cross beamor bulkhead, and the thickness of the bottom and deckplatform

• its vertical shear inertia (depending on the web height ofthe transverse cross beams or bulkheads and their thick-ness)

• its span between inner side shell of floats.

4.3.3 Float modelThe float is modelled as a beam having, as far as practicable:

• vertical and horizontal bending inertia, and

• a shear inertia, and

• a torsional inertia about longitudinal float axis

close to the actual float values.

4.3.4 Loading of the modelThe two following loading cases are to be considered:

• Loads in quartering sea condition as shown on Fig 3,where the torsional moment exerted on the platform andinduced by encountered waves in quartering sea is repre-sented by two vertical forces F defined in Ch 3, Sec 2,[5.3.2].

Note 1: As a general rule, two successive loading cases are to betaken into account: the case as shown in Fig 3 and the samecase with forces in opposite direction.

• Loads in digging in waves condition as shown on Fig 4and defined in Ch 3, Sec 2, [6.2], where the torsionalmoment induced by the digging in wave is representedby the vertical forces FVD and horizontal forces FHD

equal to the differential forces applied to each float.

4.3.5 Main structure checkThe global bending moments and shear forces distributionin the float are as shown in Fig 5, and in the primary trans-verse cross structure as shown in Fig 6.

The bending stresses σA and the shear stresses τA in the floatand in the platform of the multihull are to be directlydeduced from the beam model calculation and are to be incompliance with the criteria defined in [2].

For the primary transverse cross structure, the bendingstresses and shear stresses are to be calculated in way of themodelled float.

Particular attention is to be paid to:

• shear buckling check of cross bulkheads

• compression/bending buckling check of platform bot-tom and platform deck platings in areas where thebending moment is maximum.

Figure 2 : Model principle

��

��

CataramancenterlineLWL

Float


NR 600, Ch 4, Sec 2

Figure 3 : Primary transverse cross structure of multihull - Loading in quartering sea condition

Figure 4 : Primary transverse cross structure of multihull - Loading in digging in wave condition

Figure 5 : Overall loads in the float

��

��

��

Cataramancenterline

Float

FHD

FVD

��

��

�

�


NR 600, Ch 4, Sec 2

Figure 6 : Transverse distribution ofbending moments and shear forces

4.4 Transverse bending moment acting on twin-hull connections of swath

4.4.1 The global transversal strength analysis of the primarystructure of the platform of swath is to be carried out by adirect calculation.

The bending moment MQ, in kN.m, and the shear force FQ,in kN, applied along the platform structure of swath is to betaken equal to:

MQ = hM . FQ

where:

hM : Half the draught T, in m, plus the distance fromthe waterline at draught T to the midpoint of theplatform structure (see Ch 3, Sec 2, Fig 5)

FQ : Beam side force, in kN, defined in Ch 3, Sec 2,[6.2.2].

The bending moment distribution is to be as shown on Fig 7.The shear force is to be considered as constant along thestruts of the swath.

Figure 7 : Bending moment distribution��

��

��

��

��


NR 600, Ch 4, Sec 3

SECTION 3 LOCAL PLATING SCANTLING

Symbols

k : Material factor, defined in Ch 1, Sec 2, [2] forsteel and in Ch 1, Sec 2, [3] for aluminiumalloys

s : Length, in m, of the shorter side of the platepanel

: Length, in m, of the longer side of the platepanel

μ : Aspect ratio coefficient of the elementary platepanel, equal to:

λ : Corrosion coefficient taken equal to:

• λ = 1,15 for steel plate

• λ = 1,05 for aluminium plate

σlocam : Local permissible bending stress, in N/mm2, asdefined in Ch 2, Sec 3, in relation to the type ofload

τlocam : Local permissible shear stress, in N/mm2, asdefined in Ch 2, Sec 3, in relation to the type ofload.

1 General

1.1 General

1.1.1 The local plating scantling is to be carried outaccording to:


• for aluminium structure: the present Section and theNR561 Aluminium Ships

• for composite structure: the present Section and theNR546 Composite Ships.

1.1.2 The scantling of platings contributing to the overalllongitudinal strength of the hull girder and to the overalltransverse strength of transverse cross deck of multihull arealso to be checked as defined in Sec 2.

1.2 Local loads

1.2.1 Local load types

The local lateral pressures to be considered are:

• for bottom platings: wave loads and bottom slammingpressures (when slamming may occur for high speedship in planning hull mode)

• for side shell and, for multihull, platform bottom plat-ings: wave loads and side shell impacts

• for deck platings: wave loads, minimum loads and,when applicable, wheeled loads

• for all platings, when applicable: internal pressure.

The platings subject to compression local loads are also tobe checked against buckling criteria as defined in Sec 2,[2.3]. In this case, the value of σA considered in Sec 2, [2.3]is to be taken equal to the stress induced in the plate by thelocal loads.

1.2.2 Local load point calculation

The location of the point of the plating where the localloads are to be calculated in order to check the scantlingare defined in:

• Ch 3, Sec 1, [4.1] for steel and aluminium plates

• Ch 3, Sec 1, [4.2] for composite panels

• Ch 3, Sec 1, [4.3] for superstructure panels.

1.2.3 Theoretical scantling approach

The plating scantling under lateral pressure defined in[2.2.2] to [2.2.5] is based on an elastic scantling approach.An other approach may be considered as follows:

a) General:

When deemed necessary to the Society, the plating scant-ling may be checked at a limit state reached when plastichinges appear in the panel. In this case, the requirementsdefined in NR467 Steel Ships (dedicated for ships greaterthan 65 m in rule length) may be fully applied instead ofthe present Section, taking into account the actualstresses in the panel induced by the global hull girderbending moment and the lateral pressure.

b) Plating under Designer cargo pressure:

Plating scantling subjected to high dry cargo pressuredefined by the Designer may be checked according to[2.2.5].

2 Plating scantling

2.1 General

2.1.1 Loading cases and permissible stresses

The scantling of plating is obtained considering successivelythe different loads defined in [1.2.1] sustained by the plate(combined as defined in Ch 3, Sec 1, [3.1] if relevant), andthe associated permissible stresses defined in Ch 2, Sec 3.

μ 1= 21 1 0 33 s--

2

,+, 0 69s-- 1≤,–


NR 600, Ch 4, Sec 3

2.2 Scantling for steel and aluminium plating

2.2.1 Minimum thickness

a) As a rule, the thickness, in mm, of plates calculatedaccording to the present Section are not to be less than:

• for steel plate:

- cargo ship: 0,05 LWL k1/2 + 3,5

- non-cargo ship: 0,05 LWL k1/2 + 3,0

- sea-going launch and launch: 3,0

• for aluminium plate: 1,60 LWL1/3 k1/2

without being taken less than 4 mm or 3 mm forextruded panel,

where:

LWL : Length at waterline at full load, in m.

b) Bottom plating

As a rule, the thicknesses of bottom plating are not to belesser than the thickness of side shell.

c) Additional specific minimum thicknesses in relation tothe service notation or service feature assigned to theship are defined in Ch 5, Sec 4.

2.2.2 General caseAs a rule, the thickness of plating subjected to lateral pres-sure is to be not less than the value obtained, in mm, fromthe following formula:

where:

p : Local pressures (wave loads and pressure intanks), in kN/m2, as defined in Ch 3, Sec 3 andCh 3, Sec 4, or

Bottom impact pressure for flat bottom forwardarea, in kN/m2, as defined in Ch 3, Sec 3, [3.2],or

Bottom slamming pressure for high speed shipwith planning hull, psl, in kN/m2, as defined inCh 3, Sec 3, [3.3].

2.2.3 Plating of side shell under impact pressureAs a rule, the thickness of the side shell plating subjected toimpact pressure is to be not less than the value obtained, inmm, from the following formula:

where:

pssmin : Impact pressure on side shell and, for multihull,on platform bottom, in kN/m2, as defined in Ch3, Sec 3, [3.1.2] and/or Ch 3, Sec 3, [3.1.3]

Cf : Coefficient equal to:

- if ≤ 0,6 (1 + s):

Cf = 1

- if > 0,6 (1 + s):

Cf = (1 + s)−1/2

2.2.4 Plating subjected to wheeled loadsThe thickness of plate panels subjected to wheeled loads isto be not less than the value obtained, in mm, from the fol-lowing formula:

a) General case

where:

k : Material factor, defined in Ch 1, Sec 2, [2]for steel and in Ch 1, Sec 2, [3] for alumin-ium alloys

n : Number of wheels on the plate panel

Cm : Coefficient equal to:

• 1,00 for steel

• 1,55 for aluminium alloy

CWL : Coefficient to be taken equal to:

where /s is to be taken not greater than 3

AT : Tyre print area, in m2. In the case of doubleor triple wheels, AT is the print area of thegroup of wheels.

When the tyre print area is not known, itmay be taken equal to:

where:

QA : Axle load, in t

nW : Number of wheels for the axleconsidered

pT : Tyre pressure, in kN/m2. Whenthe tyre pressure is not indicatedby the Designer, it may be takenas defined in Tab 1

n : Number of wheels on the plate panel, takenequal to:

• 1 in the case of a single wheel

• the number of wheels in a group ofwheels in case of double or triple wheels

FW : Wheeled force, in kN, as defined in Ch 3,Sec 4, [3.3].

b) Case of vehicles with the four wheels of the axle locatedon a plate panel as shown in Fig 1

The thickness of plate panels is to be not less than thegreater value obtained, in mm, from the following for-mulae:

t = t1t = t2 (1 + β2 + β3 + β4)0,5

where:

t1 : Thickness obtained, in mm, from item a)with n = 2, considering one group of twowheels located on the plate panel

t 22 4, λμs pσlocam

--------------=

t 22 4, Cfλμs pssmin

σlocam

--------------=

t 0 9, CmCWLλ FWnk=

CWL 2 15, 0 05s--,– 0 02 4

s--–

α0 5,, 1 75α0 25,,–+=

α AT

s------=

AT 9 81nQA

nWpT

-------------,=


NR 600, Ch 4, Sec 3

t2 : Thickness obtained, in mm, from item a)with n = 1, considering one wheel locatedon the plate panel

β2, β3, β4: Coefficients obtained from the following for-mulae, replacing i by 2, 3 and 4, respec-tively (see Fig 1):

• for αi < 2:

βi = 0,8 (1,2 − 2,02 αi + 1,17 αi2 − 0,23 αi

3)

• for αi ≥ 2:

βi = 0

with αi = xi / b

xi : Distance, in m, from the wheelconsidered to the referencewheel (see Fig 1)

b : Dimension, in m, of the platepanel side perpendicular to theaxle.

Figure 1 : Four wheel axle located on a plate panel

Table 1 : Tyre pressures pT for vehicles

2.2.5 Plating under design loads given by the Designer

When the local pressure of dry cargoes given by theDesigner is three times the value defined by the presentrules in Ch 3, Sec 4, the thickness of plating, in mm, is notto be less than: • the value obtained in [2.2.2] taking into account a rule

local pressure p as defined in Ch 3, Sec 4

•

where:tc : Coefficient equal to:

• 17,2 for transversely framed plating• 14,9 for longitudinally framed plating

p : Local pressure, in kN/m2, equal to:

pDesign : Design pressure, in kN/m2, given by theDesigner

az : Vertical acceleration, in m/s2, as defined inCh 3, Sec 4, [2.2]

η : Acceleration coefficient to be taken equalto:• 1,0 for ship in displacement mode• 0,4 for ship in planing mode

R : Minimum yield stress value of the materialas defined in Ch 2, Sec 3

γ : Coefficient equal to:• 0,8 for transversely framed plating• 0,6 for longitudinally framed plating

R : Minimum yield stress value, in N/mm2, asdefined in Ch 2, Sec 3, [2.1.1].

2.3 Scantling for composite panel

2.3.1 The scantling of composite and plywood panels areto be checked according to: • the local loads defined in [1.2.1]• the safety coefficients defined in Ch 2, Sec 3, [3] for

composite and Ch 2, Sec 3, [4] for plywood, and• the calculation methodology defined in NR546 Com-

posite Ships.

Vehicle typeTyre pressure pT, in kN/m2

Pneumatic tyres Solid rubber tyres

Private cars 250 not applicable

Vans 600 not applicable

Trucks and trailers 800 not applicable

Handling machines 1100 1600

X2 X3

X4

2 1 3 4

a

b

t tcλμs 1 2P,γR-------------≡

p pDesign 1azηg---------+

=


NR 600, Ch 4, Sec 4

SECTION 4 LOCAL SECONDARY STIFFENER SCANTLING

Symbols

s : Spacing, in m, of the secondary stiffener underconsideration

: Span, in m, of the secondary stiffener underconsideration

k : Material factor, defined in Ch 1, Sec 2


τlocam : Local permissible shear stress, in N/mm2, asdefined in Ch 2, Sec 3, in relation to the type ofload

m : End stiffener condition coefficient, defined in [1.4]


• 1,20 for steel structure

• 1,05 for aluminium structure.

1 General

1.1 Local scantling

1.1.1 GeneralThe local secondary stiffener scantling is to be carried outaccording to:




1.1.2 The scantling of secondary stiffeners contributing tothe overall longitudinal strength of the hull girder and to theoverall transverse strength of platform of multihull are alsoto be checked as defined in Sec 2.

1.2 Local loads

1.2.1 Local load typesThe local lateral pressures to be considered are:

• for bottom secondary stiffeners: wave loads and bottomslamming pressures (when slamming may occur for highspeed ship in planning hull mode)

• for side shell and, for multihull, platform bottom sec-ondary stiffeners: wave loads and side shell impacts

• for deck secondary stiffeners: the greater value betweenwave loads and minimum loads, and, when applicable,wheeled loads

• for all stiffeners, when applicable: internal pressures.

The secondary stiffeners and their attached platings sub-jected to compression local loads are also to be checkedagainst buckling criteria as defined in Sec 2, [2.3]. In thiscase, the value of σA considered in Sec 2, [2.3] is to betaken equal to the stress induced in the stiffener and itsassociated plate by the local loads.

1.2.2 Local load point calculation

The location of the point of the stiffener where the localloads are to be calculated in order to check the scantlingare defined in Ch 3, Sec 1, [4].

1.3 Section modulus calculation

1.3.1 General case and attached plating

As a rule, the inertia, section modulus and shear section of sec-ondary stiffeners are to be determined by direct calculation.

The width bp, in m, of the attached plating to take intoaccount for the inertia and section modulus calculations areto be taken equal to the spacing between stiffeners, or halfof the spacing between stiffeners when the plating extendson one side only, without being taken greater than 0,2 (or0,1 when the plating extends on one side only), where isthe length of the primary stiffener.

Note 1: For secondary stiffeners on sandwich plating, the limitationequal to 0,2 or 0,1 is not to be taken into account.

1.3.2 Bulb section for steel stiffeners

As a rule, the inertia, section modulus and shear section ofbulb section of steel stiffener may to be determined takinginto account the following equivalent dimensions of anangle profile:

where:

h’w, t’w : Height and net thickness of the bulb section, in

mm, as shown in Fig 1

α : Coefficient equal to:

hw hw′ hw

′

9 2,-------- 2+–=

tw tw′=

bf α tw′ hw

′

6 7,-------- 2–+=

tfhw

′

9 2,-------- 2–=

1 1, 120 hw′–( )2

3000-----------------------------+ for hw

′ 120≤

1 0, for hw′ 120>


NR 600, Ch 4, Sec 4

Figure 1 : Dimension of a steel bulb section

1.3.3 Bulb section for aluminium stiffeners

For aluminium secondary stiffeners, the equivalent dimensionsof an angle bar are as defined in [1.3.2] are not applicable.

The dimensions of the bulb section are to be specified bythe Shipyard.

1.3.4 Stiffeners in composite materials

The inertia, section modulus and shear section of secondarystiffeners in composite materials are to be determined asdefined in the NR546 Composite Ships.

1.4 End stiffener conditions for section moduli calculation

1.4.1 The connection of secondary stiffeners with sur-rounding supporting structure is to be taken into account inthe calculation of the rule stiffener section moduli.

The following three assumptions on end stiffener conditionsare taken into consideration in the scantling formulae, usinga coefficient m equal, successively, to:

• for fixed end condition: m = 12

The cross-section at the ends of the stiffener cannotrotate under the effect of the lateral loads (as a rule, thesecondary stiffeners are considered with fixed ends).

The section modulus is to be checked at the ends of thestiffener.

• for simply supported end condition: m = 8

The cross-section at the ends of the stiffener can rotatefreely under the effect of the lateral loads.

The section modulus is to be checked at mid span of thestiffener.

• for intermediate conditions: m = 10

The cross-section at the ends of the stiffener is in anintermediate condition between fixed end conditionand simply supported end condition.

The section modulus is to be checked at mid span of thestiffener.

1.5 Span of stiffener

1.5.1 The span of the stiffeners considered in the scant-ling formulae is to be measured as shown in Fig 2 to Fig 4.

1.5.2 For open floors, when a direct beam calculation tak-ing into account all the elements of the open floor is notcarried out, the span of the upper and lower secondarystiffeners connected by one or two strut(s) is to be takenequal to 0,7 2 instead of 1 (see Fig 5).

Figure 2 : Stiffener without brackets

Figure 3 : Stiffener with a stiffener at one end

Figure 4 : Stiffener with a bracket and a stiffenerat one end

Figure 5 : Span of stiffeners in case of open floors

��

��

�

�

�

�1

�2


NR 600, Ch 4, Sec 4

2 Secondary stiffener scantling

2.1 General

2.1.1 Loading cases and permissible stresses

The scantling of secondary stiffener is obtained consideringsuccessively the different loads sustained by the stiffenerdefined in [1.2.1] (combined as defined in Ch 3, Sec 1, [3.1]if relevant) and the permissible stresses defined in Ch 2, Sec 3.

2.1.2 Weld section of secondary stiffener

Where no stiffener brackets are provided at the connectionbetween the secondary stiffener and the primary supportingelement, the resistant weld section Aw, in cm2, is not to beless than twice the value of Ash defined in [2.2].

2.2 Scantling for steel and aluminium secondary stiffener

2.2.1 General

a) Minimum section modulus:

As a rule, the minimum section modulus, in cm3, of sec-ondary stiffener calculated according to the present Sec-tion are not to be less than:

• for steel secondary stiffener: 0,2 LWL k + 4

• for aluminium secondary stiffener: 2 LWL1/3 k

where:


k : Material factor defined in Ch 1, Sec 2.

b) Welding between secondary stiffener and primary struc-ture:

As a rule, the resistant weld section of the fillet weldconnecting the secondary stiffener to the primary struc-ture is to be as defined in:

• Ch 6, Sec 2, [2.6.7] for steel structure

• NR561 Aluminium Ships, Sec 3 for aluminiumstructure.

2.2.2 General case

As a rule, the section modulus Z, in cm3, and the shear areaAsh, in cm2, of the secondary stiffeners subjected to laterallocal pressures are to be not less than the values obtainedfrom the following formulae:

• for horizontal stiffeners (longitudinal or transverse):

where:

p : Local pressures (wave loads and pressure intanks), in kN/m2, as defined in Ch 3, Sec 3and Ch 3, Sec 4, or

Bottom impact pressure for flat bottom forwardarea, in kN/m2, as defined in Ch 3, Sec 3,[3.2], or

Bottom slamming pressure for high speedship with planning hull, psl, in kN/m2, asdefined in Ch 3, Sec 3, [3.3]

Ct : Reduction coefficient defined as follows:

• for vertical transverse stiffeners:

where:

p1, p2 : Equivalent pressure, in kN/m2, as defined inTab 1

m1, m2 : End stiffener condition coefficients definedin Tab 1

Ct : As defined above.

Table 1 : Equivalent pressures

2.2.3 Secondary stiffeners under side shell impactsAs a rule, the section modulus Z, in cm3, and the shear areaAsh, in cm2, of the horizontal and vertical secondary stiffen-ers sustaining lateral side shell impacts are to be not lessthan the values obtained from the following formulae:

where:

pssmin : Impact pressure on side shell and, for multihull,on platform bottom, in kN/m2, as defined in Ch3, Sec 3, [3.1.2] and/or Ch 3, Sec 3, [3.1.3]

Cf, Ct : Reduction coefficients equal to:

Cf = 0,3 (3 2 − 0,36) / 3 with ≥ 0,6 m

Ct = 0,6 / without being taken greater than 1.

Z 1000λ ps2

mσlocam

-------------------=

Ash 5λCtps

τlocam

-------------=

End stiffener condition P1 m1 P2 m2

Both ends fixed2 pSupper +3 pSlower

603 pSupper +7 pSlower

20

Lower end fixed, upper end supported



40

Both ends supportedpSupper +pSlower

16pSupper +2 pSlower

6

Note 1:psupper, pslower : Sea pressure or internal pressure as defined in

Ch 3, Sec 3 or Ch 3, Sec 4, in kN/m2, at lower andupper calculation point of the vertical stiffener.

Ct 1 s2------–=

Z 1000λ p1s2

m1σlocam

---------------------=

Ash 1000λCtp2s

m2τlocam

---------------------=

Z 1000λCfPssmins2

mσlocam

---------------------=

Ash 5λCtPssminsτlocam

-------------------=


NR 600, Ch 4, Sec 4

2.2.4 Secondary stiffeners under wheeled loadsAs a rule, the secondary stiffeners scantling under wheeledloads are checked by direct calculation. Single span andmulti span stiffeners are considered.

The values of the bending stresses σ and shear stresses τ, inN/mm2, calculated according to the following approaches areto be less than the permissible stresses defined in Ch 2, Sec 3.

Table 2 : Wheeled loads - Coefficient αW

Table 3 : Wheeled loads - Coefficients KS and KT

a) Single span stiffeners

The maximum normal stress σ and shear stress τ are tobe obtained, in N/mm2, from the following formulae:

where:

Za, Asha : Actual section modulus, in cm3, and shearsection, in cm2, of the stiffener considered

FW : Wheeled force, in kN, as defined in Ch 3,Sec 4, [3.3]

αw : Coefficient taking into account the numberof wheels per axle considered as acting onthe stiffener, defined in Tab 2

KS, KT : Coefficients taking into account the numberof axles considered as acting on the stiff-ener, defined in Tab 3.

b) Multi span stiffeners

The maximum normal stress σ and shear stress τ are tobe obtained by a direct calculation taking into account:

• the distribution of wheeled loads applying on thestiffener

• the number and position of intermediate supports(girders, bulkheads, etc.)

• the condition of fixity at the ends of the stiffener andat intermediate supports

• the geometrical characteristics of the stiffener on theintermediate spans.

2.2.5 Struts for open floors

As a general rule, the scantling of the struts is to be checkedby direct calculation, taking into account the compressionand/or the tensile force Q, in kN, calculated as follows:

• compression force:

• tensile force:

where:

PBottom : Local loads (wave loads and/or dynamic loads),in kN/m2, applied on the ship bottom, as definedin Ch 3, Sec 3

PDBottom : Local loads, in kN/m2, applied on the ship dou-ble bottom, as defined in Ch 3, Sec 4

PBallast : Ballast local loads at mid-height of the shipdouble bottom, in kN/m2, as defined in Ch 3,Sec 4

2 : Span of the upper and lower secondary stiffen-ers, as defined in Fig 5.

When deemed necessary by the Society, the buckling checkof struts may be examined on a case-by-case basis.

Configuration αW

Single wheel

1

Double wheels

Triple wheels

Note 1:y : Distance, in m, from the external wheel of a group

of wheels to the stiffener under consideration, tobe taken equal to the distance from the externalwheel to the centre of the group of wheels.

CoefficientConfiguration

Single axle Double axles

KS 1

•

•

KT 1

Note 1:d : Distance, in m, between the two axles : Span, in m, of the secondary stiffener under con-

sideration

y

s

2 1 ys---–

s

y

3 2ys---–

if d 3⁄≤

17281---------- 4d

3-------– d2

2-----– d4

4-----+

if d 3⁄>

43--- 4d

3-------– 3d2

2

--------- 8d3

33---------–+

2 d2------– 3d2

22---------– d3

3-----+

σ αWKSFW

6Za

---------103=

τ αWKT10FW

ASha

-------------=

Qcs2

4------- PBottom PDBottom+( )=

Qt2s2PBallast

4---------------------------=


NR 600, Ch 4, Sec 4

2.2.6 Secondary stiffener check taking into account the overall bending stress

When deemed necessary, the value of the section modulusZ, in cm3, may be calculated as follows, instead of the valuedefined in [2.2.2]:

considering the following lateral local pressure cases:

• wave loads

• internal pressures,

where:

σad : Local permissible bending stress, in N/mm2, tobe taken equal to R − 1,25 σX1

R : Minimum yield stress value, in N/mm2, asdefined in Ch 2, Sec 3, [2.1.1]

σX1 : Overall longitudinal bending stress, in kN/m2,calculated as defined in Sec 2, [3.3.1], to betaken not less than 20 N/mm2.

2.3 Scantling of secondary stiffeners in composite materials

2.3.1 The scantling of composite and plywood stiffenersare to be checked according to: • the local loads defined in [2.1.1]• the safety coefficients defined in Ch 2, Sec 3, [3] for

composite and Ch 2, Sec 3, [4] for plywood, and• the calculation methodology defined in NR546 Com-

posite Ships.

Z 1000λ ps2

mσad

-------------=


NR 600, Ch 4, Sec 5

SECTION 5 LOCAL PRIMARY STIFFENER SCANTLING

Symbols

s : Spacing, in m, of the primary stiffener underconsideration

: Span, in m, of the primary stiffener under con-sideration

k : Material factor, defined in Ch 1, Sec 2


τlocam : Local permissible shear stress, in N/mm2, asdefined in Ch 2, Sec 3, in relation to the type ofload

p : Local loads (wave loads, dynamic loads andpressure in tanks), in kN/m2, as defined in Ch 3,Sec 3 and/or Ch 3, Sec 4


• 1,20 for steel structure

• 1,05 for aluminium structure.

1 General

1.1 Local scantling

1.1.1 The local primary stiffener scantling is to be carriedout according to:




1.1.2 The scantling of primary stiffeners contributing to theoverall longitudinal strength of the hull girder and to theoverall transverse strength of platform of multihull are alsoto be checked as defined in Sec 2.

1.2 Structural beam models

1.2.1 Isolated beam model

a) The requirements for the scantling of primary stiffenersdefined in the present Section apply for isolated beamcalculation.

b) Local loads

The local lateral pressures to be considered are definedin [1.2.2], b).

c) Local load point calculation

The location of the point of the stiffener where the localloads are to be calculated in order to check the scant-ling are defined in Ch 3, Sec 1, [4].

d) The scantling of primary stiffeners and their attachedplatings subjected to compression local loads are also tobe checked against buckling criteria as defined in Sec 2,[2.3]. In this case, the value of σA considered in Sec 2,[2.3] is to be taken equal to the stress induced in thestiffener and its associated plate by the local loads.

e) Checking criteria

The bending stresses, shear stresses and combinedstresses calculated by the model are to be in accordancewith the permissible values defined in Ch 2, Sec 3.

1.2.2 Two- or three-dimensional beam modelWhen an isolated beam calculation of the primary structureis not possible due to an interaction of the primary stiffen-ers, a two- or three-dimensional structural model analysisincluding the different primary stiffeners is to be carried outas follows:

a) Model

The structural model is to represent the primary support-ing members, with their attached plating (as defined in[1.4.1]), of the structure area considered.

The extension of the structural model is to be such thatthe results in the areas to be analysed are not influencedby the unavoidable inaccuracy in the modelling of theboundary conditions.

b) Loading conditions

The local lateral pressures to be considered are:

• for bottom primary stiffeners: wave loads and bottomslamming pressures (when slamming may occur)

• for side shell and, for multihull, primary transversecross structure of platform bottom: wave loads (with-out taking into account side shell impact)

• for deck primary stiffeners: wave loads, minimumloads and, when applicable, wheeled loads

• for all primary stiffeners, when applicable: internalpressures.

When deemed necessary, it may be taken into account ofthe counteraction between the internal and external loadsin the most severe conditions (see Ch 3, Sec 1, [3.1.1]).

Note 1: When a bottom slamming pressure analysis is carried outfor high speed ship in planing hull mode, the impact pressurepsl defined in Ch 3, Sec 3, [3.3.2] is to be only applied on onefloor of the model as a constant pressure. The other floors ofthe model are to be loaded by the bottom sea pressure definedin Ch 3, Sec 3, [2.2.1].


NR 600, Ch 4, Sec 5

c) Local load point calculation

The location of the point of the stiffener where the localloads are to be calculated in order to check the scant-ling are defined in Ch 3, Sec 1, [4].

d) Checking criteria

The bending stresses, shear stresses and combinedstresses calculated by the model are to be in accordancewith the permissible values defined in Ch 2, Sec 3.

1.2.3 Curved beam model

The curvature of primary supporting members may be takeninto account by direct analysis.

In case of two dimensional or three dimensional beamstructural model, the curved primary supporting membersmay be represented by a number N of straight beams, Nbeing adequately selected to minimize the spring effect inway of knuckles.

The stiffness of knuckle equivalent springs is considered asminor from the point of view of the local bending momentand the shear force distribution when the angle betweentwo successive beams is not more than 3°.

1.3 Finite element model

1.3.1 General

When the analysis of primary stiffener structure is carriedout by a finite element model, the model is to be submittedto the Society for examination.

As a rule, one of the procedure defined in NR467 SteelShips, Pt B, Ch 7, App 1 is to be adopted for the finite ele-ment model.

1.4 Beam section modulus calculation

1.4.1 Attached plating

As a rule, the inertia, section modulus and shear section ofprimary stiffeners are to be determined by direct calculation.

The width bp, in m, of the attached plating to take intoaccount for the inertia and section modulus calculations areto be taken equal to the spacing between primary stiffeners(or half of the spacing between primary stiffeners when theplating extends on one side only), without being takengreater than 0,2 (or 0,1 when the plating extends on oneside only), where is the length of the primary stiffener.

1.5 End stiffener conditions for calculation

1.5.1 Definition and calculation conditions

The assumptions on end stiffener conditions for the calcula-tion of section moduli of primary stiffeners are defined inSec 4, [1.4.1].

As a rule, the coefficient m is to be taken equal to 10 for anisolated beam calculation of primary stiffener.

2 Primary stiffener scantling

2.1 Scantling for steel and aluminium primary stiffeners under lateral loads

2.1.1 Scantling

The local primary stiffener scantling is to be carried out asdefined for the secondary stiffener scantling in Sec 4,excepted otherwise specified, considering successively thedifferent loads sustained by the primary stiffener defined in[1.2.1], b) or [1.2.2], b) and the relevant permissible stressesdefined in Ch 2, Sec 3.

When the local primary scantling is checked according toSec 4, [2.2.6], the local permissible stresses σad, in N/mm2,is to be taken equal to 0,9 (R − 1,4 σX1).

The minimum section modulus for secondary stiffenersdefined in Sec 4, [2.2.1] is not applicable to primary stiffen-ers.

2.1.2 Additional check of primary stiffeners

In addition to [2.1.1], the primary stiffeners are also to beexamined taking into account the following requirements:

a) Buckling of attached plating

Depending on the compression stress level in theattached plating induced by the bending of primary stiff-ener under the local loading cases, it may be necessaryto check the buckling of the attached plating along theprimary stiffener span.

The buckling of the attached plating is to be checked asindicated in Sec 2, [2.3].

b) Minimum web thickness

As a rule, the thickness of the web, in mm, for steel andaluminium structure is to be not less than:

Additional specific minimum thicknesses of webs inrelation to the service notation or service featureassigned to the ship are defined in Ch 5, Sec 4.

2.2 Scantling for steel and aluminium primary stiffeners under wheeled loads

2.2.1 Wheeled loads

For primary supporting members subjected to wheeledloads, the section modulus and shear area may be calcu-lated as defined for secondary stiffener in Sec 4, [2.2.4],considering the distribution of the wheeled loads as an uni-form pressures p.

This uniform pressure is to be equivalent to the distributionof vertical wheeled concentrated forces when such forcesare closely located and is to be determined in the mostunfavourable case, i.e. where the maximum number ofaxles are located on the same primary supporting member,according to Fig 1 and to Fig 2.

t 1 2 3 7, 0 015L,+( ),=


NR 600, Ch 4, Sec 5

Figure 1 : Distribution of vehicles on a primary supporting member

Figure 2 : Distance between axles of two consecutive vehicles

The uniform pressure p, in kN/m2, is to be calculated as fol-lows:

where:

peq : pressure equivalent to the vertical wheel distri-bution, in kN/m2 to be taken equal to:

nV : Maximum number of vehicles possible locatedon the primary supporting member

QA : Maximum axle load, in t, as defined in Ch 3,Sec 4, [3.3.1]

X1 : Minimum distance, in m, between two consec-utive axles (see Fig 2)

X2 : Minimum distance, in m, between axles of twoconsecutive vehicles (see Fig 2)

az : Vertical acceleration, in m/s2, as defined in Ch3, Sec 4, [2.2]

g : Gravity acceleration taken equal to 9,81 m/s2

α : Coefficient taken equal to:

• 0,5 in general

• 1,0 for landing gears of trailers

η : Acceleration coefficient to be taken equal to:

• 1,0 for ship in displacement mode

• 0,4 for ship in planing mode.

2.3 Primary stiffeners in composite materials

2.3.1 The scantling of composite and plywood stiffenersare to be checked according to:

• the local loads defined in [1.2.1], b) or [1.2.2], b)

• the calculation methodology defined in NR546 Com-posite Ships

• the safety coefficient defined in Ch 2, Sec 3, [3] forcomposite and Ch 2, Sec 3, [4] for plywood.

2.3.2 Two- or three-dimensional structural model

When a two- or three-dimensional structural model is pro-vided, the primary structure check is to be carried out asdefined in [1.2.2] and in NR546 Composite Ships.

3 Specific requirements

3.1 General

3.1.1 Material

The specific requirements defined in the present article areapplicable to primary stiffeners made in steel.

Primary stiffeners made in aluminium are to be in accord-ance with the NR561 Aluminium Ships.

Primary stiffeners made in composite are to be in accord-ance with the NR546 Composite Ships.

3.2 Cut-outs and large openings

3.2.1 Cut-outs in web

Cut-outs for the passage of secondary stiffeners are to be assmall as possible and well rounded with smooth edges.

In general, the height of cut-outs is to be not greater than50% of the height of the primary supporting member.

3.2.2 Location of cut-out in web

As a general rules, where openings such as lightening holesor duct routing for pipes, electrical cable,..., are cut in pri-mary supporting members, they are to be equidistant fromthe face plate and the attached plate. As a rule, their heightis not to be more than 20% of the primary supporting mem-ber web height.

The length of the openings is to be not greater than:

• at the end of primary member span: 25% of the distancebetween adjacent openings

• elsewhere: the distance between adjacent openings.

Openings may not be fitted in way of toes of end brackets.

3.2.3 Large openings

In case of large openings as shown in Fig 3, the secondarystresses in primary supporting members are to be consid-ered for the reinforcement of the openings, where deemednecessary.

The secondary stresses may be calculated in accordancewith the following procedure:

�

X1 X2S

p peq 1 αazηg---------+

=

peq 10nVQA

s-------------- 3

X1 X2+s

------------------– =


NR 600, Ch 4, Sec 5

• Members (1) and (2) are subjected to the followingforces, moments and stresses:

where:MA, MB : Bending moments, in kN.m, in sections A

and B of the primary supporting memberm1, m2 : Bending moments, in kN.m, in (1) and (2)d : Distance, in m, between the neutral axes of

(1) and (2)σF1, σF2 : Axial stresses, in N/mm2, in (1) and (2)σm1, σm2 : Bending stresses, in N/mm2, in (1) and (2)QT : Shear force, in kN, equal to QA or QB,

whichever is greaterτ1, τ2 : Shear stresses, in N/mm2, in (1) and (2)w1, w2 : Net section moduli, in cm3, of (1) and (2)S1, S2 : Net sectional areas, in cm2, of (1) and (2)Sw1, Sw2 : Net sectional areas, in cm2, of webs in (1)

and (2)I1, I2 : Net moments of inertia, in cm4, of (1) and

(2) with attached plating

• The combined stress σC calculated at the ends of members(1) and (2) is to be obtained from the following formula:

• The combined stress σC is to comply with the checkingcriteria in Ch 2, Sec 3. Where these checking criteria arenot complied with, the cut-out is to be reinforced accord-ing to one of the solutions shown from Fig 4 to Fig 6:- continuous face plate (solution 1): see Fig 4- straight face plate (solution 2): see Fig 5- compensation of the opening (solution 3) by increase

of the web thickness t1: see Fig 6.

Other arrangements may be accepted provided they aresupported by direct calculations submitted to the Soci-ety for review.

Figure 3 : Large openings in primary supporting members - Secondary stresses

Figure 4 : Stiffening of large openings in primary supporting members - Solution 1



FMA MB+

2d----------------------=

m1MA MB–

2--------------------- K1=

m2MA MB–

2--------------------- K2=

σF1 10 FS1

-----=

σF2 10 FS2

-----=

σm1m1

w1

-------103=

σm2m2

w2

-------103=

τ1 10K1QT

Sw1

-------------=

τ2 10K2QT

Sw2

-------------=

K1I1

I1 I2+--------------=

K2I2

I1 I2+--------------=

σc σF σm+( )2 3τ2+=

MA

MMBQA

Q QB

R/2

1

2 BA

R

2

1

d

FK2 QT

- F

K1 QT

m2

m1

0,5 H1,5 H

H

t1 t

H

H


NR 600, Ch 4, Sec 5

3.3 Web stiffening arrangement for primary supporting members

3.3.1 Webs of primary supporting members are generallyto be stiffened where their height, in mm, is greater than100 t, where t is the web thickness, in mm, of the primarysupporting member.

In general, the web stiffeners of primary supporting mem-bers are to be spaced, in mm, not more than 110 t.

3.3.2 The section modulus of web stiffeners of non-water-tight primary supporting members is to be not less than thevalue obtained, in cm3, from the following formula:

where:

s : Length, in m, of web stiffeners

t : Web thickness, in mm, of the primary support-ing member

Ss : Spacing, in m, of web stiffeners.

Moreover, web stiffeners located in areas subject to com-pression stresses are to be checked in buckling condition.

3.3.3 As a general rule, tripping brackets (see Fig 7) weldedto the face plate are generally to be fitted:

• every fourth spacing of secondary stiffeners

• at the toe of end brackets

• at rounded face plates

• in way of cross ties

• in way of concentrated loads.

Where the width of the symmetrical face plate is greaterthan 400 mm, backing brackets are to be fitted in way of thetripping brackets.

3.3.4 The arm length d of tripping brackets is to be not lessthan the greater of the following values, in m:

where:b : Height, in m, of tripping brackets, shown in Fig 7st : Spacing, in m, of tripping bracketst : Thickness, in mm, of tripping brackets.

3.3.5 Steel tripping brackets with a thickness, in mm, lessthan 16,5 times the length, in m, of the free edge of thebracket are to be flanged or stiffened by a welded faceplate.

The sectional area, in cm2, of the flanged edge or the faceplate is to be not less than 10 times the length, in m, of thefree edge of the bracket.

Figure 7 : Primary supporting member: Web stiffener in way of secondary stiffener

w 2 5s2tSs2,=

d 0 38b,=

d 0 85b st

t---,=

b

dδ


NR 600, Ch 4, Sec 6

SECTION 6 STIFFENER BRACKETS SCANTLING AND STIFFENER

END CONNECTIONS

1 General arrangement of brackets

1.1 Materials

1.1.1 The requirements of the present Section are applica-ble to hull made totally or partly in steel.

For ship hulls built in aluminium alloys, the requirements toapply are defined in NR561 Aluminium Ships, Section 6.

For ship hulls built in composite materials, the requirementsto apply are defined in NR546 Composite Ships.

1.2 General requirements

1.2.1 As a general rules, brackets are to be provided at thestiffener ends when the continuity of the web and the flangeof the stiffeners is not ensured in way of their supports.

1.2.2 Arm of end brackets are to be of the same length, asfar as practicable.

1.2.3 The section of the end bracket web is generally to benot less than that of the supported stiffener.

1.2.4 The section modulus of the end bracket is to be atleast equal to the section modulus of the stiffener supportedby the bracket.

When the bracket is flanged, the section modulus is to beexamined in way of flange as well as in way of the end ofthe flange.

1.2.5 Bracket flangesSteel brackets having a thickness, in mm, less than 16,5 Lb areto be flanged or stiffened by a welded face plate, such that:

• the sectional area, in cm2, of the flanged edge or theface plate is at least equal to 10 Lb

• the thickness of the bracket flange is not less than that ofthe bracket web,

where:

Lb : length, in m, of the free edge of the bracket.

1.2.6 When a face plate is welded on end brackets to bestrengthened, this face plate is to be symmetrical.

In such a case, the following arrangements are to be com-plied with, as a rule:

• the face plates are to be snipped at the ends, with totalangle not greater than 30°

• the width of the face plates at ends is not to exceed 25 mm

• the face plates being 20 mm thick or above are to betapered at ends over half the thickness

• the radius of the curved face plate is to be as large aspossible

• a collar plate is to be fitted in way of bracket toes

• the fillet weld throat thickness is to be not less than t/2,where t is the thickness at the bracket toe.

2 Bracket for connection of perpendicular stiffeners


2.1.1 Typical bracket for connection of perpendicular stiff-eners are shown from Fig 1 to Fig 6.

As a general rules, brackets are to be in accordance with therequirements defined in [1.2].

Where no direct calculation is carried out, the minimumlength d, in mm, as defined from Fig 1 to Fig 6 may be takenequal to:

where:

ϕ : Coefficient equal to:

• for unflanged brackets:

ϕ = 48,0

• for flanged brackets:

ϕ = 43,5

w : Required section modulus of the supported stiff-ener, in cm3

t : Bracket thickness, in mm.

Figure 1 : Bracket at upper end of secondary stiffener on plane bulkhead

d ϕ w 30+t

-----------------=

d

d

hs


NR 600, Ch 4, Sec 6

Figure 2 : Bracket at lower end of secondary stiffener on plane bulkhead

Figure 3 : Other bracket arrangement at lower end of secondary stiffeners on plane bulkhead

Figure 4 : Connections of perpendicular stiffeners in the same plane

Figure 5 : Connections of stiffeners located in perpendicular planes

Figure 6 : Lower brackets of main frames

2.1.2 When a bracket is provided to ensure the simultane-ous continuity of two (or three) stiffeners of equivalent stiff-ness, the bracket scantling is to be determined by directcalculation, taking into account the balanced bendingmoment in the connection of the two (or three) stiffeners.

3 Bracket ensuring continuity of secondary stiffeners

3.1 General

3.1.1 Where secondary stiffeners are cut in way of primarysupporting members, brackets are to be fitted to ensure thestructural continuity as defined in Fig 7, or equivalent. Theirsection moduli and their sectional area are to be not lessthan those of the secondary stiffeners.

The bracket thickness is to be not less than that of the sec-ondary stiffeners and dimension d of each bracket is to beas a rule not less than 1,5 hS.

Equivalent arrangement may be considered on a case-by-case basis.

Figure 7 : End connection of secondary stiffener Backing bracket

d

d

hs

A

A

Section A-A

d

hs

d

d

hs

dhs

d d

hs


NR 600, Ch 4, Sec 6

4 Bracketless end stiffeners connections

4.1 Bracketless end connections

4.1.1 Case of two stiffeners

In the case of bracketless crossing between two primarysupporting members (see Fig 8), the thickness tb of the com-mon part of the webs, in mm, is to be not less than thegreater value obtained from the following formulae:

where:

Sf1, Sf2 : Flange sections, in mm2,of member 1 and mem-ber 2 respectively

σ1, σ2 : Normal stresses, in N/mm2, in member 1 andmember 2 respectively

Ry : Minimum guaranteed yield stress, in N/mm2.

Figure 8 : Bracketless end connections between two primary supporting members

4.1.2 Case of three stiffeners

In the case of bracketless crossing between three primarysupporting members (see Fig 9), and when the flange conti-nuity is ensured between member 2 and member 3, thethickness tb of the common part of the webs, in mm, is to benot less than:

When the flanges of member 2 and member 3 are not con-tinuous, the thickness of the common part of the webs is tobe defined as [4.1.1].

Figure 9 : Bracketless end connections between three primary supporting members

4.1.3 Stiffening of common part of webs

When the minimum value of heights h1 and h2 of the mem-ber 1 and member 2 is greater than 100 tb , the commonpart of the webs is generally to be stiffened.

4.1.4 Lamellar tearing in way of flanges

When lamellar tearing of flanges is likely to occur, a 100%ultrasonic testing of the flanges in way of the weld may berequired after welding.

4.2 Other type of end connection

4.2.1 Where end connections are made according to Fig 10,a stiffener with sniped ends is to be fitted on connection web,when:

a > 100 t

where:

a : Dimension, in mm, measured as shown on Fig 10

t : Web thickness, in mm.

Figure 10 : End connection with stiffener

tbSf1σ1

0 5h2ReH,------------------------=

tbSf2σ2

0 5h1ReH,------------------------=

tb max t1 t2,( )=

Member 2

Member 1

h1tb

h2

tbSf1σ1

0 5h2Ry,---------------------=

Member 2

Member 1

Member 3

h1tb

h2

�

�

��

�


NR 600, Ch 4, Sec 7

SECTION 7 PILLAR SCANTLING

Symbols

A : Cross-sectional area, in cm2, of the pillar

I : Minimum moment of inertia, in cm4, of the pil-lar in relation to its principal axis

E : Young’s modulus, in N/mm2, to be taken equal to:

• for steels in general:

E = 2,06⋅105 N/mm2

• for stainless steels:

E = 1,95⋅105 N/mm2

: Span, in m, of the pillar

f : Fixity coefficient, to be obtained from Tab 1

r : Minimum radius of giration, in cm, equal to:

ReH : Minimum guaranteed yield stress, in N/mm2

σCB : Global pillar buckling stress, in N/mm2

σCL : Local pillar buckling stress, in N/mm2.

1 General

1.1 Materials

1.1.1 The requirements of the present Section are applica-ble to pillars built of:• steel: as defined in [2]• aluminium: as defined in [3]• composite materials: as defined in [4].

1.2 Application

1.2.1 The requirements of this Section deals with the buck-ling check of independent profiles pillars or bulkheads stiff-eners acting as pillar.The general requirements relating to pillars arrangement aregiven in Ch 2, Sec 1, [5.4].

1.2.2 Calculation approachThe pillar buckling stresses σCB and σCL , in N/mm2, and themaximal allowable axial load PC , in kN, are to be succes-sively examined according to the two following methods: • global column buckling, and• local buckling.

Table 1 : Coefficient f

r IA----=

Conditions of fixity

f 0,5 (1) 0,7 1,0 2,0 1,0 2,0

(1) End clamped condition may only be considered when the structure in way of pillar ends can not rotate under the effect of loadings.


NR 600, Ch 4, Sec 7

1.2.3 Actual compression axial loadWhere pillars are aligned, the compression axial load FA , inkN, is equal to the sum of the loads supported by the pillarconsidered and those supported by the pillars locatedabove, multiplied by a weighting factor r.

The load factor depends on the relative position of each pil-lar with respect to that considered (i.e the number of tiersseparating the two pillars).

The compression axial load in the pillar is to be obtained, inkN, from the following formula:

where:

AD : Area, in m2, of the portion of the deck or theplatform supported by the pillar considered

ps : Pressure on deck, in kN/m2, as defined in Ch 3,Sec 4

pL : Local load on deck, in kN, if any Ch 3, Sec 4

r : Load factor depending on the relative positionof each pillar above the one considered, to betaken equal to:

• r = 0,9 for the pillar immediately above thepillar considered

• r = 0,9i > 0,478 for the ith pillar of the lineabove the pillar considered

Qi : Vertical local load, in kN, supported by the ith

pillar of the line above the pillar considered, ifany.

2 Pillar in steel material

2.1 Buckling of pillars subjected to compression axial load

2.1.1 Global critical column buckling stressThe global critical column buckling stress of pillars σCB is tobe obtained, in N/mm2, from the following formulae:

where:

σE : Euler pillar buckling stress, in N/mm2, to beobtained from the following formula:

2.1.2 Local critical buckling stress The local critical buckling stress of pillars σCL is to beobtained, in N/mm2, from the following formulae:

where:

σEi : Euler local buckling stress, in N/mm2, to betaken equal to the values obtained from the fol-lowing formulae:

• For circular tubular pillars:

where:

t : Pillar thickness, in mm

D : Pillar outer diameter, in mm

• For rectangular tubular pillars:

where:

b : Greatest dimension of the cross-section, in mm

t : Plating thickness in relation to b,in mm

• For built up pillars, the lesser of:

where:

hW : Web height of built-up section,in mm

tW : Web thickness of built-up sec-tion, in mm

bF : Face plate width of built-up sec-tion, in mm

tF : Face plate thickness of built-upsection, in mm.

2.1.3 Maximum allowable axial loadThe maximum allowable axial load PC , in kN, is the smallerof the two following values:

2.2 Buckling of pillars subjected to compression axial load and bending moments

2.2.1 Checking criteriaIn addition to the requirements in [2.1], the scantling of thepillar loaded by the compression axial load and bendingmoments are to comply with the following formula:

where:

F : Actual compression load, in kN, acting on thepillar

A : Cross-sectional area, in cm2, of the pillar

FA ADps pL ri

Qi+ +=

σCB σE for σEReH

2--------≤=

σCB ReH 1ReH

4σE

---------– for σE

ReH

2-------->=

σE π2E IA f( )2----------------10 4–=

σCL σEi for σEiReH

2--------≤=

σCL ReH 1ReH

4σEi

----------– for σEi

ReH

2-------->=

σEi 12 5 E206000-------------------- t

D---- 104,=

σEi 78 E206000-------------------- t

b---

2

104=

σEi 78 E206000-------------------- tW

hW

-------

2

104=

σEi 32 E206000-------------------- tF

bF

-----

2

104=

PCσCB

1 35,-------------A 10 1–⋅=

PC σCLA 10 1–⋅=

10F 1A---- Φe

wP

--------+ 103Mmax

wP

------------ + 0 85ReH,≤


NR 600, Ch 4, Sec 7

e : Eccentricity, in cm, of the compression loadwith respect to the centre of gravity of the cross-section

σE : Euler column buckling stress, in N/mm2,defined in [2.1.1]

wP : Minimum section modulus, in cm3, of the cross-section of the pillar

Mmax : Max (M1, M2, M0)

M1 : Bending moment, in kN.m, at the upper end ofthe pillar

M2 : Bending moment, in kN.m, at the lower end ofthe pillar

provided that:

2.3 Vertical bulkhead stiffener acting as pillar

2.3.1 When a vertical stiffening member is fitted on thebulkhead in line with the deck primary supporting membertransferring the loads from the deck to the bulkhead (as apillar), this vertical stiffener is to be calculated as defined in[2.1] or [2.2], taking into account an associated plating of awidth equal to 30 times the plating thickness.

3 Pillar in aluminium material

3.1 General

3.1.1 The global critical column buckling stress σCB and thelocal critical buckling stress σCL , in N/mm2, of a pillar builtin aluminium material are to be as defined in NR561 Alu-minium Ships, Section 8.

3.1.2 Maximum allowable axial loadThe maximum allowable axial load PC , in kN, is to be asdefined in NR561 Aluminium Ships, Section 8, taking intoaccount the following values of SFCB and SFCS:

SFCL = 1,0

4 Pillar in composite material

4.1 Global column buckling

4.1.1 The compression axial load FA in the pillar, in kN,calculated as defined in [1.2.3] is to comply with the crite-ria defined in NR546 Composite Ships, Section 9, takinginto account the following values of partial safety coeffi-cients: • CV , CF : As defined in Ch 2, Sec 3, [3.2.1]• CBuck = 1,35

4.2 Local buckling

4.2.1 The actual global compression stress in the pillarlaminate σCA, and the main local compression stresses ineach layer of the pillar laminate are to be calculatedaccording to the NR546 Hull in Composite Materials, Sec-tion 9, taking into account the following values of partialsafety coefficients:• CV , CF , CR : As defined in Ch 2, Sec 3, [3.2.1]• CCA = 1,00

Φ 1

1 10FσEA----------–

-------------------=

M00 5 1 t2+( ), M1 M2+( )

u( )cos----------------------------------------------------------=

u 0 5π, 10FσEA----------=

t 1u( )tan

----------------- M2 M1–M2 M1+--------------------- =

utan2– M2 M1–M2 M1+--------------------- utan2≤ ≤

SFCB 0 34fr----, 1 15,+=


NR 600, Chap 4, App 1

APPENDIX 1 CALCULATION OF THE CRITICAL BUCKLING STRESSES

Symbols

E : Young’s modulus, in N/mm2, to be taken equalto:

• for steels in general: E = 2,06⋅105 N/mm2

• for stainless steels: E = 1,95⋅105 N/mm2

ReH : Minimum guaranteed yield stress, in N/mm2, asdefined in Ch 1, Sec 2.

1 General

1.1 Application

1.1.1 General

The requirements of this Appendix apply for the calculationof the critical buckling stresses of platings and stiffeners.

Other values of critical buckling stresses may be taken intoaccount if justified to the Society.

1.1.2 Checking criteria

The buckling check of structure is to be carried out asdefined in Sec 2, [2.3], taking into account the criticalbuckling stresses defined in the present Appendix.

1.2 Materials

1.2.1 The critical buckling stresses are to be calculatedaccording to:

• for steel structure: the present Appendix

• for aluminium structure: NR561 Aluminium Ships

• for composite structure: NR546 Composite Ships.

2 Plating


2.1.1 General

a) General

Plate panels are considered as being simply supported.For specific designs, other boundary conditions may beconsidered, at the Society’s discretion, provided that thenecessary information is submitted for review.

b) Plate panels subjected to compression and bendingstresses:

For plate panels subjected to compression and bendingstresses along one side, with or without shear, as shownin Fig 1, side “b” is to be taken as the loaded side. Insuch case, the compression stress varies linearly from σ1

to σ2 = ψ σ1 (ψ ≤ 1) along edge “b”.

c) Plate panels subjected to bi-axial compression:

For plate panels subjected to bi-axial compression alongsides “a” and “b”, and to shear, as shown in Fig 2, side“a” is to be taken as the side in the direction of the pri-mary supporting members.

d) Plate panels subjected to shear stress:

For plate panels subjected to shear, as shown in Fig 3,side “b” may be taken as either the longer or the shorterside of the panel.

Figure 1 : Buckling of panel subjected to compression and bending



Figure 2 : Buckling of panel subjected to bi-axial compression

Figure 3 : Buckling of panel subjected to shear

2.1.2 Critical buckling for panel submitted to compression/bending stress

a) Buckling under simple compression (see Fig 1)

The critical buckling stress in compression/bending con-dition is to be obtained, in N/mm2, from the followingformulae:

where:

σE : Euler buckling stress, to be obtained, inN/mm2, from the following formula:

t : Minimum thickness of the plate panel, in mm

a, b : Lengths, in m, of the sides of the panel, asshown in Fig 1 and Fig 2

K1 : Buckling factor defined in Tab 1

ν : Poisson’s coefficient

ε : Coefficient to be taken equal to:

• ε = 1 for α ≥ 1

• ε = 1,05 for α < 1 and side “b” stiff-ened by flat bar

• ε = 1,10 for α < 1 and side “b” stiff-ened by bulb section

• ε = 1,21 for α < 1 and side “b” stiff-ened by angle or T-section

• ε = 1,30 for α < 1 and side “b” stiff-ened by primary supporting members.

α = a / b

b) Buckling under double compression (see Fig 2)

The critical buckling stresses σc,a (compression on side a)is to be obtained, in N/mm2, from the following formula:

where:

β : Slenderness of the panel, to be taken equal to:

without being taken less than 1,25.

The critical buckling stresses σc,b (compression on side b)is to be obtained, in N/mm2, from the same formula asfor σc,a , replacing, in β, length a by length b.

2.1.3 Critical buckling for panel submitted to shear stress

The critical shear buckling stress is to be obtained, inN/mm2, from the following formulae (see Fig 3):

where:

τE : Euler shear buckling stress, to be obtained, inN/mm2, from the following formula:

K2 : Buckling factor to be taken equal to:

ν : Poisson’s coefficient

t : Minimum thickness of the plate panel, in mm

a, b : Lengths, in m, of the sides of the panel, asshown in Fig 3

α = a / b

σc σE = for σEReH

2--------≤

σc ReH 1ReH

4σE

---------– = for σE

ReH

2-------->

σEπ2E

12 1 ν2–( )-------------------------- t

b---

2

K1ε10 6–=

σc a,2 25,

β----------- 1 25,

β2-----------–

ReH=

β 103= at--- ReH

E--------

τc τE for τEReH

2 3-----------≤=

τcReH

3-------- 1

ReH

4 3τE

----------------– for τE

ReH

2 3----------->=

τEπ2E

12 1 ν2–( )-------------------------- t

b---

2

K210 6–=

K2 5= 34, 4α2------ for α 1>+

K25 34,

α2-----------= 4 for α 1≤+



Table 1 : Buckling factor K1 for plate panels

3 Secondary stiffeners


3.1.1 The critical buckling stresses for secondary support-ing member are to be obtained, in N/mm2, from the follow-ing formulae:

where:

σE = min (σE1 , σE2 , σE3)

σE1 : Euler column buckling stress, in N/mm2, equal to:

where:

Ie : Moment of inertia, in cm4, of thestiffener with attached shell platingof width be, about its neutral axisparallel to the plating

Ae : Sectional area, in cm2, of the stiffenerwith attached plating of width be

σE2 : Euler torsional buckling stress, in N/mm2, equalto:

where:

Iw : Sectorial moment of inertia, in cm6,of the stiffener about its connectionto the attached plating:• for flat bars:

• for T-sections:

• for angles and bulb sections:

Ip : Polar moment of inertia, in cm4, ofthe stiffener about its connection tothe attached plating:• for flat bars:

• for stiffeners with face plate:

It : St. Venant’s moment of inertia, incm4, of the stiffener withoutattached plating:• for flat bars:


Load pattern Aspect ratio Buckling factor K1

0 ≤ ψ ≤ 1

− 1 < ψ < 0

ψ ≤ − 1

Note 1:

K1’ : Value of K1 calculated for ψ = 0 K1’’ : Value of K1 calculated for ψ = − 1

α 1≥α 1<

8 4,ψ 1 1,+-------------------

α 1α---+

2 2 1,ψ 1 1,+-------------------

1 ψ+( )K1′ ψK1

″ 10ψ 1 ψ+( )+–

α1 ψ–2

------------- 23---≥ 23 9 1 ψ–

2-------------

2

,

α1 ψ–2

------------- 23---< 15 87, 1 87,

α1 ψ–2

-------------

2------------------------- 8 6 α1 ψ–

2-------------

2

,+ +

1 ψ–2

-------------

2

ψ σ2

σ1

-----=

σc σE= for σEReH

2--------≤

σc Rp0 2, 1ReH

4σE

---------– for σE

ReH

2-------->=

σE1 π2EIe

Ae2

-----------10 4–=

σE2π2EIw

104Ip2

------------------ KC

m2------- m2+ 0 385, E

It

Ip

---+=

Iwhw

3 tw3

36------------10 6–=

Iwtfbf

3hw2

12----------------10 6–=

Iwbf

3hw2

12 bf hw+( )2------------------------------- [tfbf

2 2bfhw 4hw2+ +=

+ 3twbfhw] 10 6–

Iphw

3 tw

3-----------10 4–=

Iphw

3 tw

3----------- hw

2 bftf+ 10 4–=

Ithwtw

3

3-----------10 4–=

It13--- hwtw

3 bftf3 1 0 63, tf

bf

----– + 10 4–=



m : Number of half waves, to be takenequal to the integer number suchthat (see also Tab 2):

m2 (m − 1)2 ≤ KC < m2 (m + 1)2

C0 : Spring stiffness of the attached plat-ing:

Table 2 : Torsional buckling of axially loaded stiffenersNumber m of half waves

σE3 : Euler web buckling stress, in N/mm2, equal to:

• for flat bars:


4 Primary stiffeners


4.1.1 The critical buckling stresses for primary supportingmembers are to be obtained as defined in [3].

KC

m 1 2 3

KCC0

4

π4EIw

--------------106=

C0Etp

3

2 73, s--------------10 3–=

0 KC≤ 4< 4 KC≤ 36< 36 KC≤ 144<

σE3 16tW

hW

-------

2

104=

σE3 78tW

hW

-------

2

104=


NR 600

Chapter 5

OTHER STRUCTURES

SECTION 1 SUPERSTRUCTURES AND DECKHOUSES

SECTION 2 OTHER STRUCTURES

SECTION 3 HELICOPTER DECKS AND PLATFORMS

SECTION 4 ADDITIONAL REQUIREMENTS IN RELATION TO THE SERVICE NOTATION OR SERVICE FEATURE ASSIGNED TO THE SHIP

SECTION 5 ANCHORING EQUIPMENT AND SHIPBOARD FITTINGS FOR ANCHORING, MOORING AND TOWING EQUIPMENT


NR 600, Ch 5, Sec 1

SECTION 1 SUPERSTRUCTURES AND DECKHOUSES

Symbols


LLL : Load line length, in m, as defined in Ch 1, Sec 1,[4.1.4]

B : Moulded breadth, in m

s : Length, in m, of the shorter side of the platepanel

: Length, in m, of the longer side of the platepanel

k : Material factor, defined in Ch 1, Sec 2, [2] forsteel and in Ch 1, Sec 2, [3] for aluminiumalloys

μ : Aspect ratio coefficient of the elementary platepanel, equal to:

• if s ≤ 0,45 :

μ = 1

• if s > 0,45 :

σlocam : Local permissible bending stress, in N/mm2, asdefined in Ch 2, Sec 3

τlocam : Local permissible shear stress, in N/mm2, asdefined in Ch 2, Sec 3

m : End stiffener condition coefficient, as defined inCh 4, Sec 4, [1.4]

n : Coefficient navigation defined in Ch 1, Sec 1,Tab 2.

1 General

1.1 Application

1.1.1 The requirements of this Section apply for the scant-ling of plating and associated structures of front, side and aftbulkheads and decks of superstructures and deckhouses,which not contribute to the hull longitudinal strength.

1.1.2 The structure contributing to the hull longitudinalstrength are to be examined taking into account:

• the lateral pressures defined in Ch 3, Sec 3, [2.2.1] andCh 3, Sec 3, [3.1.2]

• the scantling criteria defined in Ch 4, Sec 3, Ch 4, Sec 4and Ch 4, Sec 5.

1.1.3 Materials

Attention is drawn to the selection of building materialswhich is not only to be determined from strength considera-tion, but should also give consideration to structural fireprotection and associated class requirements or FlagAdministration requirements, where applicable.

1.2 Definitions

1.2.1 Superstructure

A superstructure is a decked structure connected to the free-board deck, extending from side to side of the ship or withthe side plating not being inboard of the shell plating than0,04 B.

1.2.2 Deckhouse

A deckhouse is a decked structure other than a superstruc-ture, located on the freeboard deck or above.

1.2.3 Superstructures and deckhouses contributing to the longitudinal strength

A superstructures and/or deckhouses extending over 0,4 Lmay generally be considered as contributing to the hull lon-gitudinal girder strength.

In this case, a global strength analysis as defined in Ch 4,Sec 2 is to be carried out for the structure elements contrib-uting to the hull longitudinal girder strength.

1.2.4 Tiers of superstructures and deckhouses

The lowest tier is normally that which is directly situatedabove the freeboard deck.

The second tier is that located immediately above the low-est tier, and so on.

1.2.5 Standard height of superstructure

The standard height of superstructure is defined in Tab 1.

Table 1 : Standard height of superstructure

μ 1 1, 0 5, s2

2----

–=

Load line length LLL ,

in m

Standard height hS, in m

Raised quarter deck

All othersuperstructures

LLL ≤ 30 0,90 1,80

30 < LLL < 65 0,9 + 0,00667 (LLL − 30) 1,80


NR 600, Ch 5, Sec 1

1.2.6 Position 1 and position 2

a) Position 1 includes:

• exposed freeboard and raised quarter decks

• exposed superstructure decks situated forward of0,25 LLL from the perpendicular, at the forward sideof the stem, to the waterline at 85% of the leastmoulded depth measured from the top of the keel.

b) Position 2 includes:

• exposed superstructure decks situated aft of 0,25 Lfrom the perpendicular, at the forward side of thestem, to the waterline at 85% of the least mouldeddepth measured from the top of the keel and locatedat least one standard height of superstructure abovethe freeboard deck

• exposed superstructure decks situated forward of0,25 LLL from the perpendicular, at the forward sideof the stem, to the waterline at 85% of the leastmoulded depth measured from the top of the keeland located at least two standard heights of super-structure above the freeboard deck.

1.3 Superstructures and deckhouses structure arrangement

1.3.1 General

The general superstructures and deckhouses structurearrangements are to be as defined in Ch 2, Sec 1, [7].

1.3.2 Construction details

Lower tier stiffeners are to be welded to the decks at theirends.

Brackets are to be fitted at the upper and preferably also thelower ends of vertical stiffeners of exposed front bulkheadsof engine casings and superstructures or deckhouses pro-tecting pump room openings.

2 Design loads

2.1 Load point

2.1.1 Lateral pressure is to be calculated at:

• the mid-height of the elementary plate panel, for plating

• mid-span, for stiffeners.

2.2 Lateral pressure on superstructure and deckhouse walls

2.2.1 The lateral pressure of the exposed walls of super-structure and deckhouses, in kN/m², is to be determined asfollows:

where:

a : Coefficient defined in Tab 2

b : Coefficient defined in Tab 3

c : Coefficient equal to:

• for monohull:

• for multihull:

c = 0,50

b1 : Breadth of the superstructure or deckhouse, inm, at the position considered, to be taken notless than 0,25 B1

B1 : Actual maximum breadth of ship on theexposed weather deck, in m, at the positionconsidered

z : Distance, in m, between the base line and thecalculation point

f : Coefficient equal to:

f = 0,1 LWL − 1

pmin : Minimum lateral pressure, in kN/m², defined inTab 4.

When the front wall is sloped aft, the front wall pressuresvalues p and pmin may be reduced by the value of the cosineof the angle α, where α is defined in Fig 1. The value of theangle α is not to be taken greater than 60°.

Table 2 : Coefficient a

Table 3 : Coefficient b

Figure 1 : Angle of superstructure

p 10acn bf z T–( )–[ ] pmin>=

Location a

Front wall

First tier

Second tierand above

Aft wall

Side walls

x/LWL b

x/LWL ≤ 0,25 1,20

0,25 < x/LWL < 0,70 1,00

0,70 ≤ x/LWL < 0,85 1,30

0,85 ≤ x/LWL 1,70

c 0 30 0 70b1

B1

-----,+,=

2LWL

120----------+

1LWL

120----------+

0 5,LWL

1000-------------+

0 5,LWL

150----------+


NR 600, Ch 5, Sec 1

Table 4 : Minimum lateral pressurefor superstructures and deckhouses

2.3 Pressures on superstructure decks

2.3.1 Exposed deck

The pressure on exposed decks, in kN/m², are defined in Ch 3,Sec 3, [2.2.2].

2.3.2 Accommodation decks

The pressure on accommodation decks, in kN/m², aredefined in Ch 3, Sec 4, [4.2].

3 Plating

3.1 General

3.1.1 Application

The present Article is applicable for the scantling of platingof front, side and aft bulkheads and decks of superstructuresand deckhouses

3.2 Plating scantling

3.2.1 Scantling for steel and aluminium plating

As a rule, the thickness of plating, in mm, is to be not lessthan the following value:

where:

p : Lateral pressure, in kN/m2 as defined in [2.2.1]

λ : Corrosion coefficient taken, in the present Sec-tion, equal to:

• 1,1 for steel plate

• 1,0 for aluminium plate

tmin : Minimum thickness as defined in [3.2.2].

For decks sheathed with wood, the thickness t may bereduced by 10%.

3.2.2 Minimum thicknessAs a rule, the minimum thickness tmin , in mm, is to be notless than:

• for steel structure: 3,2 + 0,03 LWL k1/2

• for aluminium structures: 1,3 LWL1/3 k1/2

without being less than 3,5 mm for rolled products and2,5 mm for extruded products.

3.2.3 Scantling for composite panelThe scantling of composite and plywood panels are to bechecked according to:

• the local loads defined in [2]

• the safety coefficients defined in Ch 2, Sec 3, [3] forcomposite and Ch 2, Sec 3, [4] for plywood, and

• the calculation methodology defined in NR546 Com-posite Ships.

4 Ordinary stiffeners

4.1 General

4.1.1 ApplicationThe present Article is applicable for the scantling of ordi-nary stiffeners of front, side and aft bulkheads and decks ofsuperstructures and deckhouses.

4.1.2 End stiffener condition for calculationThe connection of secondary stiffeners with surroundingsupporting structure is taken into account in the rule sectionmodulus, using coefficient m as defined in Ch 4, Sec 4,[1.4].

4.2 Ordinary stiffener scantling

4.2.1 Scantling for steel and aluminium ordinary stiffeners

As a rule, the section modulus Z, in cm3, and the shear areaAsh, in cm2, of the secondary stiffeners sustaining laterallocal loads are to be not less than the values obtained fromthe following formulae:

where:

Ct : Reduction coefficient, equal to:

p : Lateral pressure, in kN/m2, as defined in [2.2.1]

λ : Corrosion coefficient taken, in the present Sec-tion, equal to:

• 1,1 for steel plate

• 1,0 for aluminium plate

Zmin : Minimum section modulus as defined in[4.2.2].

Type of wall Location pmin

Unprotected front wall

lower tier, x/LWL ≥ 0,70 21 n

lower tier, x/LWL < 0,70 15 n

upper tiers 10 n

Protected front wall or side walls

lower tier 10 n

second tier 7 n > 5

upper tiers 5

Unprotected aft wall

lower tier, x/L ≤ 0,25 10 n

lower tier, x/L > 0,25 7 n > 5

upper tier 5

Protected aft wall anywhere 5

Note 1: n : Navigation coefficient defined in Ch 1, Sec 1,

[3.1.1] or Ch 1, Sec 1, [3.2.1].

t 22 4, λμs pσlocam

-------------- tmin≥=

Z 1000λ ps2

m σlocam⋅----------------------- Zmin>=

Ash 5λCtps

τlocam

-------------=

Ct 1 s2------–=


NR 600, Ch 5, Sec 1

4.2.2 Minimum section modulus

As a rule, the minimum section modulus Zmin , in cm3, ofsecondary stiffeners calculated according to the presentSection are not to be less than:

• for steel stiffener: 3,5 + 0,03 LWL k

• for aluminium stiffeners: 1,7 LWL1/3 k

4.2.3 Scantling for composite ordinary stiffeners

The scantling of composite and plywood ordinary stiffenersare to be checked according to:

• the local loads defined in [2]

• the safety coefficients defined in Ch 2, Sec 3, [3] forcomposite and Ch 2, Sec 3, [4] for plywood, and

• the calculation methodology defined in NR546 Com-posite Ships.

5 Primary stiffeners

5.1 General

5.1.1 The requirements for the scantling of primary stiffen-ers are to be as defined in [4] for ordinary stiffeners for iso-lated beam calculation.

As a rule, the boundary condition to take into account foran isolated beam calculation is to correspond to m = 10.

When deemed necessary to the Society, it may be requestedto carry out a two or three dimensional beam analysis cal-culations as defined in Ch 4, Sec 5, [1.2].

6 Arrangement of superstructures and deckhouses openings

6.1 General

6.1.1 The scope of application of the present Article isdefined in Tab 5.

6.2 External openings

6.2.1 All external openings leading to compartmentsassumed intact in the damage analysis (which are below thefinal damage waterline) are required to be watertight and ofsufficient strength.

6.2.2 No openings, be they permanent openings, recessedpromenades or temporary openings such as shell doors,windows or ports, are allowed on the side shell between theembarkation station of the marine evacuation system andthe waterline in the lightest seagoing condition.

Windows and sidescuttles of the non-opening type areallowed if they have a fire integrity at least equal to A-0 class.

6.2.3 Other closing appliances which are kept permanentlyclosed at sea to ensure the watertight integrity of externalopenings are to be provided with a notice affixed to eachappliance to the effect that it is to be kept closed. Manholesfitted with closely bolted covers need not be so marked.

Table 5 : Scope of application

7 Sidescuttles, windows and skylights

7.1 General

7.1.1 Application

The requirements in [7.2] to [7.4] apply to sidescuttles andrectangular windows providing light and air, located inpositions which are exposed to the action of sea and/or badweather.

7.1.2 Sidescuttle definition

Sidescuttles are round or oval openings with an area notexceeding 0,16 m2.

7.1.3 Window definition

Windows are rectangular openings generally, having aradius at each corner relative to the window size in accord-ance with recognised national or international standards,and round or oval openings with an area exceeding0,16 m2.

7.1.4 Materials and scantlings

As a rule, sidescuttles and windows together with theirglasses, deadlight and storm covers, if fitted, are to be ofapproval design and substantial construction in accordancewith, or equivalent to, recognised national or internationalstandards.

7.2 Opening arrangement

7.2.1 General

Sidescuttles are not to be fitted in such a position that theirsills are below a line drawn parallel to the freeboard deck atside and having its lowest point 0,025 B or 0,5 m, which-ever is the greater distance, above the summer load water-line (or timber summer load waterline if assigned).

Gross tonnage ≤ 500 (1) > 500 (2)

Length LLL ≤ 65 or 90 m (3) ≤ 65 or 90 m (3)

Sidescuttles, windows and skylights

NR566 [7]

Door arrangements NR566 [8]

Freing ports NR566 NR467

Machinery space openings

NR566 NR467

Companionway NR566 NR467

Ventilation openings NR566 NR467

(1) Except ships having the following service notations:• passenger ship with unrestricted navigation• ro-ro passenger ship with unrestricted navigation• fishing vessel, or• chemical tanker

(2) And ships having the service notations defined in (1),whatever their tonnage

(3) 65 m for cargo ships and 90 m for non-cargo ships asdefined in Ch 1, Sec 1, [1.1.2].


NR 600, Ch 5, Sec 1

7.2.2 Sidescuttles below (1,4 + 0,025 B) m above the water

Where in ‘tweendecks the sills of any of the sidescuttles arebelow a line drawn parallel to the bulkhead deck at sideand having its lowest point (1,4 + 0,025 B) m above thewater when the ship departs from any port, all the sidescut-tles in that ‘tweendecks are to be closed watertight andlocked before the ship leaves port, and they may not beopened before the ship arrives at the next port. In the appli-cation of this requirement, the appropriate allowance forfresh water may be made when applicable.

For any ship that has one or more sidescuttles so placed thatthe above requirements apply when it is floating at its deep-est subdivision load line, the Society may indicate the limit-ing mean draught at which these sidescuttles are to havetheir sills above the line drawn parallel to the bulkheaddeck at side, and having its lowest point (1,4 + 0,025 B) mabove the waterline corresponding to the limiting meandraught, and at which it is therefore permissible to departfrom port without previously closing and locking them andto open them at sea under the responsibility of the Masterduring the voyage to the next port. In tropical zones asdefined in the International Convention on Load Lines inforce, this limiting draught may be increased by 0,3 m.

7.2.3 Cargo spaces

No sidescuttles may be fitted in any spaces which areappropriated exclusively for the carriage of cargo.

Sidescuttles may, however, be fitted in spaces appropriatedalternatively for the carriage of cargo or passengers, butthey are to be of such construction as to prevent effectivelyany person opening them or their deadlights without theconsent of the Master.

7.2.4 Non-opening type sidescuttles

Sidescuttles are to be of the non-opening type in the follow-ing cases:

• where they become immersed by any intermediate stageof flooding or the final equilibrium waterplane in anyrequired damage case for ships subject to damage sta-bility regulations

• where they are fitted outside the space consideredflooded and are below the final waterline for those shipswhere the freeboard is reduced on account of subdivi-sion characteristics.

7.2.5 Opening of side scuttle

All sidescuttles, the sills of which are below the bulkheaddeck for passenger ships or the freeboard deck for cargoships, are to be of such construction as to prevent effectivelyany person opening them without the consent of the Masterof the ship.

7.2.6 Manholes and flush scuttles

Manholes and flush scuttles in positions 1 or 2, or withinsuperstructures other than enclosed superstructures, are tobe closed by substantial covers capable of being madewatertight. Unless secured by closely spaced bolts, the cov-ers are to be permanently attached.

7.2.7 Ships with several decks

In ships having several decks above the bulkhead deck,such as passenger ships, the arrangement of sidescuttles andrectangular windows is considered by the Society on acase-by-case basis.

Particular consideration is to be given to the ship side up tothe upper deck and the front bulkhead of the superstructure.

7.2.8 Automatic ventilating scuttles

Automatic ventilating sidescuttles are not to be fitted in theshell plating below the bulkhead deck of passenger shipsand the freeboard deck of cargo ships without the specialagreement of the Society.

7.2.9 Window arrangement

Windows may not be fitted below the freeboard deck, infirst tier end bulkheads or sides of enclosed superstructuresand in first tier deckhouses considered as being buoyant inthe stability calculations or protecting openings leadingbelow.

7.2.10 Skylights

Fixed or opening skylights are to have glass thickness appro-priate to their size and position as required for sidescuttlesand windows. Skylight glasses in any position are to be pro-tected from mechanical damage and, where fitted in posi-tion 1 or 2, to be provided with permanently attachedrobust deadlights or storm covers.

7.2.11 Gangway, cargo and fuelling ports

Gangway, cargo and fuelling ports fitted below the bulk-head deck of passenger ships and the freeboard deck ofcargo ships are to be watertight and in no case they are tobe so fitted as to have their lowest point below the summerload line.

7.3 Glasses

7.3.1 General

In general, toughened glasses with frames of special typeare to be used in compliance with, or equivalent to, recog-nised national or international standards.

The use of clear plate glasses is considered by the Societyon a case-by-case basis.

7.3.2 Scantling

The windows and sidescuttles scantling defined in this sub-article are equivalent to Standard ISO 21005:2004.

The edge condition of window and sidescuttle are consid-ered as simple supported in the scantling formula.

7.3.3 Material

Attention is drawn to the use of plastic materials (PMMA,PC...) from a structural fire protection point of view.

The Flag Administration may request that international con-vention be applied instead of the present requirements,entailing in some cases a use limitation of these materials.


NR 600, Ch 5, Sec 1

7.3.4 Thickness of monolithic windowThe thicknesses, in mm, of monolithic windows and side-scuttles are to be obtained from the following formulae:• rectangular window or sidescuttle:

• circular window or sidescuttle:

where:s : Shorter side, in m, of rectangular window or

sidescuttle

: Longer side, in m, of rectangular window orside scuttle

d : Diameter, in m, of circular window or sidescuttlep : Lateral pressure, in kN/m2 as defined in [2.2.1]Rm : Guaranteed minimum flexural strength, in

N/mm2, of material used given by the manufac-turer.When this value is not available, Rm may betaken at a preliminary design stage equal to:• for glass thermally tempering (toughened):

Rm = 180 N/mm2

• for glass chemically toughened:

Rm = 250 N/mm2

• for polymethacrylate (PMMA):

Rm = 100 N/mm2

• for polycarbonate:

Rm = 80 N/mm2

Sf : Safety factor taken equal to: • for glass window: Sf = 5,0

• for plastic window: Sf = 4,5

β : Aspect ratio coefficient of the rectangular win-dow or sidescuttle, obtained from Tab 6.

Table 6 : Coefficient β

7.3.5 Thickness of laminated windowLaminated windows are glass windows realized by placinga layer of resin (polyvinyl butyral as a general rule) betweentwo sheets of glass.

The thickness of laminated window is to be calculated asdefined in [7.3.4], considering the total thickness of thelaminated window as a monolithic window.

7.3.6 Thickness of double windows

Double windows are glass windows realized by two sheetsof glass, separated by a spacebar hermetically sealed.

The thickness of the outside glass exposed to loads is to becalculated as defined in [7.3.4].

7.3.7 Thickness of glasses forming screen bulkheads or internal boundaries of deckhouses

The thickness of glasses forming screen bulkheads on theside of enclosed promenade spaces and that for rectangularwindows in the internal boundaries of deckhouses whichare protected by such screen bulkheads are considered bythe Society on a case-by-case basis.

The Society may require both limitations on the size of rec-tangular windows and the use of glasses of increased thick-ness in way of front bulkheads which are particularlyexposed to heavy sea.

7.4 Deadlight arrangement glasses

7.4.1 General

Sidescuttles to the following spaces are to be fitted with effi-cient hinged inside deadlights:

• spaces below the freeboard deck

• spaces within the first tier of enclosed superstructures

• first tier deckhouses on the freeboard deck protectingopenings leading below or considered buoyant in stabil-ity calculations.

Deadlights are to be capable of being closed and securedwatertight if fitted below the freeboard deck and weather-tight if fitted above.

7.4.2 Watertight deadlights

Efficient hinged inside deadlights, so arranged that they canbe easily and effectively closed and secured watertight, areto be fitted to all sidescuttles except that, abaft one eighth ofthe ship's length from the forward perpendicular and abovea line drawn parallel to the bulkhead deck at side and hav-ing its lowest point at a height of (3,7 + 0,025 B) m abovethe deepest subdivision summer load line, the deadlightsmay be portable in passenger accommodation other thanthat for steerage passengers, unless the deadlights arerequired by the International Convention on Load Lines inforce to be permanently attached in their proper positions.Such portable deadlights are to be stowed adjacent to thesidescuttles they serve.

7.4.3 Openings at the side shell in the second tier

Sidescuttles and windows at the side shell in the secondtier, protecting direct access below or considered buoyantin the stability calculations, are to be provided with effi-cient, hinged inside deadlights capable of being effectivelyclosed and secured weathertight.

/s β

1,0 0,284

1,5 0,475

2,0 0,608

2,5 0,684

3,0 0,716

3,5 0,734

≥ 4,0 0,750

t 27 4s βpSf

Rm

-----------,=

t 17 4d pSf

Rm

--------,=


NR 600, Ch 5, Sec 1

7.4.4 Openings set inboard in the second tierSidescuttles and windows set inboard from the side shell inthe second tier, protecting direct access below to spaceslisted in [7.4.1], are to be provided with either efficient,hinged inside deadlights or, where they are accessible, per-manently attached external storm covers of approveddesign and substantial construction capable of being effec-tively closed and secured weathertight.

Cabin bulkheads and doors in the second tier separatingsidescuttles and windows from a direct access leading belowmay be accepted in place of fitted deadlights or storm covers.Note 1: Deadlights in accordance with recognised standards arefitted to the inside of windows and sidescuttles, while storm coversof comparable specifications to deadlights are fitted to the outsideof windows, where accessible, and may be hinged or portable.

7.4.5 Deckhouses on superstructures of less than standard height

Deckhouses situated on a raised quarterdeck or on a super-structure of less than standard height may be treated asbeing on the second tier as far as the provision of deadlightsis concerned, provided the height of the raised quarterdeckor superstructure is not less than the standard quarterdeckheight.

7.4.6 Openings protected by a deckhouse

Where an opening in a superstructure deck or in the top ofa deckhouse on the freeboard deck which gives access to aspace below the freeboard deck or to a space within anenclosed superstructure is protected by a deckhouse, then itis considered that only those sidescuttles fitted in spaceswhich give direct access to an open stairway need to be fit-ted with deadlights.

8 Door arrangements

8.1 General

8.1.1 Access openings cut in sides of enclosed superstruc-tures are to be fitted with doors made of equivalent materialto the surrounding structure, and permanently attached.

Special consideration is to be given to the connection ofdoors to the surrounding structure.

Securing devices which ensure watertightness are toinclude tight gaskets, clamping dogs or other similar appli-ances, and are to be permanently attached to the bulkheadsand doors. These doors are to be operable from both sides.


NR 600, Ch 5, Sec 2

SECTION 2 OTHER STRUCTURES

Symbols


T : Draught, at full load displacement, in m, asdefined in Ch 1, Sec 1, [4.4]

k : Material factor defined in Ch 1, Sec 2, [2.1.5]for steel, and in Ch 1, Sec 2, [3.1.2] for alumin-ium.

1 Fore part structure

1.1 General

1.1.1 Application

The requirements of this Article apply for the scantling andthe structure arrangement of structures located forward ofthe collision bulkhead.

Adequate tapering is to be ensured between the structure inthe fore part and the structure aft of the collision bulkhead.

1.1.2 Scantlings

The scantling of the fore part structure and the flat bottomarea are to be checked as defined in Chapter 4.

Fore peak structures which form the boundary of spaces notintended to carry liquids, and which do not belong to theouter shell, are to be subjected to lateral pressure in flood-ing conditions. Their scantlings are to be determined asdefined in Chapter 4.

As a rule, secondary and primary stiffeners on side shell areto be calculated according to Ch 4, Sec 4, taking intoaccount a connection with surrounding structure in simplysupported end conditions (m = 8 in the section modulus for-mulae).

1.2 Stems

1.2.1 General

Adequate continuity of strength is to be ensured at the con-nection of stems and surrounding structure. Abrupt changesin sections are to be avoided.

1.2.2 Bar stems

The cross-sectional area, in cm2, of bar stems is to be notless than:

• for steel structure:

with 0,05 < T/LWL < 0,075

• for aluminium structure:

with 0,05 < T/LWL < 0,075

The thickness of the bar stem, in mm, is to be not less than:

• for stem in steel:

t = (0,40 LWL + 13) k0,5

• for stem in aluminium:

t = (0,55 LWL + 18) k0,5

The cross-sectional area of the stem may be graduallytapered from the load waterline to the upper end, where itmay be equal to the two thirds of the value as calculatedabove.

The lower part of the stem may be constructed of cast steelor aluminium alloy casting subject to the examination bythe Society. Where necessary, a vertical web is to be fittedfor welding of the centre keelson.

The bar stem is to be welded to the bar keel generally withbutt welding.

The shell plating is also to be welded directly to the barstem with butt welding.

1.2.3 Plate stemsWhere the stem is constructed of shaped plates, the thicknessof the plates below the load waterline is to be not less thanthe value obtained, in mm, from the following formulae:

• for steel structure:

• for aluminium structure:

Above the load waterline, this thickness may be gradu-ally tapered towards the stem head, where it is to be notless than that required for side plating at ends.

As a rule, the expanded width of the stem, in m, is not to beless than:

The plating forming the stems is to be supported by horizon-tal diaphragms spaced about 1000 mm apart and con-nected, as far as practicable, to the adjacent frames and sidestringers.

If considered necessary, and particularly where the stemradius is large, a centreline stiffener or web of suitablescantlings is to be fitted.

Ap 0 40, 10 TLWL

--------+ 0 009L2, 20+( )k0 5,=

Ap 0 40, 10 TLWL

--------+ 0 0125L2, 28+( )k0 5,=

tS 1 37 0 95, LWL+( )k0 5,,=

tS 1 90 0 95, LWL+( )k0 5,,=

b 0 8, 0 5LWL

100----------,+=


NR 600, Ch 5, Sec 2

1.3 Reinforcements of the flat bottom forward area

1.3.1 General

In addition to the requirements in [1.1], the structures of theflat bottom forward area are to be able to sustain thedynamic pressures due to the bottom impact where applica-ble as defined in Ch 3, Sec 3, [3.2.1].

1.3.2 Scantlings

The area defined in Ch 3, Sec 3, [3.2.2] is to be reinforcedas defined below:

a) Plating and secondary stiffeners

The scantlings of plating and secondary stiffeners are tobe not less than the values obtained in Ch 4, Sec 3,[2.2.2] and Ch 4, Sec 4, [2.2.2], taking into account thebottom impact pressure pBi defined in Ch 3, Sec 3,[3.2.3].

b) Primary stiffener structure

As a rule, primary structure is to be checked throughdirect calculation considering a pressure of 0,3 pBi ,where pBi is the bottom impact pressure defined in Ch 3,Sec 3, [3.2.3].

c) Tapering

Outside the flat bottom forward area, scantlings are tobe gradually tapered so as to reach the values requiredfor the areas considered.

1.4 Bow flare

1.4.1 General

a) Bow flare structure

The bow flare area is the area extending forward of0,9 LWL from the aft end of LWL and above the summerload waterline up to the level at which a knuckle withan angle greater than 15° is located on the side shell.

The bow flare structure is to be checked as defined inChapter 4 taking into account the external pressuredefined in Ch 3, Sec 3.

In addition, primary supporting members are generallyto be checked through direct calculations.

When deemed necessary by the Society, the bowimpact pressures to take into account for the structurecheck according to Chapter 4 may be taken equal to thevalues defined in:

• NR467 Steel Ships, Pt D, Ch 11, Sec 3, [3.1.1] forships having the service notation passenger ship

• NR467 Steel Ships, Pt B, Ch 8, Sec 1, [4] for shipshaving other service notations.

b) Bow flare arrangement

Outside the bow flare area, scantlings are to be gradu-ally tapered so as to reach the values required for theareas considered.

Intercostal stiffeners are to be fitted at mid-span wherethe angle between the stiffener web and the attachedplating is less than 70°.

1.5 Bulbous bow

1.5.1 GeneralThe thickness of the shell plating of the fore end of the bulband the first strake above the keel is generally to be not lessthan that required for the stems.

The structure arrangement of the bulbous bow is to be asdefined in NR467 Steel Ships, Ch 8, Sec 1, [2.11].

1.6 Thruster tunnel

1.6.1 Scantling of the thruster tunnel and connection with the hull

The thickness of the tunnel is to be not less than that of theadjacent hull plating.

When the tunnel is not welded to the hull, the connectiondevices are examined by the Society on a case-by-case basis.

2 Aft part structure

2.1 General

2.1.1 ApplicationThe requirements of this Article apply for the scantlings ofstructures located aft of the after peak bulkhead and for thereinforcements of the flat bottom aft area.

Adequate tapering is to be ensured between the scantlingsin the aft part and those fore of the after peak bulkhead. Thetapering is to be such that the scantling requirements forboth areas are fulfilled.

2.1.2 ScantlingThe scantling of the aft part structure is to be checked asdefined in Chapter 4.

Aft peak structures which form the boundary of spaces notintended to carry liquids, and which do not belong to theouter shell, are to be subjected to lateral pressure in flood-ing conditions. Their scantlings are to be determined asdefined in Chapter 4.

As a rule, the minimum thicknesses, in mm, of the followingstructure elements of ship built in steel materials or in alu-minium alloys are to be not less than:• for bottom and side plating:

• for inner bottom plating:

• for strength deck plating:

• for platform and swash bulkhead:

• for web of secondary stiffeners, the lesser of:

-

- the thickness of the attached plating

where:s : Spacing, in m, of secondary stiffeners or pri-

mary supporting members, as applicable.

t 0 03LWL, 5 5,+( )k1 2⁄=

t 3 0 017LWLk1 2⁄, 4 5s,+ +=

t 2 3, 0 013LWLk1 2⁄, 4 5s,+ +=

t 2 3, 0 004LWLk1 2⁄, 4 5s,+ +=

t 1 5LWL1 3⁄ K1 6⁄, 1+=


NR 600, Ch 5, Sec 2

2.2 After peak

2.2.1 Arrangement

The structure arrangement of transversely framed after peakstructure is to be as defined in NR467 Steel Ships, Pt B, Ch 8,Sec 2, [3].

2.3 Other structures

2.3.1 Connection of hull structures with the rudder horn

The connection of hull structure with the rudder horn is tobe as defined in NR467 Steel Ships, Pt B, Ch 8, Sec 2, [5].

2.3.2 Sternframes

Sternframes scantling, arrangement and connection to thehull are to be as defined in NR467 Steel Ships, Pt B, Ch 8,Sec 2, [6].

3 Machinery spaces

3.1 Application

3.1.1 The requirements of this Article apply for the arrange-ment and scantling of machinery space structures as regardsgeneral strength. It is no substitute to machinery manufac-turer’s requirements which have to be dealt with at Shipyarddiligence.

The Designer may propose arrangements and scantlingsalternative to the requirements of this Article, on the basis ofdirect calculations which are to be submitted to the Societyfor examination on a case-by-case basis.

The Society may also require such direct calculations to becarried out whenever deemed necessary.

3.2 General

3.2.1 Unless otherwise specified in this Article, the scant-ling of platings and stiffeners in the machinery space are tobe determined according to the relevant criteria in Chapter4, as applicable. In addition, specific requirements speci-fied in this Section apply.

3.2.2 The structural continuity of the machinery space withhull structures located aft and forward is to be as defined inCh 2, Sec 1.

3.2.3 Machinery space openings and access doors to cas-ings are to be in accordance with:

• NR467 Steel Ships for ships of 500 GT and over and forall ships having the service notation passenger ship, ro-ro passenger ship, fishing vessel or chemical tanker

• NR566 for the other ships.

3.3 Double bottom

3.3.1 General

The general double bottom arrangement is to be as definedin Ch 2, Sec 1, [3].

Access arrangement is to be as defined in Ch 2, Sec 2, [5.2].However, the number and size of manholes in floorslocated in way of seatings and adjacent areas are to be keptto the minimum necessary for double bottom access andmaintenance.

3.3.2 Primary structure scantling

The scantling of double bottom primary structure, for steeland aluminium alloys, is to be as defined in Ch 4, Sec 5. Inaddition, the thickness t, in mm, of floor and girder webs isto be not less than:

t = 5 + 0,045 L k1/2

3.3.3 Double bottom girders

In the machinery space the number of side bottom girders isto be adequately increased, with respect to the adjacentareas, to ensure adequate rigidity of the structure.

The side bottom girders are to be a continuation of any bot-tom longitudinal in the areas adjacent to the machineryspace and are generally to have a spacing not greater than3 times that of longitudinal and in no case greater than 3 m.

Additional side bottom girders are to be fitted in way ofmachinery seatings.

Side bottom girders arranged in way of main machineryseatings are to extend for the full length of the machineryspace.

Where the machinery space is situated amidships, the bot-tom girders are to extend aft of the after bulkhead of suchspace for at least three frame spaces, and beyond to be con-nected to the hull structure by tapering.

Where the machinery space is situated aft, the bottom gird-ers are to extend as far aft as practicable in relation to theshape of the bottom and to be supported by floors and sideprimary supporting members at the ends.

3.3.4 Double bottom floors

As a rule, floors are to be fitted in way of machinery.

3.4 Single bottom

3.4.1 General

The general single bottom arrangement is to be as definedin Ch 2, Sec 1, [3].

Furthermore, additional floors are to be fitted in way ofimportant machinery.

Floors and girders are to be fitted with welded face plates inway of:

• engine bed plates

• thrust blocks

• auxiliary seatings.


NR 600, Ch 5, Sec 2

3.4.2 Primary structure scantlingThe scantling of single bottom primary structure, for steeland aluminium alloys, is to be as defined in Ch 4, Sec 5. Inaddition, the thickness t, in mm, of floor and girder webs isto be not less than:

t = 5 + 0,045 L k1/2

3.5 Side

3.5.1 ArrangementThe type of side framing in machinery spaces is generally tobe the same as adopted in the adjacent areas.

When it is not the case, the structural continuity of themachinery side with surrounding structures located aft andforward is to be as defined in Ch 2, Sec 1, and abrupt struc-tural discontinuities between longitudinally and trans-versely framed structure are to be avoided.

3.6 Platforms

3.6.1 The location and extension of platforms in machineryspaces are to be arranged so as to be a continuation of thestructure of side longitudinals, as well as of platforms andside girders located in the adjacent hull areas.

In general, platform transverses are to be arranged in way ofside or longitudinal bulkhead transverses.

3.7 Pillaring

3.7.1 Pillars are generally to be arranged in way of:

• machinery casing corners and corners of large openingson platforms; alternatively, two pillars may be fitted onthe centreline (one at each end of the opening)

• the intersection of platform transverses and girders

• transverse and longitudinal bulkheads of the superstruc-ture.

In general, pillars are to be fitted with brackets at their ends.

3.7.2 Pillar bulkhead scantlings are to be not less thanthose required in [3.8] for machinery casing bulkheads.

3.8 Machinery casing

3.8.1 The scantlings of plating and stiffeners are to be notless than those obtained according to the applicablerequirements in Chapter 4.

Casings are to be reinforced at the ends by deck beams andgirder associated to pillars.

3.9 Seatings of main engines

3.9.1 GeneralThe scantling of seatings of main engines and thrust bear-ings are to be adequate in relation to the weight and powerof engines and the static and dynamic forces transmitted bythe propulsive installation.

Transverse and longitudinal members supporting the seat-ings are to be located in line with floors and bottom girders.

They are to be so arranged as to avoid discontinuity andensure sufficient accessibility for welding of joints and forsurveys and maintenance.

Seatings are to be adequately connected to floors and gird-ers with flanged brackets.

3.9.2 ScantlingThe scantlings of the structural elements in way of the seat-ings of engines are to be determined by the engine manu-facturer. They are to be checked on the basis of justificativecalculations supplied by the engine manufacturer.

4 Bow doors and inner doors

4.1 General

4.1.1 ApplicationThe requirements of this Article apply to the arrangement,strength and securing of bow doors and inner doors leadingto a complete or long forward enclosed superstructure or toa long non-enclosed superstructure, where fitted to attainminimum bow height equivalence.

4.2 Scantling and arrangement

4.2.1 The scantling of the plating and the secondary stiffen-ers of the bow doors are to be checked as defined in Chap-ter 4 for the fore part of the hull.

4.2.2 Primary supporting members, securing and supporting devices

a) Steel structure:

The primary supporting members, securing and support-ing devices are to be checked according to the designloads and permissible stresses defined in NR467 SteelShips, Pt B, Ch 8, Sec 5.

The additional requirements for the check of primarystiffeners defined in Ch 4, Sec 5, [2.1.2] are applicable.

b) Aluminium structure:

For structures built in aluminium alloys, it is to bechecked that the normal stresses σ, the shear stress τand the equivalent stress σVM , induced in the primarysupporting members and in the securing and supportingdevices of bow doors by the design loads defined inNR467 Steel Ships, Pt B, Ch 8, Sec5, are in compliancewith the following conditions:

σ ≤ σALL

τ ≤ τALL

σVM = (σ2 + 3 τ2) 0,5 ≤ σVM,ALL

where:

σALL : Allowable normal stress, in N/mm2, equal to:

σALL = 50 / k

τALL : Allowable shear stress, in N/mm2, equal to:

τALL = 35 / k

σVM,ALL : Allowable equivalent stress, in N/mm2,equal to:

σVM,ALL = 65 / k


NR 600, Ch 5, Sec 2

4.3 Securing and locking arrangement

4.3.1 The securing and locking arrangement are to be asdefined in NR467 Steel Ships, Pt D, Ch 8, Sec 5, [7].

4.4 Operating and Maintenance Manual

4.4.1 An Operating and Maintenance Manual for the bowdoor and inner door is to be provided on board and is tocontain the necessary information defined in NR467 SteelShips, Pt B, Ch 8, Sec 5, [8].

5 Side doors and stern doors

5.1 General

5.1.1 Application

The requirements of this Article apply to the arrangement,strength and securing of side doors, abaft the collision bulk-head, and of stern doors leading to enclosed spaces.

5.2 Scantling and arrangement

5.2.1 The scantling of the plating and the secondary stiffen-ers of the side doors and stern doors are to be checked asdefined in Chapter 4 for side hull.

Where doors also serve as vehicle ramps, the thickness ofthe door plating and the scantling of the secondary stiffen-ers are to be as defined in Chapter 4 under wheeled loads.

The primary supporting members, securing and supportingdevices are to be checked as defined in:

a) For steel structure:

NR467 Steel Ships, Pt B, Ch 8, Sec 6, [2] for the designloads and permissible stresses as defined in NR467 SteelShips, Pt B, Ch 8, Sec 6

b) For aluminium structure:

NR467 Steel Ships, Pt B, Ch 8, Sec 6, [2] for the designloads and permissible stresses as defined in [4.2.2], b).

The additional requirements for the check of primary stiffen-ers defined in Ch 4, Sec 5, [2.1.2] are applicable.

5.3 Securing and locking arrangement

5.3.1 Securing and locking arrangement are to be asdefined in NR467 Steel Ships, Pt B, Ch 8, Sec 6, [6].

5.4 Operating and Maintenance Manual

5.4.1 An Operating and Maintenance Manual for the sidedoors and stern doors is to be provided on board and is tocontain the necessary information defined in NR467 SteelShips, Pt B, Ch 8, Sec 6, [7].

6 Hatch covers

6.1 Small hatch covers

6.1.1 Definition

Small hatches are hatches designed for access to spacesbelow the deck and are capable to be closed weathertightor watertight, as applicable. Their opening is generally lessthan or equal to 2,5 m2.

6.1.2 Scantling

a) Hatches fitted on exposed deck or on non-exposed deck

The scantling of plating and stiffeners of hatch coamingsand hatch covers are to be not less than that of the adja-cent deck structure, calculated according to Chapter 4,based on the same spacing.

b) Hatches fitted on the exposed fore deck

The scantling and the arrangement of hatch covers andhatch coamings exposed on the fore deck are examinedas defined in NR467 Steel Ships, Pt B, Ch 8, Sec 8 [3].

6.1.3 Arrangements

The arrangement of access, height of coamings, securingand closing devices is to be as defined in NR467 Steel Ship,Pt B, Ch 8, Sec 8.

6.2 Large hatch covers

6.2.1 Definition

Large hatches are hatches with openings greater than2,5 m2.

6.2.2 General

The requirements of the present sub-article apply for thescantling and the arrangement of large hatch covers andhatch coamings of stiffened plate construction and its clos-ing arrangements built in steel.

The arrangement of hatch covers built in other materials areexamined by the Society on a case-by-case basis.

6.2.3 Scantling and arrangement

Excepted where specified in [6.2.5], the scantling and thearrangement of hatch covers and hatch coamings are exam-ined on a case-by-case basis, based on the requirementsdefined in NR467 Steel Ships, Pt B, Ch 8, Sec 7.

6.2.4 Buckling strength of hatch coamings

When the hatch coamings contribute to the longitudinalhull girder strength, the buckling strength assessment ofcoaming parts is to be carried out according to Ch 4, Sec 2.

6.2.5 The scantling and the arrangement of hatch coversand hatch coamings for ship having the service notationbulk carrier, ore carrier and combination carrier are to beas defined in NR467 Steel Ships, Pt D, Ch 4, Sec 4.


NR 600, Ch 5, Sec 2

7 Movable decks and inner ramps - External ramps

7.1 Application

7.1.1 The requirements of this Article apply to movabledecks and inner ramps when the additional class notationALP is not granted and when no cargo gear register isissued.

7.1.2 On special request of the owner the movable innerramps under load may be examined by the Society in thescope of the application of NR526 Rules for the Certifica-tion of Lifting Appliances on board Ships and OffshoreUnits and the assignment of additional class notation ALP(see NR467 Steel Ships, Pt A, Ch 1, Sec 2).

7.2 Scantling

7.2.1 Materials

The movable decks and inner ramps are to be made of steelor aluminium alloys complying with the requirements ofNR216 Materials and Welding. Other materials of equiva-lent strength may be used, subject to a case-by-case exami-nation by the Society.

7.2.2 Plating and secondary stiffener scantling

The thickness of plate panels and the section modulus andshear sectional area of secondary stiffeners subjected towheeled loads are to be not less than the value obtainedfrom Ch 4, Sec 3 and Ch 4, Sec 4, as applicable, with avalue of Fw ⋅ n (or Fw for secondary stiffeners) to be taken notless than 5 kN, where:

Fw : Wheeled force, in kN, as defined in Ch 3, Sec 4,[3.3]

n : Number of wheels on the plate panel as definedin Ch 4, Sec 3, [2.2.4].

7.3 Primary supporting members

7.3.1 General

The supporting structure of movable decks and inner rampsis to be examined through direct calculation, consideringthe following cases:

• movable deck stowed in upper position, empty andlocked, at sea

• movable deck in service, loaded, in lower position, rest-ing on supports or supporting legs and locked, at sea

• movable inner ramp in sloped position, supported byhinges at one end and by a deck at the other, with possi-ble intermediate supports, loaded, at harbour

• movable inner ramp in horizontal position, loaded andlocked, at sea.

7.3.2 Loading cases

The scantlings of the structure are to be checked in both seaand harbour conditions for the following cases:

• loaded movable deck or inner ramp under loadsaccording to the load distribution indicated by theDesigner

• loaded movable deck or inner ramp under uniformlydistributed loads corresponding to a pressure, in kN/m2,equal to p0 + p1

• empty movable deck under uniformly distributed massescorresponding to a pressure, in kN/m2, equal to p0

where:

PP : Mass of the movable deck, in kN

PV : Mass of a vehicle, in kN

nV : Maximum number of vehicles loaded on themovable deck

AP : Effective area of the movable deck, in m2.

7.3.3 Lateral pressure

The vertical and lateral pressures p, in kN/m2 transmitted tothe movable deck or inner ramp structures in x, y and zdirections to take into account in harbour and sea condi-tions are to be obtained from Tab 1.

7.3.4 Checking criteria

It is to be checked that the combined stress σVM is in accord-ance with the criteria defined in Ch 2, Sec 3.

The scantlings of main stiffeners and the distribution of sup-ports are to be such that the deflection of the loaded mova-ble deck or loaded inner ramp does not exceed 5 mm/m.

7.4 Supports, suspensions and locking devices

7.4.1 Scantlings of wire suspensions are to be checked bydirect calculation on the basis of the loads in [7.3.2] and[7.3.3], taking into account a safety factor at least equal to 5.

It is to be checked that the combined stress σVM in rigid sup-ports and locking devices is in accordance with the criteriadefined in Ch 2, Sec 3.

7.5 Tests and trials

7.5.1 Tests and trials defined in [7.5.2] to [7.5.4] are to becarried out in the presence of the Surveyor. Upon specialrequest, these conditions of tests and trials may be modifiedto comply with any relevant national regulations in use.

7.5.2 The wire ropes are to be submitted to a tensile test ontest-piece.

p0PP

AP

------=

p1 nVPV

AP

------=


NR 600, Ch 5, Sec 2

Table 1 : Movable decks and inner rampslateral pressure

7.5.3 The loose gears used for the platform and ramp han-dling (chain, shackles, removable blocks, etc.) are to have amaximum safe working load (SWL) and are to be submittedto an individual test before fitting on board.

The test of these loose gears are to be in accordance withthe applicable requirements of NR526 Rules for the Certifi-cation of Lifting Appliances on board Ships and OffshoreUnits.

7.5.4 A trial to verify the correct operation of lowering andlifting devices of the platform is to be carried out beforegoing into service.

This trial is made without overload unless special require-ment of National Authorities.

7.6 External ramps

7.6.1 The external ramps are to be able to operate with aheel angle of 5° and a trim angle of 2°.

7.6.2 The thicknesses of plating and the scantlings of sec-ondary stiffeners and primary supporting members are to bedetermined under vehicle loads in harbour condition, atrest, as defined in Tab 1.

7.6.3 The external ramps are to be examined for theirwatertightness, if applicable.

7.6.4 The locking of external ramps in stowage position atsea is examined by the Society on a case-by-case basis.

7.6.5 The ship structure under the reactions due to theramp is examined by the Society on a case-by-case basis.

8 Rudders

8.1 General

8.1.1 The scantling of rudders is to be in accordance withthe requirements defined in NR467 Steel Ships, Pt B, Ch 9,Sec 1.

For high speed ship as defined in Ch 1, Sec 1, [1.1.4], theahead service speed to take into account in the ruddercheck is to be taken equal to the minimum value between:

• VAV

• 2/3 (VAV + 2 LWL0,5)

where:

VAV : Maximum ahead service speed, in knots, atmaximum displacement in steel water.

Rudders built in aluminium alloys or in composite materialsare to be examined on a case-by-case basis by the Society.

8.2 Rudder horn and solepiece scantlings

8.2.1 Rudder horn

The general arrangement and the scantling of rudder horn isto be as defined in NR467 Steel Ships, Pt B, Ch 9, Sec 1, [8].

For rudder horn in aluminium alloys, the allowable stressesto be taken into account are the following ones:


τALL = 20 / k

σE,ALL : Allowable equivalent stress, in N/mm2, equal to:

σE,ALL = 50 / k

σB,ALL : Allowable bending stress, in N/mm2, equal to:

σB,ALL = 30 / k

where:

k : Material factor for aluminium, defined in Ch 1,Sec 2, [3.1.2].

For ships with notation launch or seagoing launch, theallowable stresses may be increased by 10%.

8.2.2 Solepieces

For solepieces in aluminium alloys, the allowable stresses tobe taken into account are the following ones:

σB,ALL : Allowable bending stress, in N/mm2, equal to:

σB,ALL = 35 / k


τALL = 20 / k

For ships with notation launch or seagoing launch, theallowable stresses may be increased by 10%.

Ship condition Lateral pressure p, in kN/m2

Sea

Px = (p0 + p1) ax / g Py = 0,7 (p0 + p1) ay / g Px = (p0+p1) + (p0+p1) η az / g + 0,7 y αR / g

Harbour

during lifting

pz = 1,2 p0

at restpx = 0,035 (p0 + p1)py = 0,087 (p0 + p1)pz = 1,100 (p0 + p1)

Note 1:g : Gravity acceleration taken equal to 9,81 m/s2 ax : Longitudinal acceleration, in m/s2, taken equal to:

ay : Transversal acceleration, in m/s2, taken equal to:


αR : Roll acceleration, in rad/s2, as defined in Ch 3,Sec 4, [2.1.7]

η : Acceleration coefficient to be taken equal to:• 0,5 for ship in displacement mode• 0,4 for ship in planing mode

y, z : Transversal and vertical co-ordinates, in m, ofthe centre of gravity of the ramp

T : Minimum draught of the ship, in m.

ax 0 65zT---, 0 55,+=

ay αR z T–( )=


NR 600, Ch 5, Sec 2

9 Water jet propulsion tunnel

9.1 General

9.1.1 The drawings of water jet duct, ship supporting struc-ture, thrust bearing, as well as shell openings and local rein-forcements are to be submitted for examination.

The pressure in water jet ducts, the forces and momentsinduced by the water jet to the hull structure and the calcu-lation procedure from the Designer are to be specified.

9.1.2 Waterjet supporting structure

The supporting structure of waterjets is to be able to with-stand the loads induced by the waterjet in the followingconditions:

• maximum ahead thrust

• maximum thrust at maximum lateral inclination

• maximum reversed thrust (going astern).

Information on the above loads is to be given by the water-jet manufacturer.

For each waterjet, the following loading cases are to beinvestigated:

LDC1 : Internal hydrodynamic pressure ph in the built-in nozzle

LDC2 : Horizontal longitudinal force Fx1 in normal serv-ice (ahead)

LDC3 : Horizontal transverse force Fy and associatedmoment Mz during steering operation

LDC4 : Horizontal longitudinal force Fx2, vertical forceFz and overturning moment My in crash-stop sit-uation.

The actual location of the thrust bearing is to be adequatelyconsidered (either located aft of the stem in the stator bowlor inside the waterjet compartment).

The scantlings are to be checked by direct calculations.

Tab 2 indicates the loading cases to be considered for thevarious components of the waterjet system. Other loadingcases could be considered for specific or new design.

The stress criteria for static analysis, in N/mm2, may betaken as follows:

• bending stress: σlocam = 0,65 R

• shear stress: τlocam = 0,45 R

• combined stress: σVMam = 0,80 R

(calculated according to Von Mises criteria)

where:

R : Minimum yield stress value defined in Ch 2, Sec3, [2.1.1].

Table 2 : Loading cases

The stress criteria for fatigue analysis are to be specified bythe Designer.

The shell thickness in way of nozzles as well as the shellthickness of the tunnel are to be individually considered. Ingeneral, such thicknesses are to be not less than 1,5 timesthe thickness of the adjacent bottom plating.

General principles to be followed for such structures sub-ject to cyclic loadings are listed hereafter:

• continuous welding

• shear connections between stiffeners and transverseframes

• soft toe brackets

• no sniped ends

• no termination on plate fields

• no scallops in critical areas

• no start and stop of welding in corners or at ends of stiff-eners and brackets

• possibly grinding of toes of critical welds.

As a guidance, the following criteria may be considered:

The bending natural frequency of plates and strength mem-bers of the hull in the area of waterjets should not be lessthan 2,3 times the blade frequency for structures below thedesign waterline and between transom and aft engine roombulkhead. Structural components (such as the casing ofwaterjet and accessory parts and the immersed shell area)which may transfer pressure fluctuations into the ship struc-ture have to fulfil the requirements of the waterjet manufac-turer. Especially with regard the grids installed in the inletduct, the hydrodynamic design should assure an unprob-lematic operation with respect to cavitation phenomenon.

This checking is left to the manufacturers.

Component LDC 1 LDC 2 LDC 3 LDC 4

Built-in nozzle:

- plating X (1) X (2)

- bending behaviour X (3)

Ship stem X (2) X X (4)

Bolting on stem X (5) X (5)

(1) To be checked under lateral pressure and againstfatigue behaviour

(2) Buckling to be checked (100% of Fx transferred bybuilt-in nozzle in case of thrust bearing aft of the stem)

(3) Ratio of My directly sustained by the built-in nozzle tobe estimated on basis of relative stiffnesses

(4) Ratio of My directly sustained by the transom structureto be estimated on basis of relative stiffnesses

(5) Bolting calculation taking account of the actual pre-ten-sion in bolts.


NR 600, Ch 5, Sec 2

10 Foils and trim tab supports

10.1 General

10.1.1 Foils and trim tab supports are not covered withinthe scope of classification and/or certification.

Forces and moments induced by these elements, as well asthe Designer calculation, are to be submitted for the exami-nation of the surrounding hull structure reinforcements.

As a general rule, attachment structure of foils to the hullstructure are to be located within watertight compartmentor equivalent.

11 Propeller shaft brackets

11.1 General

11.1.1 The scantling of propeller shaft brackets, consistingof one or two arms, are to be in accordance with NR467Steel Ships, Pt B, Ch 9, Sec 3.

12 Bulwarks

12.1 General

12.1.1 Arrangement of bulwarks and guard rails

The general arrangement of bulwarks and guard rails is tobe as defined in NR467 Steel Ships, Pt B, Ch 9, Sec 2.

12.1.2 Scantling of bulwarks

The scantling of bulwarks is to be in accordance with thefollowing requirements:

a) Plating and secondary stiffeners

The plating thickness and the secondary stiffeners are tobe as defined in Ch 4, Sec 3, [2] and Ch 4, Sec 4, [2].

b) Stays

The section modulus, in cm3, and the shear section, incm2, of stays and their connection to the deck structurein way of the lower part of the bulwark are to be not lessthan the values obtained from the following formulae:

• for section modulus, the greater value obtainedfrom:

and:

- if s ≥ 0,6:

- if s < 0,6:

• for shear section, the greater value obtained from:

and:

- if s ≥ 0,6:

- if s < 0,6:

where:

ps : Sea pressure on side shell as defined in Ch 3,Sec 3, [2.2.1], in kN/m2

pssmin : Impact pressure on side shell as defined inCh 3, Sec 3, [3.1], in kN/m2

s : Spacing of stays, in m

: Length of stays, in m

σlocam , τlocam : Permissible stresses as defined in Ch 2,Sec 3.

13 Lifting appliances

13.1 General

13.1.1 As a rule, the permanent fixed parts of lifting appli-ances fitted into the hull and their local reinforcements areconsidered as integral part of the hull and are to bechecked.

The forces and moments transmitted by the crane to theship structure are to be submitted to the Society.

For crane not used in offshore conditions having a safeworking load F less than 50 kN, and when the deadweightsof the crane are unknown, the bending moment M, inkN⋅m, induced by the crane pedestal to the hull is to betaken equal to:

M = 2,2 F x0

where:

x0 : Maximum jib radius of the crane, in m.

For cranes having a safe working load greater than 50 kN orfor crane used in offshore conditions, the bending momentand forces induced by the crane pedestal to the hull are tobe as defined in NR526 Rules for the Certification of LiftingAppliances Onboard Ships and Offshore Units.

Local reinforcements and hull structure surrounding thecrane pedestal are to be checked by direct calculations, tak-ing into account the following permissible stresses:

a) For steel and aluminium structure:

σVMam = 0,6 R

where:

σVMam : Combined stress calculated according toVon Mises criteria

R : Minimum yield stress value defined in Ch 2,Sec 3, [2.1.1].

z500pss

2

σlocam

-----------------------=

z280pssmin 0 3,–( )

σlocam

-----------------------------------------------=

z600Epssmin 0 3,–( )

σlocam

--------------------------------------------------=

Ash10pssτlocam

-----------------=

Ash2 8pssmin,

τlocam

-----------------------=

Ash6Epssmin

τlocam

--------------------=


NR 600, Ch 5, Sec 2

b) For composite structure:

SFCRANE = 1,2 SF

SFCSCRANE = 1,2 SFCS

where:

SF : Rules safety factor applicable to maximumstress defined in Ch 2, Sec 3, [3.2.1]

SFCS : Rules safety factor applicable to combinedstress defined in Ch 2, Sec 3, [3.2.2].

For steel and aluminium structure, when inserted plates areprovided in deck, side shell or bulkheads in way of cranefoundation, these inserts are to have well radiused cornersand are to be edge-prepared prior to welding.

14 Protection of metallic hull

14.1 General

14.1.1 The protection of hull metallic structure is to be asdefined in NR467 Steel Ships, Pt B, Ch 10, Sec 1 andincludes the following types of protection:• coating• galvanic corrosion in tanks• wooden ceiling of double bottom (see Note 1)• wood sheathing of decks• batten in cargo side.

Note 1: Wooden ceiling on the inner bottom is not required wherethe thickness of the inner bottom, calculated according to Ch 4,Sec 3, [2], is increased by 2 mm.


NR 600, Ch 5, Sec 3

SECTION 3 HELICOPTER DECKS AND PLATFORMS

Symbols

WH : Maximum weight of the helicopter, in t

AT : Tyre or skid print area, in m2. Where the printarea AT is not specified by the Designer, the fol-lowing values are to be taken into account:

• for one tyre: 0,3 m x 0,30 m

• for one skid: 1,0 m x 0,01 m

γW2 : Coefficient to be taken equal to:

• 1,20 for plating and ordinary stiffeners

• 1,10 for primary stiffeners

g : Gravity acceleration taken equal to 9,81 m/s2.

1 Application

1.1 General

1.1.1 The requirements of this Section apply to areasequipped for the landing and take-off of helicopters withwheels or with landing skids, and located on a deck or on aplatform permanently connected to the hull structure.

1.1.2 Helicopter deck or platform intended for the landingof helicopters having landing devices other than wheels orskids are to be examined by the Society on a case-by-casebasis.

1.2 Definition

1.2.1 Landing gear

A landing gear may consist of a single wheel or a group ofwheels.

2 General arrangement

2.1 Landing area and approach sector

2.1.1 The main dimensions of the landing area, its locationon board, the approach sector for landing and take-off areto comply with the applicable requirements from Nationalor other Authorities.

2.1.2 The landing area and the approach sector are to befree of obstructions above the level of the helicopter deck orplatform.

Note 1: The following items may exceed the height of the landingarea, but not more than 100 mm:

• guttering or slightly raised kerb

• lightning equipment

• outboard edge of the safety net

• foam monitors

• those handrails and other items associated with the landingarea which are incapable of complete retraction or lowering forhelicopter operations.

2.2 Sheathing of the landing area

2.2.1 Within the landing area, a non-skid deck covering isrecommended.

Where the helicopter deck or platform is wood sheathed,special attention is to be paid to the fire protection.

2.3 Safety net

2.3.1 It is recommended to provide a safety net at the sidesof the helicopter deck or platform.

2.4 Drainage system

2.4.1 Gutterways of adequate height and a drainage systemare recommended on the periphery of the helicopter deckor platform.

2.5 Deck reinforcements

2.5.1 Local deck strengthening is to be fitted at the connec-tion of diagonals and pillars supporting platform.

3 Design loads

3.1 Emergency landing load

3.1.1 The emergency landing force FEL transmitted throughone landing gear or one skid to the helicopter deck or plat-form is to be obtained, in kN, from the following formulae:

• helicopter with landing gears:

FEL = 1,25 g WH

• helicopter with landing skids:

FEL = 2,5 g WH

The points of application of this force are to be taken so asto produce the most severe load on the supporting struc-ture.


NR 600, Ch 5, Sec 3

3.2 Garage load

3.2.1 Where a garage zone is fitted in addition to the land-ing area, the local forces FW transmitted by one wheel or agroup of wheels or one skid to the helicopter deck or plat-form are to be obtained, in kN, as specified in Ch 3, Sec 4,[3.3], where M is to be taken equal to:

• for helicopter with landing gears:

M is the landing gear load, in t, to be specified by theDesigner. If the landing gear load is not known, M is tobe taken equal to:

where n is the total number of landing gears

• for helicopter with landing skids:

M = 0,5 WH

3.3 Specific loads for helicopter platforms

3.3.1 The forces applied to an helicopter platform are to bedetermined, in kN, as follows:

• in vertical direction:

• in transverse direction:

• in longitudinal direction:

where:

WH : Maximum weight of the helicopter, in t

Wp : Structural weight of the helicopter platform, in t,to be evenly distributed, and to be taken notless than the value obtained from the followingformula:

Wp = 0,2 AH

AH : Area, in m2, of the entire landing area

AHX, AHY : Vertical areas, in m2, of the helicopter platformin x and y directions respectively. Unless other-wise specified, AHX and AHY may be taken equalto AH / 3

ax : Longitudinal acceleration, in m/s2, equal to:

ay : Transversal acceleration, in m/s2, equal to:


αR : Roll acceleration, in m/s2, as defined in Ch 3,Sec 4, [2.1.7]

y, z : Transversal and vertical co-ordinates, in m, ofthe centre of gravity of the helicopter

T : Minimum draught of the ship, in m.

3.4 Local external pressures

3.4.1 Local external pressures on exposed helicopter deckand platform, and when applicable on exposed garagezone, are to be taken into account in addition to the designloads defined in [3.1], [3.2] and [3.3] and are to be calcu-lated as defined in Ch 3, Sec 3, [2.2.2].

4 Scantlings

4.1 Plating

4.1.1 Load model

The following forces P0 are to be considered independently:

• P0 = FEL

where FEL is the force corresponding to the emergencylanding load, as defined in [3.1.1]

• P0 = 1,1 FW

where FW is the forces corresponding to the garage load,as defined in [3.2.1], if applicable.

4.1.2 Thickness of plating

The thickness of an helicopter deck or platform subjected toforces defined in [4.1.1] is not to be less than the valueobtained according to formula defined for plating subjectedto wheeled loads (see Ch 4, Sec 3, [2.2.4]).

4.1.3 Helicopter with wheels

For helicopters with wheels, in the particular case whereu > s, the tyre print outside of the plate panel is to be disre-garded. In such a case, the load is to be considered as beingfully distributed on the spacing s only (see Fig 1).

Figure 1 : Tyre print with u > s

4.1.4 Helicopter with skids

For helicopters with skids, in the particular case wherev > , the skid print outside of the plate panel is to be disre-garded. In such a case, the load is to be considered as beingfully distributed on the span only (see Fig 2).

M 1 25,n

-------------WH=

FZ WH WP+( ) g az 0 7αRy,+ +( ) 1 2AHY,+=

FY 0 7 WH Wp+( )ay, 1 2AHY,+=

FX WH Wp+( )ax 1 2AHX,+=

ax 0 65zT---, 0 55,+=

ay αR z T–( )=

s

�

v

u


NR 600, Ch 5, Sec 3

Figure 2 : Skid print with v >

4.2 Ordinary stiffeners

4.2.1 Load modelThe following forces P0 are to be considered independently:

• P0 = FEL

where FEl is the force corresponding to the emergencylanding load, as defined in [3.1.1]

• P0 = 1,1 FW

where FW is the forces corresponding to the garage load,as defined in [3.2.1], if applicable

• for an helicopter platform: P0 = 1,1 FW

where FW is the forces corresponding to the garage load,as defined in [3.2.1], if applicable.

4.2.2 Normal and shear stressesThe normal stress σ and the shear stress τ induced by forcesdefined in [4.2.1] in an ordinary stiffener of an helicopterdeck or platform are obtained, in N/mm2, as follows:

where:

m : Coefficient to be taken equal to:

• m = 6 for an helicopter with wheels

• m = 10 for an helicopter with landing skids.

4.2.3 Checking criteriaIt is to be checked that the normal stress σ and the shearstress τ calculated according to [4.2.2], are in compliancewith the following formulae:

where:Ry : Minimum yield stress, in N/mm2, of the mate-

rial, as defined in:• Ch 1, Sec 2, [2.1.5] for steel structure• Ch 1, Sec 2, [3.1.3] for aluminium struc-

ture.

4.3 Primary supporting members

4.3.1 Load modelThe following loads are to be considered independently:• emergency landing load, as defined in [3.1.1]• garage load, as defined in [3.2.1], if applicable• for an helicopter platform, specific loads as defined in

[3.3.1].

The most unfavourable case, i.e. where the maximumnumber of land gears is located on the same primary sup-porting members, is to be considered.

4.3.2 Checking criteriaIt is to be checked that the equivalent stress σVM is in com-pliance with the following formula:

where:Ry : Minimum yield stress, in N/mm2, of the mate-

rial, as defined in [4.2.3].When a two- or three-dimensional beam model calculationor a finite element model calculation is carried out to checkthe primary structure, the permissible stresses in the primarystructure are defined in Ch 2, Sec 3, [2.1.1], b) and in Ch 2,Sec 3, [2.1.1], c), where σVMam is to be taken equal to

0,95 Ry.

s

u

v

�

σ P0

mW-----------103=

τ 10P0

ASh

------------=

0.95Ry σ≥0 45Ry, τ≥

σVM 0.95Ry≤


NR 600, Ch 5, Sec 4

SECTION 4 ADDITIONAL REQUIREMENTS IN RELATION TO

THE SERVICE NOTATION OR SERVICE FEATURE

ASSIGNED TO THE SHIP

Symbols

LWL : Ship‘s length at waterline, in m

L : Reference ship’s length, to be taken equal to LWL

k : Material factor as defined in Ch 1, Sec 2

s : Length, in m, of the shorter side of the platepanel or spacing, in m, of secondary stiffeners,or spacing, in m, of primary supporting mem-bers, as applicable.

1 General

1.1 Service notations and service features

1.1.1 The service notations define the type and/or serviceof the ship which is considered for its classification.

A service notation may be completed by one or more addi-tional service features giving further precision regarding thetype of service of the ship.

The service notation and the additional service features aredefined in NR467 Steel Ships, Pt A, Ch 1, Sec 2, [4].

1.1.2 Additional requirementsThe present Section defines the hull arrangement and hullstructure requirements to be considered in relation to theservice notation or service feature assigned to the ship andto be applied in addition to the other requirements of thepresent Rules (see Tab 1).

1.2 Material

1.2.1 As a rule, the minimum scantlings defined in thepresent section for platings and stiffeners are applicable forships built in steel or aluminium alloys.

2 Ro-ro cargo ships

2.1 Application

2.1.1 Ships having the service notation ro-ro cargo ship are tocomply with the requirements of the present Article and withthe requirements of NR467 Steel Ships, Pt D, Ch 1, Sec 1,where applicable.

2.2 General

2.2.1 Wood sheathingWood sheathing is recommended for caterpillar trucks andunusual vehicles.

Table 1 : List of articles in relation to theservice notation or additional service feature

2.3 Hull scantlings

2.3.1 PlatingThe thickness of the weather strength deck and trunk deckplating is to be not less than the values obtained, in mm,from the following formula:

t = 3,6 + 0,013 L + 4,5 s

where:s : Length, in m, of the shorter side of the plate

panel.

2.3.2 Inner bottom of cargo holds intended to carry dry cargo

The inner bottom thickness calculated as defined in Ch 4,Sec 3, [2] is to be increased by 2 mm unless it is protectedby a continuous wooden ceiling.

Service notation or additional service feature

Reference of Article

Reference Chapter in

NR467, Part D

Ro-ro cargo ship [2] 1

Container ship [3] 2

Livestock carrier [4] 3

Bulk carrier [5] 4

Ore carrier [6] 5

Combination carrier [7] 6

Oil tanker and FLS tanker [8] 7

Chemical tanker [9] 8

Tanker [10] 10

Passenger ship [11] 11

Ro-ro passenger ship [12] 12

Tug [13] 14

Supply vessel [14] 15

Fire-fighting ship [15] 16

Oil recovery ship [16] 17

Cable-laying ship [17] 18

Non-propelled unit [18] 19

Fishing vessel [19] 20

Launch and Seagoing launch [20] −


NR 600, Ch 5, Sec 4

3 Container ships

3.1 Application

3.1.1 Ships having the service notation container ship are tocomply with the requirements of the present Article and withthe requirements of NR467 Steel Ships, Pt D, Ch 2, Sec 1,where applicable.

3.2 General

3.2.1 The additional requirements of this Article apply tocontainer ships intended to carry containers in holds and/oron deck as defined in NR467 Steel Ships, Pt D, Ch 2, Sec 2,[1.1.1].

3.3 Structure design principles

3.3.1 Structure design principles defined in NR467 SteelShips, Pt D, Ch 2, Sec 2, [3] are applicable.

3.4 Design loads

3.4.1 Still water torsional torqueWhen deemed necessary to the Society, the still water tor-sional torque may be considered as defined in NR467 SteelShips, Pt D, Ch 2, Sec 2, [4.1.1].

3.4.2 Forces on containers

a) Still and inertial forces

The vertical forces FZ,i and transversal forces FT,i, in kN,applied to the containers at each level ”i” of a stack areto be calculated as defined in Ch 3, Sec 4, [3.2.3] forthe dry unit cargo, where M, in t, is to be taken equalthe mass of the container.

Where empty containers are stowed at the top of astack, the forces are to be calculated considering weightof empty containers equal to:

• 0,14 times the weight of a loaded container, in thecase of steel containers

• 0,08 times the weight of a loaded container, in thecase of aluminium containers.

b) Wind forces

The forces Fy,wind,i, in y direction applied to one con-tainer stowed above deck at the level “i” due to theeffect of the wind is to be obtained, in kN, from the fol-lowing formula:

Fy,wind,i = 1,2 hC C

where:

C, bC : Dimension, in m, of the container stack inthe ship longitudinal and transverse direc-tion, respectively.

c) Reaction at the corners of stacks of containers

The reaction at the corner of stack are to be calculatedin the two following conditions of navigation:

• ship in upright condition (see Fig 1)

• ship in inclined condition (see Fig 2).

Figure 1 : Corner reactionsin upright condition of navigation

Figure 2 : Corner reactionsin inclined condition of navigation

The forces to be considered as being applied at the cen-tre of gravity of the stack, the reactions at the corners ofstack are to be obtained, in kN, as specified by the fol-lowing formulae:

• in upright condition:

• in inclined condition:

where:

FW,Z : Vertical force in a stack, in kN:

FW,ZZ

X

Y

FW,X

RW,1RW,2

RW,2

Z

X

Y

R W,1RW,2

RW,2

FW,Y

FW,Z

RW 1, RW 2,FW Z,

4----------= =

RW 1,FW Z,

4---------- NhCFW Y,

4bC

----------------------+=

RW 1,FW Z,

4---------- NhCFW Y,

4bC

----------------------–=

FW Z, FZ i,

i 1=

i N=

=


NR 600, Ch 5, Sec 4

FW,Y : Horizontal force in a stack, in kN:

FZ,i, FT,i : Vertical and transversal forces, in kN, asdefined in item a)

N : Number of container per stack.

3.5 Hull scantlings

3.5.1 The hull structure scantling is to be examined takinginto account the loads induced by containers as defined in[3.4].

3.5.2 The thickness of the strake below the sheerstrake isnot to be less than 0,7 times that of the sheerstrake.

3.5.3 The thickness of the strake below the upper strake oftorsion box girders is not to be less than 0,7 times that of theupper strake.

3.5.4 Other structure items

The following items are to be examined as defined in thefollowing requirements of NR467 Steel Ships:

• non-weathertight hatch covers above superstructuredeck: Pt D, Ch 2, Sec 2, [6.1]

• fixed cell guides: Pt D, Ch 2, Sec 2, [7]

• fixed cargo securing devices: Pt D, Ch 2, Sec 2, [8].

3.6 Construction and testing

3.6.1 Special structural details

The specific requirements in NR467 Steel Ships, Pt B, Ch 11,Sec 2, [2.7] for ships with the service notation containership are to be complied with.

4 Livestock carriers

4.1 Application

4.1.1 Ships having the service notation livestock carrier areto comply with the requirements of the present Article andof NR467 Steel Ships, Pt D, Ch 3, Sec 1, where applicable.

4.2 Ship arrangement

4.2.1 Specific arrangement for livestock is to be as definedin NR467 Steel Ships, Pt D, Ch 3, Sec 2, [1].

4.3 Hull girder strength and hull scantlings

4.3.1 Hull girder strength

In general, the decks and platform decks above the strengthdeck used for the carriage of livestock may not be taken intoaccount for the calculation of the section modulus.

4.3.2 Movable or collapsible structural elements above the strength deck

In general, the movable or collapsible structural elementsabove the strength deck used for the stocking and the distri-bution of livestock on decks or platform decks are not a partof ship classification.

5 Bulk carriers

5.1 Application

5.1.1 Ships having one of the service notations bulk carrierESP or bulk carrier are to comply with the requirements ofthe present Article and with the requirement of NR467 SteelShips, Pt D, Ch 4, Sec 1.

5.1.2 As a rule, the hull structure of ships whose servicenotation is completed by the additional service feature non-homoload as defined in NR467 Steel Ships, Pt A, Ch 4, Sec 3,[3.1.2], is to be checked according to NR467 Steel Ships, PartB instead of the present Rules.


5.2.1 Specific ship arrangement is to comply with require-ments defined in NR467 Steel Ships, Pt D, Ch 4, Sec 2.


5.3.1 Structure design principles defined in NR467 SteelShips, Pt D, Ch 4, Sec 3, [2], are applicable.

5.4 Design loads

5.4.1 ApplicationIn addition to the requirements of Chapter 3, the loadingconditions, subdivided into departure and arrival condi-tions, defined in NR467 Steel Ships, Pt D, Ch 4, Sec 3,[3.1.2] are applicable.

The loading conditions are to be used for hull girderstrength and local strength.

5.4.2 Additional requirements on local loads for ships with the additional service feature heavycargo

For ships with a service notation completed by the addi-tional service feature heavycargo [AREA1, X1 kN/m2 -AREA2, X2 kN/m2 - ...] (see NR467 Steel Ships, Pt A, Ch 1,Sec 2, [4.2.2]) the values of pDB used to calculate the dryuniform cargo as defined in Ch 3, Sec 4, [3.2.2], in kN/m2,are to be specified by the Designer for each AREAi, andintroduced as Xi values in the above service feature.

5.4.3 Loading conditions for primary structure analysis

The following loading conditions are to be considered inthe analysis of the primary structure:

• homogeneous loading and corresponding draught T

• heavy ballast (the ballast hold being full) and corre-sponding draught T.

FW Y, FT i, FY wind i,,+( )i 1=

i N=

=


NR 600, Ch 5, Sec 4

5.5 Hull scantlings

5.5.1 PlatingAs a rule, the minimum thickness, in mm, for the followingplatings, is to be not less than:

a) side plating located between hopper and topside tanks:

tMIN = L0,5 + 2

b) inner bottom plating in holds:

tMIN = 2,15 (LWL1/3 k) + 4,4 s + 2

where:s : Length, in m, of the shorter side of the plate

panel.



5.5.3 Secondary stiffenersThe thicknesses of side frames and their brackets, in way ofcargo holds, are to be not less than the values given in Tab 2.

Table 2 : Minimum thickness ofside frames and brackets

5.5.4 Scantlings of side frames adjacent to the collision bulkhead

The scantlings of side frames in way of the foremost cargohold and immediately adjacent to the collision bulkheadare to be increased by 25% with respect to those deter-mined according to Chapter 4, in order to prevent excessiveimposed deformation on the side shell plating.

As an alternative, supporting structures are to be fittedwhich maintain the continuity of fore peak girders withinthe foremost cargo hold.

5.6 Hatch covers

5.6.1 Steel large hatch covers are to be as defined inNR467 Steel Ships, Pt D, Ch 4, Sec 4.

5.7 Protection of hull metallic structure

5.7.1 Protection of cargo hold is to be as defined in NR467Steel Ships, Pt D, Ch 4, Sec 3, [7].


5.8.1 Construction and testing are to fulfil the requirementsof NR467 Steel Ships, Pt D, Ch 4, Sec 3, [8].

6 Ore carriers

6.1 Application

6.1.1 Ships having the service notation ore carrier are tocomply with the requirements of the present Article and ofNR467 Steel Ships, Pt D, Ch 5, Sec 1, where applicable.

6.1.2 As a rule, for ships having alternate light and heavycargo loading conditions, the hull scantlings are to bechecked according to NR467 Steel Ships, Part B instead ofthe present Rules.


6.2.1 Specific ship arrangement is to comply with therequirements defined in NR467 Steel Ships, Pt D, Ch 5, Sec 2.


6.3.1 Structure design principle defined in NR467 SteelShips, Pt D, Ch 5, Sec 3, [3] are applicable.

6.4 Design loads


The loading conditions are to be used for hull girderstrength and local strength.

6.4.2 Loading conditions for primary structure analysis

The following loading conditions are to be considered inthe analysis of the primary structure:

• full load and scantling draught T, the loaded holds beingcompletely filled with cargo

• full load, the cargo density being equal to the maximumdensity of cargoes without taken less than 3t/m3, andscantling draught T

• ballast condition and ballast draught corresponding tothis condition (the ballast draught may be taken equal to0,04 L if this value is unknown).

6.5 Hull scantlings

6.5.1 Minimum thickness of the inner bottom plating in holds


As a rule, the minimum thickness, in mm, of the inner bot-tom plating in holds is not to be less than:

tMIN = 2,15 (LWL1/3 k) + 4,4 s + 2

where:

s : Length, in m, of the shorter side of the platepanel.

Item Minimum thickness, in mm

Side frame webs

9,7 + 0,03 LWL

Lower end bracket

The greater of the following:• 11,7 + 0,03 LWL

• as fitted thickness of side frame web

Upper end bracket

The greater of the following:• 9,7 + 0,03 LWL

• as fitted thickness of side frame web


NR 600, Ch 5, Sec 4

6.5.2 Strength checks of cross-ties analysed through a three dimensional beam analysis

Cross-tie analysis is to be carried out as defined in NR467Pt D, Ch 5, Sec 3, [5.2].

6.6 Hatch covers

6.6.1 Steel large hatch covers are to be as defined inNR467 Steel Ships, Pt D, Ch 4, Sec 4 for hatch covers ofships having the service notation ore carrier.


6.7.1 Construction and testing are to fulfil the requirementsof NR467 Steel Ships, Pt D, Ch 5, Sec 3, [7].

7 Combination carriers

7.1 Application

7.1.1 Ships having the service notation combination car-rier are to comply with the requirements of the present Arti-cle and with the requirements of NR467 Steel Ships, Pt D,Ch 6, Sec 1, where applicable.

7.1.2 As a rule, for ships having alternate light and heavycargo loading conditions, the hull scantlings are to bechecked according to NR467 Steel Ships, Part B instead ofthe present Rules.




7.3.1 Structure design principles defined in NR467 SteelShips, Pt D, Ch 6, Sec 3, [3] and Pt D, Ch 6, Sec 3, [4] areapplicable for ships having the service notation combina-tion carrier/OBO ESP and combination carrier/OOC ESPrespectively.

7.4 Design loads


7.4.2 Oil cargo mass densityIn the absence of more precise values, an oil cargo mass den-sity of 0,9 t/m3 is to be considered for calculating the internalpressures and forces in cargo tanks according to Ch 3, Sec 4.

7.5 Hull scantlings

7.5.1 PlatingAs a rule, the thickness of the plating of the inner bottom inholds intended to carry ore, of the strength deck and ofbulkheads is to be not less than the values given in Tab 3.

Table 3 : Minimum plating thickness


The thickness of the web of secondary stiffeners is to be notless than the value obtained, in mm, from the following for-mula:

tMIN = 0,75 L1/3 k + 4,5 s + 3

where s is the spacing, in m, of secondary stiffeners.


a) Minimum thickness:

The thickness of plating which forms the webs of pri-mary supporting members is to be not less than thevalue obtained, in mm, from the following formula:

tMIN = 1,45 L1/3 k + 3

b) Strength check of primary structure through a three-dimensional beam model:

Where the primary structure is checked through a threedimensional beam model, the following requirements ofNR467 Steel Ships are to be applied:

• Pt D, Ch 6, Sec 3, [6.3.2] for floors of cargo tankwith hopper tank

• Pt D, Ch 6, Sec 3, [6.3.3] for cross-ties

• Pt D, Ch 6, Sec 3, [6.3.4] for cross-ties when a finiteelement model is carried out.

7.5.4 Strength check with respect to stresses due to the temperature gradient

Direct calculations of stresses induced in the hull structuresby the temperature gradient are to be performed for shipsintended to carry cargoes at temperatures exceeding 90°C.In these calculations, the water temperature is to beassumed equal to 0°C.

The calculations are to be submitted to the Society forreview.




7.6.2 Machinery space and opening arrangement are to bein accordance with the requirements of NR467 Steel Ships,Pt D, Ch 6, Sec 3, [7].

Plating Minimum thickness, in mm

Strength deck (5,5 + 0,02 L) k1/2 + 1,5

Inner bottom in holds intended to carry ore

2,15 (L1/3 k) + 4,5 s + 2

Tank bulkhead L1/3 k + 4,5 s + 2

Watertight bulkhead 0,85 L1/3 k + 4,5 s + 1

Note 1:s : Length, in m, of the shorter side of the plate panel


NR 600, Ch 5, Sec 4

7.7 Hatch covers

7.7.1 Steel large hatch covers are to be as defined inNR467 Steel Ships, Pt D, Ch 4, Sec 4 for hatch covers ofships having the service notation ore carrier.

7.8 Protection of hull metallic structures

7.8.1 Requirements of NR467 Steel Ships, Pt D, Ch 6, Sec 3,[9] are applicable.

7.9 Cathodic protection of tanks




8 Oil tankers and FLS tankers

8.1 Application

8.1.1 Ships having the service notation oil tanker or FLStanker are to comply with the requirements of the presentArticle and of NR467 Steel Ships, Pt D, Ch 7, Sec 1, whereapplicable.

8.1.2 As a rule, for ships having non homogeneous loadingconditions, the hull scantlings are to be checked accordingto NR467 Steel Ships, Part B instead of the present Rules.



8.3 Design loads

8.3.1 Application

In addition to the requirements of Chapter 3, the loadingconditions, subdivided into departure and arrival condi-tions, defined in NR467 Steel Ships, Pt D, Ch 7, Sec 3,[3.1.1] are applicable.

8.3.2 Cargo mass density

In the absence of more precise values, a cargo mass densityof 0,9 t/m3 is to be considered for calculating the internalpressures and forces in cargo tanks according to Ch 3, Sec 4.

8.3.3 Partial filling

The carriage of cargoes with a mass density above the oneconsidered for the design of the cargo tanks may be allowedwith partly filled tanks under the conditions stated in theNR467 Steel Ships, Pt B, Ch 5, Sec 6, [2]. The classificationcertificate or the annex to this certificate is to mention theseconditions of carriage.

8.3.4 Overpressure due to cargo filling operationsFor ships having the additional service feature asphalt car-rier, the overpressure which may occurred under loading/unloading operations are to be considered, if any. In such acase, the diagram of the pressures in loading/unloadingconditions is to be given by the Designer.

8.3.5 Loading conditions for primary structureThe loading conditions for the analysis of primary structureare to be as defined in NR467 Steel Ships, Pt D, Ch 7, Sec 3,[4.3.2].

8.4 Hull scantlings

8.4.1 PlatingThe thickness of the strength deck and bulkhead plating isto be not less than the values given in Tab 4.


8.4.2 Secondary stiffenersThe thickness of the web of secondary stiffeners is to be notless than the value obtained, in mm, from the following for-mula:

tMIN = 0,75 L1/3 k + 4,5 s + 1


8.4.3 Primary stiffenersa) Minimum thickness

The thickness of plating which forms the webs of pri-mary supporting members is to be not less than thevalue obtained, in mm, from the following formula:

tMIN = 1,45 L1/3 k + 1

b) Strength check of primary structure through a threedimensional beam modelWhere the primary structure is checked through a threedimensional beam model, the following requirements ofNR467 Steel Ships are to be applied:• Pt D, Ch 7, Sec 3, [4.3.3] for floors of cargo tank

with hopper tank• Pt D, Ch 7, Sec 3, [4.3.4] for cross-ties• Pt D, Ch 7, Sec 3, [4.3.5] for cross-ties when a finite

element model is carried out.



The calculations are to be submitted to the Society for review.

Plating Minimum thickness in mm

Strength deck (5,5 + 0,02 L) k1/2 + 1,5

Tank bulkhead L1/3 k1/6 + 4,5 s + 1

Watertight bulkhead 0,85 L1/3 k1/6 + 4,5 s + 1



NR 600, Ch 5, Sec 4


8.5.1 Machinery space and opening arrangement are to bein accordance with the requirements of NR467 Steel Ships,Pt D, Ch 7, Sec 3, [5].



8.7 Cathodic protection of tanks




9 Chemical tankers

9.1 Application

9.1.1 Ships having the service notation chemical tanker areto comply with the requirements of the present Article and ofNR467 Steel Ships, Pt D, Ch 8, Sec 1, where applicable.

9.2 Ship survival capability and location of cargo tanks

9.2.1 See NR467 Steel Ships, Pt D, Ch 8, Sec 2.



9.4 Cargo containment

9.4.1 Cargo containmenta) Structure design principles

• Material of tanks, rubber and synthetic materialsliner are to be in accordance with NR467 SteelShips, Pt D, Ch 8, Sec 4, [1.1]

• Corrugated bulkhead connections are to be in com-pliance with NR467 Steel Ships, Pt D, Ch 8, Sec 4,[1.3].

b) Hull girder loads

• In addition to the requirements of Chapter 3, theloading conditions defined in NR467 Steel Ships, PtD, Ch 7, Sec 3, [2] are applicable.

c) Scantling of integral tanks• The thickness of the strength deck and bulkhead plat-

ing is to be not less than the values given in Tab 5• The calculation of the equivalent thickness for clad

plates made of non-alloyed steel-stainless steel is tobe carried out as defined in NR467 Steel Ships, Pt D,Ch 8, Sec 4, [3.1.2]

• The thickness of the web of secondary stiffeners is tobe not less than the value obtained, in mm, from thefollowing formula:

tMIN = 0,75 L1/3 k + 4,5 s + 2

where s is the spacing, in m, of secondary stiffeners

• The thickness of plating which forms the webs of pri-mary supporting members is to be not less than thevalue obtained, in mm, from the following formula:

tMIN = 1,45 L1/3 k + 2

• Where the cargo tank structure with hopper tank ischecked through a three dimensional beam model,the requirements of NR467 Steel Ships, Pt D, Ch 8,Sec 4, [3.3.3] are to be applied.

d) Scantling of independent tanks

Scantlings of independent tank structure are to bechecked as defined in NR467 Steel Ships, Pt D, Ch 8,Sec 4, [4].

e) Supports of independent tanks

Supports of independent tanks are to be checked asdefined in NR467 Steel Ships, Pt D, Ch 8, Sec 4, [5].



9.5.1 Machinery space is to be in accordance with therequirements of NR467 Steel Ships, Pt D, Ch 8, Sec 4, [6].





10 Tankers

10.1 Application

10.1.1 Ships having the service notation tanker are to com-ply with the requirements of the present Article and ofNR467 Steel Ships, Pt D, Ch 10, Sec 1, where applicable.

10.1.2 As a rule, for ships having non homogeneous load-ing conditions, the hull scantlings are to be checkedaccording to NR467 Steel Ships, Part B.


Strength deck (5,5 + 0,02 L) k1/2 + 1,5





NR 600, Ch 5, Sec 4


10.2.1 Specific ship arrangement is to comply with therequirements defined in NR467 Steel Ships, Pt D, Ch 10,Sec 2, [1].

10.3 Design loads

10.3.1 Application

In addition to the requirements of Chapter 3, the loadingconditions, subdivided into departure and arrival condi-tions, defined in NR467 Steel Ships, Pt D, Ch 7, Sec 3,[3.1.1] are applicable.

10.4 Hull scantlings

10.4.1 Plating

The thickness of the strength deck and bulkhead plating isto be not less than the values given in Tab 6.



The thickness of the web of secondary stiffeners is to be notless than the value obtained, in mm, from the following for-mula:

tMIN = 0,75 L1/3 k + 4,5 s + 2



The thickness of plating which forms the webs of primarysupporting members is to be not less than the valueobtained, in mm, from the following formula:

tMIN = 1,45 L1/3 k + 2

10.4.4 Structure in way of the connection between the tank and the hull structure

The tanks are to be locally strengthened in way of their con-nection to the hull structure and of their securing points, ifany.

The structure of the ship is to be strengthened so as to avoidexcessive deformations, due to the weight of the full tanksand inertia forces caused by motions of the ship, specifiedin Chapter 3.



The calculations are to be submitted to the Society forreview.


10.5.1 Machinery space is to be in accordance with therequirements of NR467 Steel Ships, Pt D, Ch 10, Sec 2,[6.1].

11 Passenger ships

11.1 Application

11.1.1 Ships having the service notation passenger ship areto comply with the requirements of the present Article andof NR467 Steel Ships, Pt D, Ch 11, Sec 1, where applicable.


11.2.1 Specific ship arrangement is to comply with therequirements defined in NR467 Steel Ships, Pt D, Ch 11,Sec 2.

11.3 Design loads

11.3.1 Bow impact pressure

The bow impact pressure is to be calculated, in kN/m2, asdefined in NR467, Pt D, Ch 11, Sec 3, [3.1.1].


11.4.1 Plating

If a complete deck does exist at a distance from the free-board deck exceeding 2 times the standard height of super-structures as defined in Ch 1, Sec 1, the thickness of the sideshell plating located between this complete deck and thestrength deck may be taken not greater than the thickness ofdeckhouse sides defined in Sec 1.


11.5.1 Side doors and stern doors

Side doors may be either below or above the free boarddeck.

Stern doors are to be situated above the freeboard deck.

The structure and arrangement of side doors and stern doorsare to be as defined in Sec 2, [5].


Strength deck (5,5 + 0,02 L) k1/2 + 1,5





NR 600, Ch 5, Sec 4

12 Ro-ro passenger ships

12.1 Application

12.1.1 Ships having the service notation ro-ro passengership are to comply with the requirements of the presentArticle and of NR467 Steel Ships, Pt D, Ch 12, Sec 1, whereapplicable.




12.3.1 Specific structure design principles are to complywith the requirements defined in NR467 Steel Ships, Pt D,Ch 12, Sec 2.

12.4 Design loads

12.4.1 Wheeled loads

The wheeled loads induced by vehicles are defined in Ch 3,Sec 4, [3.3].

12.4.2 Lowest 0,5 m of bulkheads forming vertical division along escape route in accommodation

The still water and inertial pressures transmitted to the struc-tures belonging to lowest 0,5 m of bulkheads and other par-titions forming vertical divisions along escape routes are tobe obtained, in kN/m2, as specified in Ch 3, Sec 4, [4.2],where the value pS is to be taken not less than 1,5 kN/m2 toallow them to be used as walking surfaces from the side ofthe escape route with the ship at large angles of heel.


12.5.1 Plating

If a complete deck does exist at a distance from the free-board deck exceeding 2 times the standard height of super-structures as defined in Ch 1, Sec 1, the thickness of the sideshell plating located between this complete deck and thestrength deck may be taken not greater than the thickness ofdeckhouse sides defined in Sec 1.

The thickness of plating subjected to wheeled loads is to beobtained according to Ch 4, Sec 3.


The scantling of secondary stiffeners subjected to wheeledloads is to be obtained according to Ch 4, Sec 4.


The scantling of primary stiffeners subjected to wheeledloads is to be obtained according to Ch 4, Sec 4.


12.6.1 Superstructure and deckhouseRequirements defined in NR467 Steel Ships, Pt D, Ch 12,Sec 3, [6.1] are applicable.

12.6.2 Bow doors and inner doorsThe requirements applicable to bow doors and inner doorsare defined in Sec 2, [4].

12.6.3 Side doors and stern doorsSide doors may be either below or above the free boarddeck.

Stern doors are to be situated above the freeboard deck.

The structure and arrangement of side doors and stern doorsare to be as defined in Sec 2, [5].

12.6.4 Movable deck, inner ramps and external ramps

The requirements defined in Sec 2, [7] are applicable.

13 Tugs

13.1 Application

13.1.1 Ships having one of the service notations tug, sal-vage tug, escort tug or anchor handling vessel are to com-ply with the requirements of the present Article and ofNR467 Steel Ships, Pt D, Ch 14, Sec 1, where applicable. Note 1: The general scope of application of these service notationsis defined in NR467 Steel Ships, Pt D, Ch 14, Sec 2, [1].


13.2.1 Specific structure design principles are to complywith the requirements defined in NR467 Steel Ships, Pt D,Ch 14, Sec 2, [2.3].


13.3.1 GeneralThe scantlings of plating, secondary stiffeners and primarystiffeners are to be in accordance with Chapter 4, where thehull girder loads and the local loads are defined in Chapter3, to be calculated for a moulded draught T not less than0,85 D.

13.3.2 Side platingThe thickness of the side plating is to be increased by 1 mmwith respect to that calculated according to Ch 4, Sec 3,without being taken greater than that of the adjacent bottomplating calculated for the same panel dimensions.


13.4.1 The following element of structure are to be inaccordance with NR467 Steel Ships, Pt D, Ch 14, Sec 2,[2.5]:

• machinery casings

• emergency exits from machinery space

• height of hatchway coamings.


NR 600, Ch 5, Sec 4

13.4.2 Rudder and bulwarks

a) Rudder

The rudder stock diameter is to be increased by 5% withrespect to that calculated according to Sec 2, [8].

b) Bulwarks

The bulwarks are to be sloped inboard to avoid distor-tions likely to occur during contact. Their height may bereduced where required by operational necessities.

13.4.3 Fenders

Fenders are to be fitted at the deck level on the ship side,extending on the whole length of the ship.

13.5 Towing arrangements

13.5.1 The towing arrangements are to be in accordancewith NR467 Steel Ships, Pt D, Ch 14, Sec 2, [2.8].


13.6.1 Requirements of NR467 Steel Ships, Pt D, Ch 14,Sec 2, [2.9] are applicable.

13.7 Additional requirements for salvage tugs, for escort tugs and for anchor handling vessels

13.7.1 The requirements of NR467 Steel Ships, Pt D, Ch 14,Sec 2 are applicable to salvage tugs, escort tugs and anchorhandling vessels.

13.8 Integrated tug/barge combination

13.8.1 The requirements defined in NR467 Steel Ships, PtD, Ch 14, Sec 3 are applicable to integrated tug/barge com-bination.

14 Supply vessels

14.1 Application

14.1.1 Ships having the service notation supply vessel areto comply with the requirements of the present Article andwith the requirements of NR467 Steel Ships, Pt D, Ch 15,Sec 1, where applicable.


14.2.1 Specific ship arrangement is to comply with therequirements defined in NR467 Steel Ships, Pt D, Ch 15,Sec 2, [2].

14.3 Access arrangement

14.3.1 Access arrangement for supply vessels with addi-tional service feature LHNS or WS is to comply with therequirements defined in NR467 Steel Ships, Pt D, Ch 15,Sec 2, [2].


14.4.1 Specific structure design principles are to complywith the requirements defined in NR467 Steel Ships, Pt D,Ch 15, Sec 2, [5].

14.5 Design loads

14.5.1 Dry uniform cargoesThe still water and inertial pressures transmitted to the struc-ture of the upper deck intended to carry loads are to beobtained, in kN/m2, as specified in Ch 3, Sec 4, [3.2.1],where the value of pS is to be taken not less than 24 kN/m2.


14.6.1 PlatingThe thickness of the side and upper deck plating is to be notless than the values given in Tab 7.


Within the cargo area, the thickness of strength deck platingis to be increased by 1,5 mm with respect to that deter-mined according to Ch 4, Sec 3.


a) Longitudinally framed side exposed to bumping

In the whole area where the side of the supply vessel isexposed to bumping, the section modulus of secondarystiffeners is to be increased by 15% with respect to thatdetermined according to Ch 4, Sec 4.

b) Transversely framed side exposed to bumping

In the whole area where the side of the supply vessel isexposed to bumping, the section modulus of secondarystiffeners, i.e. side, ‘tweendeck and superstructureframes, is to be increased by 25% with respect to thatdetermined according to Ch 4, Sec 4.

14.6.3 Primary stiffenersIn the whole area where the side of the supply vessel isexposed to bumping, a distribution stringer is to be fitted atmid-span, consisting of an intercostal web of the same heightas the secondary stiffeners, with a continuous face plate.

The section modulus of the distribution stringer is to be atleast twice that calculated in [14.6.2] for secondary stiffeners.

Side frames are to be fitted with brackets at ends.

Within reinforced areas, scallop welding for all side sec-ondary stiffeners is forbidden.


Side below freeboard deck

The greater value obtained from:• 3,1 + 0,031 L k0,5 + 4,5 s• 8 k0,5 + 1

Side between freeboard deck and strength deck

The greater value obtained from:• 3,1 + 0,013 L k0,5 + 4,5 s• 8 k0,5 + 1

Upper deck 7


NR 600, Ch 5, Sec 4

14.7 Other structure

14.7.1 Aft partAft part structure is to be in accordance with NR546 SteelShips, Pt D, Ch 15, Sec 2, [8.1].

14.7.2 Superstructures and deckhouses

a) Deckhouses

Due to their location at the forward end of the supplyvessel, deckhouses are to be reduced to essentials andspecial care is to be taken so that their scantlings andconnections are sufficient to support wave loads.

b) The thickness of forecastle aft end plating and of platingof deckhouses located on the forecastle deck is to be notless than the values given in Tab 8.

c) Secondary stiffeners

The section modulus of secondary stiffeners of the fore-castle aft end and of deckhouses located on the forecas-tle deck is to be not less than the values obtained fromTab 9.

Secondary stiffeners of the front of deckhouses locatedon the forecastle deck are to be fitted with brackets attheir ends. Those of side and aft end bulkheads of deck-houses located on the forecastle deck are to be weldedto decks at their ends.

Table 8 : Minimum thickness ofdeckhouses located on the forecastle deck

Table 9 : Minimum section modulus of deckhouse secondary stiffeners located on the forecastle deck

14.7.3 Arrangement for hull and forecastle openingsThe arrangement for hull and forecastle openings are tocomply with the requirements of NR467 Steel Ships, Pt D,Ch 15, Sec 2, [8.3].

14.7.4 Structure of cargo tanksScantling of cargo tanks is to be in compliance with the pro-visions of Chapter 3 and Chapter 4.

Design details are defined in NR467 Steel Ships, Pt D, Ch 15,[4] to Pt D, Ch 15, [7].

14.8 Hull outfitting

14.8.1 RuddersRudders are to comply with the requirements of NR467Steel Ships, Pt D, Ch 15, Sec 2, [9.1].

14.8.2 Bulwarks staysThe bulwark stays are to be designed with an attachment tothe deck able to withstand an accidental shifting of deckcargo (e.g. pipes).

14.8.3 Chain lockerChain lockers are to be arranged as gas-safe areas. Hullpenetrations for chain cables and mooring lines are to bearranged outside the hazardous areas.

Note 1: Hazardous area is an area in which an explosive atmos-phere is or may be expected to be present in quantities such as torequire special precautions for the construction, installation anduse of electrical apparatus.

15 Fire-fighting ships

15.1 Application

15.1.1 Ships having the service notation fire-fighting shipare to comply with the requirements of the present Articleand with the requirements of NR467 Steel Ships, Pt D, Ch15, Sec 1, where applicable.


15.2.1 Hull structureThe strengthening of the structure of the ships, where neces-sary to withstand the forces imposed by the fire-extinguish-ing systems when operating at their maximum capacity inall possible directions of use, are to be considered by theSociety on a case-by-case basis.

15.2.2 Water and foam monitorsThe seatings of the monitors are to be of adequate strengthfor all modes of operation.


15.3.1 Arrangement for hull and superstructure openings

On ships which are not fitted with a water-spraying systemcomplying with NR467 Steel Ships, Pt D, Ch 16, Sec 4, [3],all windows and port lights are to be fitted with efficientdeadlights or external steel shutters, except for the wheel-house.

16 Oil recovery ships

16.1 Application

16.1.1 Ships having the service notation oil recovery shipare to comply with the requirements of the present Articleand of NR467 Steel Ships, Pt D, Ch 15, Sec 1, where appli-cable.


16.2.1 Specific ship arrangement is to comply with therequirements defined in NR467 Steel Ships, Pt D, Ch 17,Sec 2, [1.2].

Structure PlatingMinimum thickness,

in mm

Deckhouses locatedon the forecastle deck

front 5,8 + 0,014 L

sides 5,2 + 0,014 L

StructureSecondary

stiffeners onSection modulus,

in cm3

Deckhouses located on the forecastle deck

front plating3 times the value calculated according to Sec 1, [4]

side plating0,75 times the value for the forecastle ‘tweendeck frames


NR 600, Ch 5, Sec 4


16.3.1 Additional loadsAdditional loads defined in NR467 Steel Ships, Pt D, Ch 17,Sec 2, [3] are to be taken into account.


16.4.1 TestingTests are to be carried out according to a specification sub-mitted by the interested Party, in order to check the properoperation of the oil recovery equipment.

These tests may be performed during dock and sea trials.

17 Cable-laying ships

17.1 Application

17.1.1 Ships having the service notation cable laying shipare to comply with the requirements of the present Articleand of NR467 Steel Ships, Pt D, Ch 18, Sec 1, where appli-cable.


17.2.1 Cable tanksThe scantlings of cable tanks are to be obtained throughdirect calculations carried out according to NR467 SteelShips, Pt B, Ch 7, App 1, where the still water and wave loadsare to be calculated for the most severe condition of use.

17.2.2 Connection of the machinery and equipment with the hull structure

The scantlings of the structures in way of the connectionbetween the hull structure and the machinery and equip-ment, constituting the laying or hauling line for submarinecables, are to be obtained through direct calculation carriedout according to NR467 Steel Ships, Pt B, Ch 7, App 1,based on the service loads of such machinery and equip-ment, as specified by the Designer.

In calculating these above service loads, the Designer is totake into account the inertial loads induced by ship motionsin the most severe condition of use.


17.3.1 Fore partIn general, a high freeboard is needed in the forward area,where most repair work is carried out, in order to provideadequate safety and protection against sea waves.

17.4 Equipment

17.4.1 Hawse pipeHawse pipes are to be integrated into the hull structure insuch a way that anchors do not interfere with the cable laying.

17.4.2 SheavesWhere there is a risk that, in rough sea conditions, sheavesare subjected to wave impact loads, special solutions suchas the provision of retractable type sheaves may be adopted.

18 Non-propelled units

18.1 Application

18.1.1 Non-propelled ships having the service notationbarge, pontoon or pontoon-crane are to comply with therequirements of the present Article and of NR467 SteelShips, Pt D, Ch 19, Sec 1, where applicable.

18.1.2 General requirements defined in NR467 Steel Ships,Pt D, Ch 19, Sec 2, [1] are applicable.


18.2.1 Specific structure design principles defined inNR467 Steel Ships, Pt D, Ch 19, Sec 2, [3] are applicable.

18.3 Hull girder strength

18.3.1 Non-propelled units lifted by crane

For non-propelled units intended to be lifted on board shipby crane, the hull girder strength is to be checked, in thecondition of fully-loaded barge lifted by crane, through cri-teria to be agreed with the Society on a case-by-case basis.

18.3.2 Ships with service notation pontoon carrying special cargoes

For ships with the service notation pontoon intended for thecarriage of special cargoes, such as parts of offshore units,the hull girder strength is to be checked through criteria tobe agreed with the Society on a case-by-case basis.

Moreover, where these ships are fitted with arrangementsfor launching the above structures, additional calculationsare to be carried out in order to evaluate the stresses duringthe various stages of launching. The Society may acceptstresses higher than those defined in Ch 2, Sec 3, to be con-sidered on a case-by-case basis, taking into account favour-able sea and weather conditions during launching.


18.4.1 General

a) Minimum thickness of ships with service notation bargecarrying liquids

For ships with the service notation barge carrying liquidcargo inside tanks, the thicknesses of cargo tank platingsare to be not less than the values given in Tab 10.

For other structures or transverse bulkheads not formingboundaries of cargo tanks, the above minimum thick-nesses may be reduced by 1 mm.

In pump rooms, the thicknesses of plating of exposeddecks, longitudinal bulkheads and associated secondarystiffeners and primary supporting members are to be notless than the values given in Tab 10.

b) Minimum thicknesses of decks forming tank top

Where the decks of non-propelled units form a tank top,the minimum thicknesses of plating are to be not lessthan those obtained from Tab 10.


NR 600, Ch 5, Sec 4

c) Thickness of strength deck plating

Within the cargo area, the thickness of strength deckplating is to be increased by 1,5 mm with respect to thatcalculated according to Ch 4, Sec 3.

Table 10 : Minimum thickness of plating

18.4.2 Hull scantlings of non-propelled units with the service notation pontoon fitted with arrangements and systems for launching operations

a) Additional information

In addition to the documentation specified in Ch 1, Sec 1,[7], the following information is to be submitted to theSociety:

• maximum draught of the ship during the differentstages of the launching operations

• operating loads and their distribution

• launching cradle location.

b) Scantlings of plating, secondary and primary stiffeners

In applying the formulae in Chapter 4, T is to be takenequal to the maximum draught during the differentstages of launching and taking into account, whereappropriate, the differential static pressure.

c) Deck scantlings

The scantlings of decks are to be in accordance withChapter 4, considering the maximum loads acting onthe launching cradle.

The thickness of deck plating in way of launch groundways is to be suitably increased if the cradle may beplaced in different positions.

The scantlings of decks in way of pivoting and end areasof the cradle are to be obtained through direct calcula-tions, to be carried out according to the criteria inNR467 Steel Ships, Pt B, Ch 7, App 1.

d) Launching cradles

The launching cradles are to be adequately connectedto deck structures and arranged, as far as possible, inway of longitudinal bulkheads or at least of girders.

18.4.3 Hull scantlings of non-propelled units with service notation pontoon-crane

Requirements defined in NR467 Steel Ships, Pt D, Ch 19,Sec 2, [5.3] are applicable.


18.5.1 Equipment

a) Manned non-propelled units

The equipment of anchors, chain cables and ropes to befitted on board manned non-propelled units is to com-ply with Sec 5.

Chain cables for anchors may be replaced by steel ropeshaving the same breaking load. The ropes are to be con-nected to the anchors by approximately 10 m of chaincable complying with Sec 5.

Non-propelled units continuously assisted by a tug mayhave only one anchor, complying with Sec 5, and achain rope having length neither less than 75% of thelength obtained according to Sec 5, nor less than220 m.

b) Unmanned non-propelled units

For unmanned non-propelled units, the equipment isnot required for classification purposes. The scantlingsof anchors, chain cables and ropes to be fitted on boardare the responsibility of the Designer.

c) Towing arrangements

Non-propelled units are to be fitted with suitablearrangements for towing, with scantlings under theresponsibility of the Designer.

The Society may, at the specific request of the interestedparties, check the above arrangements and the associ-ated hull strengthening; to this end, the maximum pullfor which the arrangements are to be checked is to bespecified on the plans and documents submitted forapproval.

19 Fishing vessels

19.1 Application

19.1.1 Ships having the service notation fishing vessel areto comply with the requirements of the present Article andof NR467 Steel Ships, Pt D, Ch 20, Sec 1, where applicable.



19.3 Hull scantling

19.3.1 PlatingThe thickness of bottom, side and deck plating is to beincreased by 0,5 mm with respect to that calculated accord-ing to Chapter 4.

19.4 Specific design loads

19.4.1 GeneralThe specific design loads defined in the present Article areto be taken into account in addition to the design loadsdefined in Chapter 3.


Decks, sides, bottom, inner bottom, bulkheads, primary supporting members in the cargo area

• for L ≤ 45 m:(4,1 + 0,060 L) k0,5 + 1

• for L > 45 m:(5,9 + 0,023 L) k0,5 + 1

Weather deck, within cargo area outside 0,4 L amidships

11,3 s k0,5 + 1

Web of secondary stiffeners and other structures of cargo tanks

• for L ≤ 45 m:(4,1 + 0,060 L) k0,5 + 1

• for L > 45 m:(5,9 + 0,023 L) k0,5 + 1



NR 600, Ch 5, Sec 4

19.4.2 Fish hold

The design pressure pF, in kN/m2, to be considered for thescantling of fish holds, is to be obtained from the followingformula:

where:

zTOP : Z co-ordinate of the highest point of the fishhold, in m

z0 : Z co-ordinate of the lowest point of the fishhold, in m

z : Z co-ordinate of the calculation point, in m

hTD : ‘Tweendeck height, in m.

In all cases, this pressure is to be taken not less than10 kN/m2.

19.4.3 Lower deck

The design pressure pLD, in kN/m2, to be considered for thescantling of lower decks is to be obtained from the follow-ing formulae:

• for working deck:

pLD = 8,5

• for cargo ‘tweendeck:

pLD = 7 hTD, to be taken not less than 10 kN/m2

where:

hTD : ‘Tweendeck height, in m.

19.4.4 Dry uniform cargoes on decks

The design pressure transmitted to the deck structures is ingeneral defined by the Designer; in any case, it may not betaken less than 10 kN/m2.


19.5.1 Plating minimum thickness

As a rule, the thickness of platings is to be not less than theminimum values given in Tab 11.

19.5.2 Bottom structure

a) Keel

The cross-sectional area, in cm2, of vertical solid barkeels made of forged or rolled, is to be not less than:

S = (0,4 + 10 T/L) (1,5 L − 9) n2 k

The value of T/L is to be taken neither less than 0,050nor more than 0,075.

The thickness, in mm, of solid bar keel is to be not lessthan:

t = (5 + 0,7 L k1/2) n2 cT

b) Open floors in transversely framed double bottom

Open floors are to be arranged in accordance with Ch 4,Sec 5, [3.2].

The section modulus, in cm3, of open floors is not to beless than the one of bottom secondary stiffeners forframes and the one of inner bottom secondary stiffenersfor reverse frames.

When open floors are connected by struts, the sectionmodulus is to be calculated according to Ch 4, Sec 4,[1.5.2].


19.5.3 Side structure

In the engine room of transversely framed ships, the sectionmodulus of web frames is not to be less than four times thatof adjacent frames.

The web height is not to be less than twice that of adjacentframes.

19.5.4 Deck structure

a) Plating thickness of strength deck

In addition to thickness requirements of strength deckplating defined in Ch 4, Sec 3, the thickness of strengthdeck plating is to be not less than:

• for two-deck ships without large openings, the lowervalue of the following formulae:

t = 2 s (2 L − 50)1/2

t = 12 s

• for other ships:

t = 2 s (2 L − 50)1/2

b) Deck plating in way of masts and fishing devices

In way of masts and fishing devices, the deck thicknessin the reinforcement area is to be increased by 25%with respect to that obtained from the present Rules.

pF 7zTOP z–zTOP z0–---------------------- hTD=


Keel (5,6 + 0,028 L k1/2 + 5 s) n2 cT

Bottom: (2,8 + 0,032 L k1/2 + 5 s) n2 cT + 0,5

Inner bottom in the engine room

Thickness calculated according to Ch 4, Sec 3 increased by 1,5 mm

Side shell (2,8 + 0,032 L k1/2 + 5 s) n2 cT + 0,5

cT : Draught coefficient taken equal to:

cT may not be taken greater than 1,0n2 : Navigation coefficient to be taken equal to n1 as

defined in Ch 1, Sec 1, [3.1.1], excepted for nav-igation notation sheltered area where n2 = 0,85

cT 0 7 3TL-------+,= for L 25m≤

cT 0 85 2TL-------+,= for 25 m L 40m≤<

cT 1 0,= for L 40m>


NR 600, Ch 5, Sec 4

c) Working deck (between ramp and fishing gear)

The thickness of working deck plating, between the aftramp and the fishing gear, is to be increased by 1 mmwith respect to that obtained from the present Rules. Inany case, this thickness is to be not less than the mini-mum value in Tab 11.

d) Deck plating protected by wood sheathing or deck com-position

The thickness of deck plating protected by wood sheath-ing, deck composition or other arrangements deemedsuitable by the Society may be reduced by 10% withrespect to that obtained from the present Rules. In anycase, this thickness is to be not less than the minimumvalue in Tab 11.

19.5.5 Fish hold bulkheads

The fish hold bulkheads are to be checked according toChapter 4, taking into account the pressure defined in[19.4.2].

19.5.6 Aft ramp

a) Minimum thickness of the aft ramp and the lower part ofthe aft ramp side

As a rule, the thickness of plating of the aft ramp and thelower part of the aft ramp side is to be not less than12 mm.

b) Plating of the aft ramp and the lower part of the aft rampside

The thickness of plating of the aft ramp and the lowerpart of the aft ramp side is to be increased by 2 mm withrespect to that calculated according to the present Rulesfor side plating with the same plate panel dimensions.

c) Plating of the upper part of the aft ramp side

The thickness of plating of the upper part of the aft rampside is to be not less than the value calculated accordingto the present Rules for side plating with the same platepanel dimensions.

19.6 Lifting appliances and fishing devices

19.6.1 General

The fixed parts of lifting appliances and fishing devices,considered as an integral part of the hull, are the structurespermanently connected by welding to the ship’s hull (forinstance crane pedestals, masts, king posts, derrick heelseatings, etc., excluding cranes, derrick booms, ropes, rig-ging accessories, and, generally, any dismountable parts).The shrouds of masts embedded in the ship’s structure areconsidered as fixed parts.

19.6.2 Design loads

The design loads to be considered for the strength check ofmasts, fishing devices and reinforcements under decks are:

• the weights of booms and net hauling fittings

• the cargo loads, to be taken equal to the maximum trac-tion loads of the different lifting appliances, consideringthe rolling-up diameters defined here after.

The rolling-up diameters to be taken for the maximum trac-tion loads of the lifting appliances are for:

• the fishing winches: the mid rolling-up diameter

• the net winches: the maximum rolling-up diameter

• the winding-tackles: the minimum rolling-up diameter.

19.6.3 Strength check

The structure check of the reinforcements under decks sup-porting fishing devices, and to the strength check of fishingdevices and masts if welded to the deck is to be carried outby direct calculation.

Structural elements of masts, fishing devices and local rein-forcements under decks are to be checked by direct calcula-tions, taking into account the following permissible stresses:

a) for steel and aluminium structure:

σVM ≤ 0,5 R

where:

σVM : Von Mises equivalent stress, in N/mm2, tobe obtained as a result of direct calculations

R : Minimum yield stress for scantling criteria,in N/mm2, of the material, defined in Ch 1,Sec 2.

b) for composite structure:

SFfd = 1,4 SF

SFfd = 1,4 SFCS

where:

SF : Rules safety factor applicable to maximumstress defined in Ch 2, Sec 3, [3.2.1]

SFCS : Rules safety factor applicable to combinedstress defined in Ch 2, Sec 3, [3.2.2].

The buckling strength of the structural elements of mastsand fishing devices is to be checked in compliance withChapter 4.


19.7.1 Rudder stock scantlings

The rudder stock diameter is to be increased by 5% withrespect to that obtained from the formula in Sec 2, [8].

19.7.2 Propeller shaft brackets

Propeller shaft brackets are to be in accordance with Sec 2,[11].

For ships less than 30 m in length, single arm propeller shaftbrackets may be fitted.


NR 600, Ch 5, Sec 4

19.7.3 Equipment

The equipment in chain and anchor for ships having theservice notation fishing vessel is defined in Sec 5.

Equipment in anchors and cables defined in Sec 5 may bereduced on a case-by-case basis. Nevertheless, it belongs tothe Designer and/or shipyard to submit all the relevant infor-mation demonstrating that reduced equipment - its configura-tion - and all its components, fully copes with the anchoringforces most frequently encountered during service.

For ships of special design or for ships engaged in specialservices or on special voyage, the Society may consideranchoring equipment other than defined in the present Arti-cle and in Sec 5.

As an alternative to the stud link chain cables calculated inSec 5, [3.2], wire ropes may be used in the following cases:

• wire ropes for both the anchors, for ship’s length lessthan 30 m

• wire rope for one of the two anchors, for ship’s lengthbetween 30 m and 40 m.

The wire ropes above are to have a total length equal to 1,5times the corresponding required length of stud link chaincables, obtained from Sec 5, [3.2], and a minimum break-ing load equal to that given for the corresponding stud linkchain.

A short length of chain cable is to be fitted between the wirerope and the anchor, having a length equal to 12,5 m or thedistance from the anchor in the stowed position to thewinch, whichever is the lesser.

When chain cables are replaced by trawl warps, the anchoris to be positioned on the forecastle deck so that it may bereadily cast after it has been shackled to the trawl warp.Chocks or rollers are to be fitted at suitable locations, alongthe path of the trawl warps, between the winch and themooring chocks.


19.8.1 Protection of decks by wood sheathing

Before fitting the wood sheathing, deck plating is to be pro-tected with suitable protective coating.

The thickness of wood sheathing of decks is to be not lessthan:

• 65 mm, if made of pine

• 50 mm, if made of hardwood, such as teak.

The width of planks is not to exceed twice their thickness.

19.8.2 Protection of cargo sides by battens

In cargo spaces, where thermal insulation is fitted, battensformed by spaced planks are generally to be fitted longitudi-nally.

19.8.3 Deck composition

The deck composition is to be of such a material as to pre-vent corrosion as far as possible and is to be effectivelysecured to the steel structures underneath by means of suit-able connections.

20 Launch and seagoing launch

20.1 Application

20.1.1 Ships having the service notation launch or seago-ing launch are to comply with the requirements of thepresent Article.


20.2.1 Equipment

The attention of Shipowners is drawn to the fact that thesmaller a ship is, the more its provisions for mooring andanchoring may be reduced, and that these require to beadapted to the conditions of service most frequentlyencountered. They need to ensure in particular that thelength of anchor lines, the type of anchor, the length andnumber of mooring lines are appropriate to the placeswhere they anchor and moor, to the depth of water and thenature of the sea-bed, by supplementing the equipment ifneed be.

20.2.2 The equipment in anchors and chains is defined inSec 5.

20.2.3 On ships carrying two anchor chains of the pre-scribed length, the weight of the second anchor may bereduced by one third.

20.2.4 Ships with dynamic force FEN as defined in Sec 5less than 4,5 kN are not required to carry a second anchor,except in the case of passenger launch.

For ships with dynamic force FEN between 4,5 kN and 9 kN,the second anchor may also be dispensed with except forpassenger launch. In this case, the weight of the anchor is tobe increased by one third and the length and size of thechain cable are to correspond to the increased weight of theanchor as defined in Sec 5.

20.2.5 Anchoring gear comprising only 8 to 10 m of chainattached to each anchor, supplemented by hawsers of equiv-alent strength to the prescribed chain, may be accepted,subject to the agreement of the Shipowner and providedsuch arrangement does not contravene the National Regula-tions of the country whose flag the ship carries.

If such anchoring gear, with cables and reduced chains, isadopted, the weight of the second anchor is to be equal tothat of the first anchor as defined in Sec 5.


NR 600, Ch 5, Sec 5

SECTION 5 ANCHORING EQUIPMENT AND SHIPBOARD

FITTINGS FOR ANCHORING, MOORING AND

TOWING EQUIPMENT

Symbols

ReH : Minimum yield stress, in kN/m2, defined in Ch 1,Sec 2, [2]

R’lim : Minimum yield stress, in kN/m2, defined in Ch 1,Sec 2, [2].

1 Design assumption for anchoring equipment

1.1 General

1.1.1 The requirements of the present Section only apply totemporary anchoring of ships within a harbour or shelteredarea, where the ship is awaiting for berth, tide, etc.

1.1.2 The equipment complying with these requirements isnot designed to hold a ship off fully exposed coast in roughweather nor for stopping the ship which is moving or drift-ing. In these conditions, the loads on anchoring equipmentincrease to such a degree that its components can be dam-aged or lost.

1.1.3 For ships where frequent anchoring in open sea isexpected, Owner’s, shipyard’s and Designer’s attention isdrawn to the fact that anchoring equipment should be pro-vided in excess to the requirements of this Rules.

1.1.4 The equipment complying with the requirements in[3] is intended for holding a ship in good holding sea bot-tom, where the conditions are such as to avoid dragging ofthe anchor. In poor holding sea bottom, the holding powerof the anchors is significantly reduced.

1.1.5 Anchors and chains cable components and its accesso-ries, wire rope, etc. are to be manufactured in accordancewith relevant requirements of NR216 Materials and Welding.

1.1.6 The bow anchors, connected to their own chaincables, are to be so stowed as to always be ready for use.Other arrangements of equivalent provision in security andsafety may be foreseen, subjected to Society’s agreement.

1.2 General case

1.2.1 The determination of the anchoring equipment, asstipulated in [2], for ships having the navigation notationunrestricted navigation or coastal area is based on the fol-lowing assumptions:

• wind speed: 50 knots (25 m/s)

• current speed: 5 knots (2,5 m/s)

• the water depth for anchoring is approximately betweenone tenth and one sixth of the chain cable length calcu-lated according to [3.2.2], and

• the ship uses one anchor only under normal circum-stances.

1.3 Specific cases

1.3.1 Ships with navigation notation sheltered area

The determination of the anchoring equipment, as stipu-lated in [2], for ships having the navigation notation shel-tered area is to be based on the following assumptions:

• wind speed: 30 knots (15,5 m/s), and

• current speed: 5 knots (2,5 m/s).

1.3.2 Ships with service notation seagoing launch

The determination of the anchoring equipment, as stipu-lated in [2], for ships having the service notation seagoinglaunch is to be based on the following assumptions:

• wind speed: 27 knots (14 m/s), and


Specific arrangements are defined in Sec 4, [20].

1.3.3 Ships with service notation launch

The determination of the anchoring equipment, as stipu-lated in [2] for ships having the service notation launch is tobe based on the following assumptions:



Specific arrangements are defined in Sec 4, [20].

1.3.4 Ships with service notation ro-ro passenger ship or passenger ship

For ships having L ≤ 30 m, the service notation ro-ro pas-senger ship or passenger ship and a navigation notationother than unrestricted navigation, the determination of theanchoring equipment, as stipulated in [2], is to be based onthe following assumptions:




NR 600, Ch 5, Sec 5

1.3.5 Ships with service notation tug, salvage tug or escort tug

For ships having the service notation tug, salvage tug orescort tug, the determination of the anchoring equipment,as stipulated in [2], is to be based on the following assump-tions:



1.3.6 Fishing vessels having the navigation notation coastal area

For fishing vessels having the navigation notation coastalarea, the determination of the anchoring equipment, basedon the dynamic force FEN calculated as defined in [2], maybe reduced by 10%.

2 Anchoring equipment calculation

2.1 General

2.1.1 All ships are to be provided with equipment inanchors and chain cables (or cable and ropes) within thescope of classification. This equipment is determined fromthe dynamitic forces due to wind and current acting on theship in conditions as defined in [1].

2.1.2 For unmanned non-propelled units, the equipment isnot required for classification purposes. The scantlings ofanchors, chain cables and ropes to be fitted on board is theresponsibility of the Designer.

2.2 Anchoring force calculation for monohull

2.2.1 Dynamic force FEN

a) Dynamic force

The dynamic force FEN , in kN, induced by wind andcurrent acting on monohull in anchoring condition asdefined in [1.2.1] may be calculated as follows:

FEN = 2 (FSLPH + FSH + FSS)

where:

FSLPH : Static force on wetted part of the hull due tocurrent, as defined in [2.2.2]

FSH : Static force on hull due to wind, as definedin [2.2.3]

FSS : Static force on superstructures due to wind,as defined in [2.2.4].

b) Minimum value of the dynamic force

As a rule, the dynamic force FEN , in kN, is to be greaterthan:

• 7,0 for ships having the service notation tug, salvagetug or escort tug

• 2,2 for ships having the service notation fishing ves-sel

• 2,0 for ships having the service notation ro-ro pas-senger ship or passenger ship and a navigation nota-tion other than unrestricted navigation and L ≤ 30 m

• 1,0 for ships having the service notation seagoinglaunch or launch

• 6,5 in the other cases.

2.2.2 Static force on wetted part of hull FSLPH

The theoretical static force induced by current applied onthe wetted part of the hull, in kN, is defined according tothe following formula:

where:

ρ : Water density, equal to 1025 kg/m3

Cf : Coefficient equal to:

where:

Re : Reynolds number:

Re = V LWL / 1,054⋅10-6

k : Coefficient equal to:

Sm : Total wetted surface of the part of the hull underfull load draught, in m2

The value of Sm is to be given by the Designer.When this value is not available, Sm may betaken equal to 6 Δ2/3

V : Speed of the current, in m/s, as defined in [1].

2.2.3 Static force on hull FSH

The theoretical static force induced by wind applied on theupper part of the hull, in kN, is defined according to the fol-lowing formula:

where:

ρ : Air density, equal to 1,22 kg/m3

V : Speed of the wind, in m/s, as defined in [1]

Shfr : Front surface of hull, in m2, projected on a verti-cal plane perpendicular to the longitudinal axisof the ship

Shar : Aft hull transom surface, in m2, projected on avertical plane perpendicular to the longitudinalaxis of the ship

Shlat : Partial lateral surface of one single side of thehull, in m2, projected on a vertical plane paral-lel to the longitudinal axis of the ship anddelimited according to Fig 1

Chfr = 0,8 sin α, with α defined in Fig 1.

Note 1: In Fig 1, B is the breadth of the hull, in m.

FSLPH12---ρCfSmV210 3–=

Cf 1 k+( ) 0 075,Rlog e 2–( )2

------------------------------=

k 0 017, 20Cb

L2WL T 0.5– BWL

1.5–⋅------------------------------------------+=

FSH12---ρ ChfrShfr 0 2Shar, 0 02Shlat,+ +( )V210 3–=


NR 600, Ch 5, Sec 5

Figure 1 : Geometry of the upper part of the hull

2.2.4 Static force on superstructures FSS

The theoretical static force induced by wind applied on thesuperstructures, in kN, is defined according to the followingformula:

where:

ρ : Air density, equal to 1,22 kg/m3

V : Speed of the wind, in m/s, as defined in [1]

Ssfri : Front surface of a superstructure tier, in m2, pro-jected on a vertical plane perpendicular to thelongitudinal axis of the ship

Ssari : Aft surface of a superstructure tier, in m2, pro-jected on a vertical plane perpendicular to thelongitudinal axis of the ship

Sslati : Partial lateral surface of one single side of asuperstructure tier, in m2, projected on a verticalplane parallel to the longitudinal axis of the shipand delimited according to Fig 1

Csfri = 0,8 sin βi, with βi defined in Fig 1

Csari : Coefficient equal to:

• if hi/si ≥ 5,00: Csari = 0,7 sin γi

• if 5,00 > hi/si ≥ 0,25: Csari = 0,5 sin γi

• if hi/si < 0,25: Csari = 0,3 sin γi

where hi, si and γi are defined in Fig 1 for eachsuperstructure tier.

2.3 Anchoring force calculation for multihull

2.3.1 The dynamic force, in kN, induced by wind and cur-rent acting on multihull in anchoring condition as definedin [1.2.1] may be calculated as defined in [2.2] with the fol-lowing particular assumptions for the calculation of thestatic forces on the:

• wetted part of the hull

FSLPH : As defined in [2.2.2], taking into accountthe two floats for the calculation of the totalwetted surface Sm

• hull

FSH : As defined in [2.2.3], taking into account:

- the two floats for the calculation of Shfr

- the two floats transom and the aft sur-face of the aft transversal main beambetween the floats for the calculation ofShar

- one single side of one float for the calcu-lation of Shlat (“B” on Fig 1 is to be takenas the breadth of one float).

• superstructure

FSS : As defined in [2.2.4], taking also intoaccount the frontal surface of the platform.

3 Equipment in chain and anchor

3.1 Anchors

3.1.1 Mass of individual anchor

The individual mass of anchor, in kg, is to be at least equalto:

• P = (FEN / 7)⋅102 for ordinary anchor

• P = (FEN / 10)⋅102 for high holding power anchor

• P = (FEN / 15)⋅102 for very high holding power.

3.1.2 Number of anchors

As a rule, the number of anchors to be provided on board isto be at least:

a) General case

• one anchor, when the dynamic force FEN calculatedaccording to [2.2] is less than 4,5 kN (except forpassenger ships where 2 anchors are required)

• two anchors, when the dynamic force FEN calculatedaccording to [2.2] is between 4,5 kN and 45 kN

Note 1: For ships with FEN between 4,5 and 9,0 kN, the secondanchor may also be dispensed (except for passenger ships).In this case, the weight of the anchor and the length andsize of the chain cable are to be calculated according to[3.1.1], [3.2.1] and [3.2.2], considering FEN increased byone third.

��

��

��

��

��

��

��

�

FSS12---ρΣ Csfri

SsfriCsari

Ssari0 08Sslati

,+ +( )V210 3–=


NR 600, Ch 5, Sec 5

• three anchors, when the dynamic force FEN calcu-lated according to [2.2] is greater than 45 kN.

Note 2: In this case, two anchors are to be connected to their ownchain cables and positioned on board always ready to use.The third anchor is intended as a spare one and is notrequired for the purpose of classification.

b) Ships having L ≤ 30 m, the service notation ro-ro passen-ger ship or passenger ship and a navigation notationother than unrestricted navigation

• one anchor

c) Ships with service notation seagoing launch or launch

Ships with FEN less than 4,7 kN are not required to carrya second anchor, except in the case of passenger launch.

For ships with FEN between 4,7 kN and 9,0 kN, the sec-ond anchor may also be dispensed with, except for pas-senger launch. In this case, the weight of the anchor isto be increased by one third and the length and size ofthe chain cable are to correspond to the increasedweight of the anchor according to [3.2.2].

3.1.3 Anchor design and performance tests

Anchors are to be from an Approved Type. Therefore, Hold-ing power - performance - assessment, Design review andTests and examination on manufactured product are to becarried out.

Anchors are to have appropriate shape and scantlings incompliance with Society requirements. Moreover, they areto be constructed in compliance with the Society require-ments.

A high or very high holding power anchor is suitable for useon board without any prior adjustment or special placementon the sea bottom.

For approval and/or acceptance as a high or very high hold-ing power anchor, the anchor is to have a holding powerequal, respectively, to at least twice or four times that of aType Approved ordinary stockless anchor of the same mass.

Holding power is to be assessed by full-scale comparativetests.

For very high holding power anchors, the holding powertest load is to be less than or equal to the proof load of theanchor, specified in NR216 Materials and Welding, Ch 4,Sec 1, [1.5.2].

Comparative tests on Type Approved Ordinary stocklessanchors are to be carried out at sea and are to provide satis-factory results on various types of seabeds.

Alternatively sea trials by comparison with a previouslyapproved HHP anchor may be accepted as a basis forapproval.

Such tests are to be carried out on anchors whose massesare, as far as possible, representative of the full range ofsizes proposed for the approval.

At least two anchors of different sizes are to be tested. Themass of the greatest anchor to be approved is not to be inexcess of 10 times that of the maximum size tested and themass of the smallest is to be not less than 0,1 times that ofthe minimum size tested.

Tests are normally to be carried out by means of a tug, but,alternatively, shore-based tests may be accepted.

The length of the chain cable connected to the testedanchor, having a diameter appropriate to its mass, is to besuch that the pull acting on the shank remains practicallyhorizontal. For this purpose a scope of chain cable equal to10 is deemed normal; however lower values may beaccepted.

Three tests are to be carried out for each anchor and type ofsea bottom. Three are the types of sea bottoms in whichtests are to be performed, e.g. soft mud or silt, sand or graveland hard clay or similar compounded.

The pull is to be measured by means of a dynamometer;measurements based on the bollard pull against propeller'srevolutions per minute curve may be accepted instead ofdynamometer readings.

Anchor stability and its ease of dragging are to be noteddown, whenever possible.

Upon satisfactory outcome of the above tests, the Societywill issue a certificate declaring the compliance of high orvery high holding power anchors with its relevant Rules.

3.1.4 Manufacturing, materials, test and examinationManufacturing and materials are to comply with the rele-vant requirements of NR216 Materials and Welding.Tests and examination requirements are to comply withNR216 Materials and Welding, Ch 4, Sec 1, [1.5].

3.2 Chain cables

3.2.1 Stud link chain cable scantlingChain cable diameter, type and steel grades are to be asdefined in Tab 1, according to the minimum breaking loadBL and proof load PL, in kN, defined according to the fol-lowing formulae: • for steel grade Q1:

BL = 3 FEN

PL = 0,7 BL

• for steel grade Q2:

BL = 3,4 FEN

PL = 0,7 BL• for steel grade Q3:

BL = 3,75 FEN

PL = 0,7 BL

The chain cable scantling is to be consistent with the massof the associated anchor. In case the anchor on board isheavier by more than 7% from the mass calculated in[3.1.1], the value of FEN to take into account in the presentArticle for the calculation of BL and PL is to be deducedfrom the actual mass of the anchor according to the formu-lae in [3.1.1].

As a rule, the minimum diameter, in mm, corresponding toa quality Q1 is not to be less than:

• 11 in a general case• 7 for ships having L ≤ 30 m, the service notation ro-ro

passenger ship or passenger ship and a navigation nota-tion other than unrestricted navigation.


NR 600, Ch 5, Sec 5

Table 1 : Proof and breaking loads for stud link chain cables (quality Q)

3.2.2 Length of individual chain cable The length of chain cable Lcc, in m, linked to each anchor isto be at least equal to:

a) General case:Lcc = 30 ln(P) − 42

b) For ship having the service notation tug, salvage tug orescort tug:Lcc = 0,15 P + 40

where:P : Anchor weight, in kg, defined in [3.1.1] for an

ordinary anchor according to the consideredcase.

The minimum length of chain cable on board is to be inaccordance with the water depth of anchoring as specifiedin [1.2.1].

3.2.3 Chain cables arrangementsChain cables are to be made by lengths of 27,5 m each,joined together by Dee or lugless shackles.

Normally grade Q2 or Q3 for stud link chain cables andSL2 or SL3 for studless chain cables are to be used withHHP anchors. In case of VHHP anchors, grade Q3 or SL3chain cables are to be used.

The method of manufacture of chain cables and the charac-teristics of the steel used are to be approved by the Societyfor each manufacturer. The material from which chaincables are manufactured and the completed chain cablesthemselves are to be tested in accordance with the appro-priate requirements.

Test and examination requirements are to comply withNR216 Materials and Welding, Ch 4, Sec 1.

3.2.4 Studless link chain cablesFor ships with FEN less than 18 kN, studless short link chaincables may be accepted by the Society as an alternative tostud link chain cables, provided the equivalence in strengthis determined according to Tab 2 on the basis of proof loadsdefined for steel grade Q in [3.2.1].

3.3 Wire ropes and synthetic fibre ropes

3.3.1 As an alternative to the chain cable, wire ropes orsynthetic fibre ropes may be used in the following cases:

• for both anchors, for ship length less than 30 m

• for one of the two anchors, for ship length between30 m and 40 m.

The ropes are to have a length equal to 1,5 times the chaincable length as calculated in [3.2.2].

A short length of chain cable having scantlings complyingwith [3.2] is to be fitted between the rope and the bowanchor. The length of this chain part is not to be less than12,5 m or the distance from the anchor to its stowed posi-tion to the windlass, whichever is the lesser.

Fibre ropes are to be made of polyamide or other equivalentsynthetic fibres, excluding polypropylene.

The effective breaking load PR, in kN, of the rope is to benot less than the following value:

• PR = BL for wire rope

• PR = 1,2 BL for synthetic fibre rope,

where BL, in kN, is the required breaking load defined in[3.2.1] of the replaced chain cable.

Chain diameter(mm)

Grade Q1 Grade Q2 Grade Q3 Minimum mass per meter length

(kg/m)Proof load

(kN)Breaking load (kN)

Proof load(kN)

Breaking load (kN)

Proof load(kN)

Breaking load (kN)

11,0 36 51 51 72 72 102 2,7

12,5 46 66 66 92 92 132 3,6

14,0 58 82 82 115 115 165 4,4

16,0 75 107 107 150 150 215 5,7

17,5 89 128 128 180 180 255 6,7

19,0 105 150 150 210 210 300 7,9

20,5 123 175 175 244 244 349 9,1

22,0 140 200 200 280 280 401 10,5

24,0 167 237 237 332 332 476 12,4

26,0 194 278 278 389 389 556 14,5

28,0 225 321 321 449 449 649 16,7

30,0 257 368 368 514 514 735 19,2

32,0 291 417 417 583 583 833 21,9

34,0 328 468 468 655 655 937 24,7

36,0 366 523 523 732 732 1050 27,6

38,0 406 581 581 812 812 1160 30,9

40,0 448 640 640 896 896 1280 33,8


NR 600, Ch 5, Sec 5

Table 2 : Proof and breaking loads for studless link chain cable (quality SL)

3.4 Attachment pieces

3.4.1 Both attachment pieces and connection fittings forchain cables are to be designed and constructed in suchway as to offer the same strength as the chain cable and areto be tested in accordance with the appropriate require-ments.

4 Shipboard fittings for anchoring equipment

4.1 Windlass and chain stopper

4.1.1 Windlass

The windlass is to be power driven and suitable for the sizeof chain cable and/or ropes when applicable.

The windlass is to be fitted in a suitable position in order toensure an easy lead of the chain cable to and through thehawse pipe; the deck, at the windlass, is to be suitably rein-forced.

The windlass is to be provided with a brake having suffi-cient capacity to stop chain cable and anchor where payingout, even in the event of failure of the power supply.

Windlass and brake have to be designed and workshoptested to withstand the following pull exerted on the cable-lifter without any permanent deformation of the stressedparts and without brake slip:

• 0,8 times the breaking load BL of the chain (defined in[3.2.1]) if not combined with a chain stopper

• 1,2 times the value of FEN (defined in [2.2.1]) if com-bined with a chain stopper.

4.1.2 Chain stopper

A chain stopper may be fitted between the windlass and thehawse pipe in order to relieve the windlass of the pull of thechain cable when the ship is at anchor.

A chain stopper with all its parts is to be capable of withstand-ing a pull of 0,8 times the value of the chain breaking loadBL (defined in [3.2.1]; the deck at the chain stopper is to besuitably reinforced.

Chain tensioners or lashing devices supporting the weightof the anchor where housed in the anchor pocket are not tobe considered as chain stoppers.

Where the windlass is at a distance from the hawse pipeand no chain stopper is fitted, suitable arrangements are tobe provided to lead the chain cable to the windlass.

Chain diameter (mm)

Grade SL1 Grade SL2 Grade SL3 Minimum mass per meter length

(kg/m)Proof load

(kN)Breaking load (kN)

Proof load(kN)

Breaking load (kN)

Proof load(kN)

Breaking load (kN)

6,0 6.5 13 9 18 13 26 0,8

8,0 12 24 17 34 24 48 1,4

10,0 18.5 37 26 52 37 74 2,4

11,0 22.5 45 32 64 45 90 2,7

12,5 29 58 41 82 58 116 3,5

14,5 39 78 55 110 78 156 4,6

16,0 47.5 95 67 134 95 190 5,6

17,5 56.5 113 80 160 113 226 6,8

19,0 67 134 95 190 134 268 7,9

20,5 78 156 111 222 156 312 9,3

22,0 90 180 128 256 180 360 10,6

24,0 106 212 151 302 212 424 12,7

25,5 120 240 170 340 240 480 14,3

27,0 135 270 192 384 270 540 16,1

28,5 150 300 213 426 300 600 17,9

30,0 166 332 236 472 332 664 19,8

32,0 189 378 268 536 378 756 22,5

33,0 201 402 285 570 402 804 24,0

35,0 226 452 321 642 452 904 27,0

37,0 253 506 359 718 506 1012 30,2

38,0 267 534 379 758 534 1068 32,0

40,0 296 592 420 840 592 1184 35,2


NR 600, Ch 5, Sec 5

4.1.3 Deck reinforcement under windlass and chain stopper

Local reinforcement of deck structure are to be provided inway of windlass and chain stopper, and designed in accord-ance with:

a) Windlass without chain stopper

• applied force as defined in [4.1.1], associated to:

- for steel and aluminium structure: the maximumpermissible stress equal to ReH or R’lim

- for composites materials structure: the minimumrule safety coefficient SF equal to 2.

b) Windlass combined with chain stopper

1) Windlass:


- for steel and aluminium structure: the maxi-mum permissible stress equal to 0,66ReH or0,66R’lim

- for composites materials structure: the mini-mum rule safety coefficient SF equal to 3.

2) Chain stopper:


- for steel and aluminium structure: the maxi-mum permissible stress equal to ReH or R’lim

- for composites materials structure: the mini-mum rule safety coefficient SF equal to 2.

4.2 Chain locker

4.2.1 The chain locker is to be of a capacity adequate tostow all chain cable equipment and provide an easy directlead to the windlass.

Where two anchor lines are fitted, the port and starboardchain cables are to be separated by a bulkhead in the locker.

The inboard ends of chain cables are to be secured to thestructure by a fastening able to withstand a force not lessthan 15% nor more than 30% of the breaking load of thechain cable.

In an emergency, the attachments are to be easily releasedfrom outside the chain locker.

Where the chain locker is arranged aft of the collision bulk-head, its boundary bulkheads are to be watertight and adrainage system provided.

4.3 Anchoring sea trials

4.3.1 General

The anchoring sea trials are to be carried out on board inthe presence of a Society surveyor according to the presentArticle.

4.3.2 Single windlass arrangement

The test is to demonstrate that the windlass complies withthe requirements given in [4.1] particularly that it worksadequately and has sufficient power to simultaneouslyweigh the two anchors - excluding the housing in the housepipe - where both are suspended to a 55 m of chain cable innot more than 6 min.

4.3.3 One windlass per anchoring line arrangement

Where two windlasses operating separately on each chaincable are adopted, the weighing test is to be carried out forboth, weighing an anchor suspended to 82,5 m of chaincable and verifying that the time required for the weighing -excluding the housing on the hawse pipe - does notexceeds 9 min.

4.3.4 The brake is to be tested during lowering operations.

5 Shipboard fittings for towing and mooring

5.1 General

5.1.1 The equipment for mooring and or towing are notcovered within the scope of classification.

However, deck reinforcements under mooring and towingequipment such as, bitts, bollard, fairleads, chocks... are tobe examined within the scope of hull drawing examination.

For ships of 500 GT and above, the requirements of NR467Pt B, Ch 9, Sec 4, [5] are to be applied, considering anequivalent equipment number EN equal to five times thevalue of FEN as calculated in [2.2.1].

5.1.2 Documents to be submitted

Maximum safe working loads of equipment used for themooring and the towing are to be specified.

A mooring and towing arrangement plan is to be submittedto the Society for information. This plan is to define themethod of use the mooring and towing lines and to includethe equipment location on the deck, the fitting type, the safeworking loads and the manner of applying mooring andtowing lines (including line angles).

5.1.3 Hull structure reinforcement

As a general rule, hull structure reinforcements in way ofmooring and towing equipment are to be examined bydirect calculation, taking into account:

• a tension in the mooring or towing line equal to the safeworking load of the equipment, and

• the permissible stresses and safety coefficients asdefined in Ch 2, Sec 3.

Note 1: When the mooring plan is not available, the equipmentsuch as bitts and bollards (when the line may come and go from thesame direction) are to be loaded up to twice their safe workingloads.


NR 600, Ch 5, Sec 5


NR 600

Chapter 6

CONSTRUCTION AND TESTING

SECTION 1 GENERAL

SECTION 2 WELDING FOR STEEL

SECTION 3 TESTING

SECTION 4 CONSTRUCTION SURVEY


NR 600, Ch 6, Sec 1


SECTION 1 GENERAL

1 General

1.1

1.1.1 The present Chapter contains the requirements con-cerning the welding, welds and assembling of structure, andthe testing and construction survey.

2 Welding, welds and assembly of structure

2.1 Material

2.1.1 The scantling and joint design of welded connectionfor ships built in steel materials are defined in Sec 2.

2.1.2 The equivalent requirements for ships built in alumin-ium alloys are defined in NR561 Aluminium Ships.

The conditions for heterogeneous assembly between steeland aluminium structures are also to be as defined inNR561 Hull in Aluminium Alloys.

2.1.3 The scantling of joint assembly for ships built in com-posite materials are to be as defined in NR546 CompositeShips.

3 Testing

3.1 General

3.1.1 The testing conditions for tanks, watertight andweathertight structures for ships built in steel, aluminiumand composite materials are define in Sec 3.

4 Construction survey

4.1 General

4.1.1 The requirements for hull construction and surveywithin the scope of classification and/or certification ofships hulls are defined in: • For steel ship: in Sec 4• For aluminium ship: in the NR561 Aluminium Ships• For composite ship: in the NR546 Composite Ships.

NR 600, Ch 6, Sec 2

SECTION 2 WELDING FOR STEEL

1 General

1.1 Materials

1.1.1 The requirements of the present Section apply to thescantling and joint design of welded connection of shipsbuilt in steel materials.

1.2 Application

1.2.1 The scantling and preparation for the welding of steelhull structure are to be as defined in the present Section.

Other equivalent standards may be accepted by the Society,on a case-by-case basis.

The general requirements relevant to the execution of weld-ing, inspection and qualification of welding procedures aregiven in Chapter 5 of NR216 Rules on Materials and Welding.

1.2.2 Welding of various types of steel is to be carried outby means of welding procedures approved for the purpose.

1.2.3 Weld connections are to be executed according to:

• the approved hull construction plans, and

• the weld and welding booklets submitted to the Society.

Any details not specifically represented in the plans are, inany case, to comply with the applicable requirements of theSociety.

1.2.4 The method used to prepare the parts to be welded isleft to the discretion of each shipbuilder, according to itsown technology and experience.

These methods are to be reviewed during the qualificationof welding procedure, as defined in [1.3.2].

1.3 Weld and welding booklet

1.3.1 Weld booklet

A weld booklet, including the weld scantling such as throatthickness, pitch and design of joint, is to be submitted to theSociety for examination.

The weld booklet is not required if the structure drawingssubmitted to the Society contain the necessary relevant datadefining the weld scantling.

1.3.2 Welding booklet

A welding booklet including the welding procedures, oper-ations, inspections and the modifications and repair duringconstruction as defined in Sec 4, [3.4] is to be submitted tothe Surveyor for examination.

2 Scantling of welds

2.1 Butt welds

2.1.1 As a rule, all structural butt joints are to be full pene-tration welds completed by a backing run weld.

2.2 Butt welds on permanent backing

2.2.1 Butt welding on permanent backing may be acceptedwhere a backing run is not feasible.

In this case, the type of bevel and the gap between themembers to be assembled are to be such as to ensure aproper penetration of the weld on its backing.

2.3 Fillet weld on a lap-joint

2.3.1 General

Fillet weld in a lap joint may be used only for members sub-mitted to moderate stresses, taking into account the typicaldetails shown on Tab 1.

Continuous welding is generally to be adopted.

2.3.2 The surfaces of lap-joints are to be in sufficientlyclose contact.

2.4 Slot welds

2.4.1 Slot welding may be used where fillet welding is notpossible.

Slot welding is, in general, permitted only where stresses actin a predominant direction. Slot welds are, as far as possi-ble, to be aligned in this direction.

2.4.2 Slot welds are to be of appropriate shape (in generaloval) and dimensions, depending on the plate thickness,and may not be completely filled by the weld (see Tab 2).

The distance between two consecutive slot welds is to benot greater than a value which is defined on a case-by-casebasis taking into account:

• the transverse spacing between adjacent slot weld lines

• the stresses acting in the connected plates

• the structural arrangement below the connected plates.

2.5 Plug welding

2.5.1 Plug welding may be adopted exceptionally as a sub-stitute to slot welding.

Typical details are given in Tab 2.


NR 600, Ch 6, Sec 2

Table 1 : Typical lap joint (manual welding)

Table 2 : Plug and slot welding (manual welding)

2.6 Fillet weld

2.6.1 Fillet welding types

Fillet welding may be of the following types:

• continuous fillet welding, where the weld is constitutedby a continuous fillet on each side of the abutting plate

• intermittent fillet welding, which may be subdividedinto:

- chain welding

- staggered welding.

2.6.2 Double continuous fillet weld location

As a general rule, double continuous fillet weld is to berequired in the following locations, as appropriate:

• boundaries of watertight plates

• primary and secondary stiffeners with the attached platingat end connections or in way of brackets (end connectionmeans the length extending over 20% of span at ends)

• flange with web of built-up stiffeners at end connec-tions, in way of brackets, in way of flange knuckle andin way of rounded of face plate

• main engine and auxiliary machinery seatings

• bottom structure of high speed ship in way of jet roomspaces

• bottom structure in way of propeller blade

• structure in way of bilge keel, stabilizer, bow thruster,cranes,...

Detail Standard Remark

Fillet weld in lap joint

b = 2 t2 + 25 mm

location of lap joint to be

approved by the Society

Fillet weld in joggled lap joint

b ≥ 2 t2 + 25 mm

Detail Standard

Plug welding • t ≤ 12 mm = 60 mmR = 6 mm40° ≤ θ ≤ 50°G = 12 mmL > 2

• 12 mm < t ≤ 25 mm = 80 mmR = 0,5 t mmθ = 30°G = t mmL > 2

Slot welding • t ≤ 12 mmG = 20 mm = 80 mm

2 ≤ L ≤ 3 , max 250 mm

• t > 12 mmG = 2 t = 100 mm

2 ≤ L ≤ 3 , max 250 mm

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NR 600, Ch 6, Sec 2

Continuous fillet weld may also be adopted in lieu of inter-mittent welding wherever deemed suitable, and it is recom-mended where the length p, defined according to [2.6.5], islow.

2.6.3 Throat thickness of double continuous fillet weld

The minimum throat thickness tT of a double continuous filletweld, in mm, is to be obtained from the following formula:

where:

wF : Welding factor for the various hull structuralelements, defined in Tab 3

t : Actual thickness, in mm, of the thinner plate ofthe assembly

tTmin : Minimum throat thickness, in mm, taken equalto:

• tTmin = 3,0 mm, where the thickness of thethinner plate is less than 6 mm

• tTmin = 3,5 mm, otherwise.

The throat thickness tT may be increased for particular load-ing conditions.

2.6.4 Direct calculation of double continuous fillet weld

Where deemed necessary, the minimum throat thickness tTof a double continuous fillet weld between stiffener weband associated plating and/or flange, in mm, may be deter-mined as follows:

where:

T : Shear force, in N, in the considered section ofthe stiffener

I : Inertia, in mm4, of the stiffener

τ : Permissible shear stress, in N/mm2, as defined inCh 2, Sec 3

tTmin : Minimum throat thickness defined in [2.6.3]

m : Value, in mm3, calculated as follows (see Fig 1):

• for weld between flange and web:

m = tf bf vf

• for weld between associated plate and web:

m = tp bp vp

2.6.5 Throat thickness of intermittent weld

The throat thickness tIT, in mm, of intermittent welds is to benot less than:

where:

tT : Throat, in mm, of the double continuous filletweld, obtained as defined in [2.6.3]

p, d : As defined as follows:

• chain welding (see Fig 2):

d ≥ 75 mm

p − d ≤ 200 mm

• staggered welding (see Fig 3):

d ≥ 75 mm

p − 2 d ≤ 300 mm

p ≤ 2 d for connections subjected to highalternate stresses.

Note 1: In general, staggered welding is not allowed for connec-tions subjected to high alternate stresses.

2.6.6 Fillet weld in way of cut-outs

The throat thickness of the welds between the cut-outs inprimary supporting member webs for the passage of sec-ondary stiffeners is to be not less than the value obtained, inmm, from the following formula:

where:

tT : Throat thickness defined in [2.6.3]

ε, λ : Dimensions, in mm, to be taken as shown in Fig 4.

Figure 1 : Stiffener elements definition for m calculation

Figure 2 : Intermittent chain welding

Figure 3 : Intermittent staggered welding

tT wFt tTmin≥=

tTTm2Iτ-------- tTmin≥ ≥

tIT tTpd---=

tTC tTελ---=

tp

tf

bf

vf

Neutralaxis

vp

tT

tT

bp


NR 600, Ch 6, Sec 2

Table 3 : Welding factor wF for the various hull structural connections

Hull areaConnection

wF (1)of to

General, unless otherwise

specified in the Table

watertight plates boundaries 0,35

non-tight plates boundaries 0,20

strength decks side shell 0,45

webs of secondary stiffen-ers

plating 0,13

plating at ends (2) 0,20

web of primary stiffener see [2.6.7]

web of primary stiffeners plating and flange 0,20

plating and flange at ends (2) 0,30 (3)

bottom and inner bottom (in way of transverse and/or longitudinal bulkhead supported on tank top)

0,45

deck (for cantilever deck beam) 0,45

web of primary stiffeners 0,35

Structures located abaft 0,25 L from the fore end

secondary stiffeners bottom and side shell plating 0,20

primary stiffeners bottom, inner bottom and side shell plating 0,25

Structures located in bottom slamming area

or in the first third of the platform bottom of cata-

maran

secondary stiffeners bottom plating 0,20

primary stiffeners bottom plating 0,25

Machinery space girders bottom and inner bottom plating

in way of main engine foundations

0,45

in way of seating of auxiliary machinery

0,35

elsewhere 0,25

floors (except in way of main engine foundations)

bottom and inner bottom plating

in way of seating of auxiliary machinery

0,35

elsewhere 0,25

floors in way of main engine foundations

bottom plating 0,35

foundation plates 0,45

floors centre girder single bottom 0,45

double bottom 0,25

Superstructures and deckhouses

external bulkheads deck 0,35

internal bulkheads deck 0,13

secondary stiffeners external and internal bulkhead plating 0,13

Pillars pillars deck pillars in compression 0,35

pillars in tension full penetration welding

Rudders primary element directly connected to solid parts or rudder stock

solid part or rudder stock 0,45

other webs each other 0,20

webs plating in general 0,20

top and bottom plates of rudder plating

0,35

(1) For connections where wF ≥ 0,35, continuous fillet welding is to be adopted.(2) Ends of secondary stiffeners means the length extending over 20% of span at ends. Where end brackets are fitted, end means

the area in way of brackets and at least 50 mm beyond the bracket toes. Where direct calculation are carried out, the end areais to be considered on a case-by-case basis.

(3) Full penetration welding may be required, depending on the structural design and loads.


NR 600, Ch 6, Sec 2

Figure 4 : Continuous fillet welding between cut-outs

2.6.7 Welding between secondary and primary stiffeners

As a general rule, the resistant weld section AW, in cm2, ofthe fillet weld connecting the secondary stiffeners to theweb of primary members, is not to be less than:

where:

ϕ : Coefficient as indicated in Tab 4

p : Design pressure, in kN/m2, acting on the sec-ondary stiffeners

s : Spacing of secondary stiffeners, in m

: Span of secondary stiffeners, in m

K : Greatest material factor of secondary stiffenerand primary member, as defined in Ch 1, Sec 2.

Table 4 : Coefficient ϕ

3 Typical joint preparation

3.1 General

3.1.1 The type of connection and the edge preparation areto be appropriate to the welding procedure adopted, thestructural elements to be connected and the stresses towhich they are subjected.

3.2 Butt welding

3.2.1 Permissible root gap between elements to be weldedand edge preparations are to be defined during qualificationtests of welding procedures and indicated in the weldingbooklet.

For guidance purposes, typical edge preparations and gapsare indicated in Tab 5.

Table 5 : Typical butt weld plate edge preparation(manual welding) - See Note 1

Case Weld ϕ

1Parallel to the reaction exertedon primary member

100

2Perpendicular to the reactionexerted on primary member

75

Throat a

ε

λ

AW ϕps 1 s2------–

K10 3–=

Detail Standard

Square butt

t ≤ 5 mmG = 3 mm

Single bevel butt

t > 5 mmG ≤ 3 mmR ≤ 3 mm50° ≤ θ ≤ 70°

Single vee butt

G ≤ 3 mm50° ≤ θ ≤ 70°R ≤ 3 mm

Double bevel butt

t > 19 mmG ≤ 3 mmR ≤ 3 mm50° ≤ θ ≤ 70°

Double vee butt, uniform bevels

G ≤ 3 mmR ≤ 3 mm50° ≤ θ ≤ 70°

Double vee butt, non-uniform bevels

G ≤ 3 mmR ≤ 3 mm6 ≤ h ≤ t/3 mmθ = 50°α = 90°

Note 1: Different plate edge preparation may be accepted orapproved by the Society on the basis of an appropriate weld-ing procedure specification.

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NR 600, Ch 6, Sec 2

3.2.2 In case of welding of two plates of different thicknessequal to or greater than:

• 3 mm, if the thinner plate has a thickness equal to orless than 10 mm, or

• 4 mm, if the thinner plate has a thickness greater than10 mm,

a taper having a length of not less than 4 times the differ-ence in thickness is to be adopted for connections of platingperpendicular to the direction of main stresses. For connec-tions of plating parallel to the direction of main stresses, thetaper length may be reduced to 3 times the difference inthickness.

When the difference in thickness is less than the above val-ues, it may be accommodated in the weld transitionbetween plates.

For large thicknesses (e.g. 25 mm), other criteria may be con-sidered on a case-by-case basis, when deemed equivalent.

3.2.3 Butt welding on backingFor butt welding on temporary or permanent backing, theedge preparations and gaps are to be defined by the ship-yard, taking into account the type of backing plate.

3.2.4 Section, bulbs and flat barsStiffeners contributing to the longitudinal or transversalstrength, or elements in general subject to high stresses, areto be connected together by butt joints with full penetrationweld. Other solutions may be adopted if deemed accepta-ble by the Society on a case-by-case basis.

The work is to be done in accordance with an approvedprocedure; in particular, this requirement applies to workdone on board or in conditions of difficult access to thewelded connection. Special measures may be required bythe Society.

3.3 Fillet weld

3.3.1 ClearanceIn fillet weld T connections, a gap g, as shown in Fig 5, notgreater than 2 mm may be accepted without increasing thethroat thickness calculated according to [2.6.3] to [2.6.6]as applicable.

In the case of a gap greater than 2 mm, the above throatthickness is to be increased.

In any event, the gap g may not exceed 4 mm.

Figure 5 : Gap in fillet weld T connections

3.3.2 Preparation and penetration of fillet weld

Where partial or full T penetration welding are adopted forconnections subjected to high stresses for which fillet weld-ing is considered unacceptable by the Society, typical edgepreparations are indicated in:

• for partial penetration welds: Fig 6 and Fig 7, in which f,in mm, is to be taken between 3 mm and T/3, and αbetween 45° and 60°

Figure 6 : Partial penetration weld

Figure 7 : Partial penetration weld

• for full penetration welds: Fig 8, in which f, in mm, is tobe taken between 0 and 3 mm, and α between 45° and60°.

Back gouging may be required for full penetrationwelds.

Figure 8 : Full penetration weld

3.3.3 Lamellar tearing

Precautions are to be taken in order to avoid lamellar tears,which may be associated with:

• cold cracking when performing T connections betweenplates of considerable thickness or high restraint

• large fillet welding and full penetration welding onhigher strength steels.

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NR 600, Ch 6, Sec 2

4 Plate misalignment

4.1 Misalignment in butt weld

4.1.1 Plate misalignment in butt connectionsThe misalignment m, measured as shown in Fig 9, betweenplates with the same thickness is to be less than 15% of theplate thickness without being greater than 3 mm.

Figure 9 : Plate misalignment in butt connections

4.2 Misalignment in cruciform connections

4.2.1 Misalignment in cruciform connectionsThe misalignment m in cruciform connections, measuredon the median lines as shown in Fig 10, is to be less thant/2, where t is the thickness of the thinner abutting plate.

The Society may require lower misalignment to be adoptedfor cruciform connections subjected to high stresses.

Figure 10 : Misalignment in cruciform connections


NR 600, Ch 6, Sec 3

SECTION 3 TESTING

1 General

1.1 Application

1.1.1 The following requirements determine the testingconditions for:

• gravity tanks, including independent tanks of 5 m3 ormore in capacity

• watertight or weathertight structures.

The purpose of these tests is to check the tightness and/orthe strength of structural elements.

1.1.2 Tests are to be carried out in the presence of the Sur-veyor at a stage sufficiently close to completion so that anysubsequent work would not impair the strength and tight-ness of the structure.

In particular, tests are to be carried out after air vents andsounding pipes are fitted.

1.1.3 The Society may accept that structural testing of a sis-ter ship is limited to a single tank for each type of structuralarrangement.

However, if the Surveyor detects anomalies, he may requirethe number of tests is increased or that the same number oftests is provided as for the first ship in a series.

1.2 Definitions

1.2.1 Shop primer

Shop primer is a thin coating applied after surface prepara-tion and prior to fabrication as a protection against corro-sion during fabrication.

1.2.2 Protective coating

Protective coating is a final coating protecting the structurefrom corrosion.

1.2.3 Structural testing

Structural testing is a hydrostatic test carried out to demon-strate the tightness of the tanks and the structural adequacyof the design. Where practical limitations prevail andhydrostatic testing is not feasible (for example when it is dif-ficult, in practice, to apply the required head at the top ofthe tank), hydropneumatic testing may be carried outinstead.

Structural testing is to be carried out according to [2.2].

1.2.4 Hydropneumatic testingHydropneumatic testing is a combination of hydrostatic andair testing, consisting in filling the tank to the top with waterand applying an additional air pressure.

Hydropneumatic testing is to be carried out according to[2.3].

1.2.5 Leak testingLeak testing is an air or other medium test carried out todemonstrate the tightness of the structure.

Leak testing is to be carried out according to [2.4].

1.2.6 Hose testingHose testing is carried out to demonstrate the tightness ofstructural items not subjected to hydrostatic or leak testingand of other components which contribute to the watertightor weathertight integrity of the hull.

Hose testing is to be carried out according to [2.5].

1.2.7 Sister shipA sister ship is a ship having the same main dimensions,general arrangement, capacity plan and structural design asthose of the first ship in a series, and built in the same ship-yard.

2 Watertight compartments

2.1 General

2.1.1 The requirements in [2.1] to [2.6] intend generally toverify the adequacy of the structural design of gravity tanks,excluding independent tanks of less than 5 m3 in capacity,based on the loading conditions which prevailed whendetermining the tank structure scantlings.

2.1.2 General requirements for testing of watertight com-partments are given in Tab 1, in which the types of testingreferred to are defined in [1.2].

2.2 Structural testing

2.2.1 Structural testing may be carried out before or afterlaunching.

2.2.2 Structural testing may be carried out after applicationof the shop primer.


NR 600, Ch 6, Sec 3

Table 1 : Watertight compartments - General testing requirements

Compartment orstructure to be tested

Type of testing Structural test pressure Remarks

Double bottom tanks Structural testing(1)

The greater of the following:• head of water up to the top of overflow• head of water up to the margin line (7)

Tank boundaries tested fromat least one side

Double side tanks Structural testing(1)

The greater of the following:• head of water up to the top of overflow• 2,4 m head of water above highest point of

tank (5)


Tank bulkheads, deep tanks Structural testing(1)

The greater of the following (2): • head of water up to the top of overflow• 2,4 m head of water above highest point of

tank (5) • setting pressure of the safety relief valves,

where relevant


Fuel oil bunkers Structural testing

Ballast holds of ships withservice notation bulk carrieror bulk carrier ESP

Structural testing(1)

The greater of the following:• head of water up to the top of overflow• 0,9 m head of water above top of hatch

Fore and after peaks used astank

Structural testing The greater of the following:• head of water up to the top of overflow• 2,4 m head of water above highest point of

tank (5)

Test of the after peak carriedout after the sterntube hasbeen fitted

Fore peak not used as tank Structural testing The greater of the following:• maximum head of water to be sustained in

the event of damage• head of water up to the margin line (7)

After peak not used as tank Leak testing

Cofferdams Structural testing(3)

The greater of the following:• head of water up to the top of overflow• 2,4 m head of water above highest point of

tank (5)

Watertight bulkheads Hose testing (4)

Watertight doors below free-board or bulkhead deck (6)

Structural testing Head of water up to the bulkhead deck Test to be carried out beforethe ship is put into service,either before or after thedoor is fitted on board

Double plate rudders Leak testing

Shaft tunnel clear of deeptanks

Hose testing

Shell doors Hose testing

Watertight hatch covers oftanks in ship with servicenotation bulk carrier or bulkcarrier ESP

Hose testing

Watertight hatch covers oftanks in ship with servicenotation combination carrierESP

Structural testing(1)

The greater of the following:• 2,4 m head of water above the top of hatch

cover• setting pressure of the safety relief valves,

where relevant

At least every second hatchcover is to be tested

Weathertight hatchcovers and closing appliances

Hose testing

Chain locker (if aft of collisionbulkhead)

Structural testing Head of water up to the top


NR 600, Ch 6, Sec 3

2.2.3 Structural testing may be carried out after the protec-tive coating has been applied, provided that one of the fol-lowing two conditions is satisfied:• all the welds are completed and carefully inspected vis-

ually to the satisfaction of the Surveyor prior to theapplication of the protective coating

• leak testing is carried out prior to the application of theprotective coating.

In the absence of leak testing, protective coating is to beapplied after the structural testing of:• all erection welds, both manual and automatic• all manual fillet weld connections on tank boundaries

and manual penetration welds.

2.3 Hydropneumatic testing

2.3.1 When a hydropneumatic testing is performed, theconditions are to simulate, as far as practicable, the actualloading of the tank.The value of the additional air pressure is at the discretionof the Society, but is to be at least as defined in [2.4.2] forleak testing.

The same safety precautions as for leak testing (see [2.4.2])are to be adopted.

2.4 Leak testing

2.4.1 An efficient indicating liquid, such as a soapy watersolution, is to be applied to the welds.

2.4.2 Where leak testing is carried out, in accordance withTab 1, an air pressure of 0,15⋅105 Pa is to be applied duringthe test.

Prior to inspection, it is recommended that the air pressurein the tank should be raised to 0,2⋅105 Pa and kept at thislevel for approximately 1 hour to reach a stabilised state,with a minimum number of personnel in the vicinity of thetank, and then lowered to the test pressure.

The test may be conducted after the pressure has reached astabilised state at 0,2⋅105 Pa, without lowering the pressure,provided the Society is satisfied of the safety of the person-nel involved in the test.

2.4.3 A U-tube filled with water up to a height correspond-ing to the test pressure is to be fitted to avoid overpressureof the compartment tested and verify the test pressure.

The U-tube is to have a cross-section larger than that of thepipe supplying air.

In addition, the test pressure is also to be verified by meansof one master pressure gauge.

Alternative means which are considered to be equivalentlyreliable may be accepted at the discretion of the Surveyor.

2.4.4 Leak testing is to be carried out, prior to the applica-tion of a protective coating, on all fillet weld connections ontank boundaries, and penetration and erection welds on tankboundaries excepting welds made by automatic processes.

Selected locations of automatic erection welds and pre-erection manual or automatic welds may be required to besimilarly tested to the satisfaction of the Surveyor, takingaccount of the quality control procedures operating in theshipyard.

For other welds, leak testing may be carried out after theprotective coating has been applied, provided that suchwelds have been carefully inspected visually to the satisfac-tion of the Surveyor.

Independent tanks Structural testing Head of water up to the top of overflow, but notless than 0,90 m

Ballast ducts Structural testing Ballast pump maximum pressure

(1) Hydropneumatic or leak testing may be accepted under the conditions specified in [2.3] and [2.4], respectively, provided thatat least one tank of each type is structurally tested, to be selected in connection with the approval of the design. In general,structural testing need not be repeated for subsequent ships of a series of identical new buildings. This relaxation does not applyto cargo space boundaries in ships with the service notation oil tanker ESP or combination carrier ESP and to tanks for segre-gated cargoes or pollutants. If the structural test reveals weakness or severe faults not detected by the leak test, all tanks are tobe structurally tested.

(2) Where applicable, the highest point of the tank is to be measured to deck and excluding hatches. In holds for liquid cargo orballast with large hatch covers, the highest point of tanks is to be taken at the top of the hatch.

(3) Hydropneumatic or leak testing may be accepted under the conditions specified in [2.3] and [2.4], respectively, when, at theSociety’s discretion, it is considered significant also in relation to the construction techniques and the welding proceduresadopted.

(4) When a hose test cannot be performed without damaging possible outfitting (machinery, cables, switchboards, insulation, etc...)already installed, it may be replaced, at the Society’s discretion, by a careful visual inspection of all the crossings and weldedjoints. Where necessary, a dye penetrant test or ultrasonic leak test may be required.

(5) For ships of less than 40 m in length, 2,4 m may be replaced by 0,3H with 0,9 ≤ 0,3 H ≤ 2,4, where H is the height of compart-ment, in m.

(6) The means of closure are to be subjected to a hose test after fitting on board.(7) The margin line is a line drawn at least 76mm below the upper surface of:

• the bulkhead deck at side for passenger ships• the freeboard deck at side for cargo ships

Compartment orstructure to be tested

Type of testing Structural test pressure Remarks


NR 600, Ch 6, Sec 3

2.4.5 Any other recognised method may be accepted to thesatisfaction of the Surveyor.

2.5 Hose testing

2.5.1 When hose testing is required to verify the tightnessof the structures, as defined in Tab 1, the minimum pressurein the hose, at least equal to 2,0⋅105 Pa, is to be applied at amaximum distance of 1,5 m.

The nozzle diameter is to be not less than 12 mm.

2.6 Other testing methods

2.6.1 Other testing methods may be accepted, at the dis-cretion of the Society, based upon equivalency considera-tions.

3 Miscellaneous

3.1 Watertight decks, trunks, etc.

3.1.1 After completion, a hose or flooding test is to beapplied to watertight decks and a hose test to watertighttrunks, tunnels and ventilators.

3.2 Doors in bulkheads above the bulkhead deck

3.2.1 Doors are to be designed and constructed as weath-ertight doors and, after installation, subjected to a hose testfrom each side for weathertightness.

3.3 Steering nozzles

3.3.1 Upon completion of manufacture, the nozzle is to besubjected to a leak test.

3.4 Working test of windlass

3.4.1 The working test of the windlass is to be carried outon board in the presence of a Surveyor.

3.4.2 The test is to demonstrate that the windlass complieswith the requirements of Ch 5, Sec 5 and, in particular, thatit works adequately and has sufficient power to simultane-ously weigh the two bower anchors (excluding the housingof the anchors in the hawse pipe) when both are suspendedto 55 m of chain cable, in not more than 6 min.

3.4.3 Where two windlasses operating separately on eachchain cable are adopted, the weighing test is to be carriedout for both, weighing an anchor suspended to 82,5 m ofchain cable and verifying that the time required for theweighing (excluding the housing in the hawse pipe) doesnot exceed 9 min.


NR 600, Ch 6, Sec 4

SECTION 4 CONSTRUCTION SURVEY

1 General

1.1 Scope

1.1.1 The purpose of this Section is to define hull construc-tion and survey requirements within the scope of the classi-fication of ships and/or certification of ship hulls built insteel materials.

Equivalent requirements are defined in:

• NR561 Aluminium Ships, for ships built in aluminium

• NR546 Composite Materials, for ships built in compos-ite materials

The scope of classification is defined in NR467 Steel Ships,Part A.

2 Structure drawing examination

2.1 General

2.1.1 The structure drawings submitted within the scope ofclassification and/or certification are to include the detailsof the welded connections between the main structural ele-ments, including throat thicknesses and joint types, as far asclass is concerned.

A weld booklet, as defined in Sec 2, [1.3.1] may berequested.

Note 1: For the various structural typical details of welded con-struction in shipbuilding and not dealt with in this Section, therules of good practice, recognized standards and past experienceare to apply as agreed by the Society.

2.1.2 Where several steel types are used, a plan showingthe location of the various steel types is to be submitted atleast for outer shell, deck and bulkhead structures.

3 Hull construction

3.1 Shipyard details and procedures

3.1.1 The following details are to be submitted by the Ship-yard to the Society:

• design office and production work staff

• production capacity (number of units per year, numberof types, sizes)

• total number of hull units already built.

3.1.2 The following procedures are to be submitted by theShipyard to the Society:

a) Traceability

• procedure to ensure traceability of materials, con-sumable and equipment covered by the Society’sRules (from the purchase order to the installation orplacing on ship)

• data to ensure traceability of the production means(describing the different steps such as inspection orrecording during production)

• handling of non-conformities (from the reception ofmaterials or equipment to the end of construction)

• handling of client complaints and returns to after-sales department.

b) Construction

• procedure to ensure that the hull is built in accord-ance with the approved drawings, as defined in [2]

• procedure to precise the equipment references, thereferences to any equipment approval, the suppliers'technical requirements, the precautions to be takenwhen installing the equipment

• builder’s inspection process and handling of defects

• procedure to ensure that the remedial measuresconcerning the defects and deficiencies noticed bythe Surveyor of the Society during the survey aretaken into account.

Procedures are also to define:

- the precautions to be taken to comply with thesuppliers and Society requirements in order notto cause, during installation, structure damagesaffecting structural strength and watertightness,and

- the preparations to be made on the hull in antic-ipation of installation.

3.2 Materials

3.2.1 The following details about materials used are to besubmitted by the Shipyard to the Society:

• list of steel types used for plates, stiffeners, filler productsetc., with their references and suppliers’ identification

• references of existing material approval certificates

• material data sheets containing, in particular, the suppli-ers’ recommendations on storage use.


NR 600, Ch 6, Sec 4

3.2.2 The storage conditions of materials and welding con-sumable are to be in accordance with the manufacturers’recommendations, in dry places without condensation andclear of the ground.

All the materials are to be identifiable in the storage site(type of steel and welding consumable, reference of batchesand type of approval certificate,...).

The builder is to provide an inspection to ensure that theincoming plates, stiffeners and consumable are in accord-ance with the purchase batches and that defective materialshave been rejected.

3.3 Forming

3.3.1 Forming operations are to be in accordance with thematerial manufacturer's recommendation or recognizedstandard.

3.4 Welding

3.4.1 Welding bookletA welding booklet, including the welding procedures, fillerproducts and the design of joints (root gap and clearance),as well as the sequence of welding provided to reduce to aminimum restraint during welding operations, is to be sub-mitted to the Surveyor for examination.

Moreover, the welding booklet is:

• to indicate, for each type of joint, the preparations andthe various welding parameters

• to define, for each type of assembly, the nature and theextent of the inspections proposed, in particular those ofthe non-destructive testing such as dye-penetrant testsand, if needed, those of the radiographic inspection.

3.4.2 Welding consumableThe various consumable materials for welding are to beused within the limits of their approval and in accordancewith the conditions of use specified in the respectiveapproval documents.

• Welding filler product

The choice of the welding filler metal is to be made tak-ing into account the welding procedure, the assemblyand the grade of steel corresponding to the parent metal

Welding filler products are generally to be approved bythe Society and are of type as defined in NR216 Materi-als and Welding, Ch 5, Sec 2 or of other types acceptedas equivalent by the Society.

• Welding consumable and welding procedures adoptedare to be approved by the Society.

The minimum consumable grades to be adopted arespecified in Tab 1 depending on the steel grade.

Consumable used for manual or semi-automatic weld-ing (covered electrodes, flux-cored and flux-coatedwires) of higher strength hull structural steels are to be atleast of hydrogen-controlled grade H15 (H). Where thecarbon equivalent Ceq is not more than 0,41% and thethickness is below 30 mm, any type of approved higherstrength consumable may be used at the discretion ofthe Society.

Especially, welding consumable with hydrogen-control-led grade H15 (H) and H10 (HH) shall be used for weld-ing hull steel forgings and castings of respectivelyordinary strength level and higher strength level.

Manual electrodes, wires and fluxes are to be stored in suit-able locations so as to ensuring their preservation in propercondition. Especially, where consumable with hydrogen-controlled grade are to be used, proper precautions are tobe taken to ensure that manufacturer’s instructions are fol-lowed to obtain (drying) and maintain (storage, maximumtime exposed, re-backing,...) hydrogen-controlled grade.

Table 1 : Minimum consumable grades

3.4.3 Welding procedures

Welding procedures adopted are to be approved by theSociety as defined in NR216 Materials and Welding, Ch 5,Sec 4.

The approval of the welding procedure is not required inthe case of manual metal arc welding with approved cov-ered electrodes, except in the case of one side welding onrefractory backing (ceramic).

3.4.4 Welder qualification and equipment

• Qualification of welders:

Welders for manual welding and for semi-automaticwelding processes are to be properly trained and are tobe certified by the Society according to the proceduresgiven in NR476 Approval Testing of Welders unless oth-erwise agreed.

The qualifications are to be appropriate to the specificapplications

Personnel manning automatic welding machines andequipment are to be competent and sufficiently trained.

The internal organization of the shipyard is to be such asto provide for assistance and inspection of welding per-sonnel, as necessary, by means of a suitable number ofcompetent supervisors.

Steel gradeButt welding, partial and full T penetration

weldingFillet welding

A 1

1B - D 2

E 3

AH32 - AH36DH32 - DH36

2Y2Y

EH32 - EH36 3Y

Note 1: Welding consumable approved for welding higherstrength steels (Y) may be used in lieu of those approved forwelding normal strength steels having the same or a lowergrade; welding consumable approved in grade Y having thesame or a lower grade.Note 2: In the case of welded connections between two hullstructural steels of different grades, as regards strength ornotch toughness, welding consumable appropriate to one orthe other steel are to be adopted.


NR 600, Ch 6, Sec 4

Non-destructive tests are to be carried out by qualifiedpersonnel, certified by recognized bodies in compliancewith appropriate standards.

• Equipment:

The welding equipment is to be appropriate to theadopted welding procedures, of adequate output powerand such as to provide for stability of the arc in the dif-ferent welding positions.

In particular, the welding equipment for special weldingprocedures is to be provided with adequate and dulycalibrated measuring instruments, enabling easy andaccurate reading, and adequate devices for easy regula-tion and regular feed.

3.4.5 Weather protection

Adequate protection from the weather is to be provided toparts being welded; in any event, such parts are to be dry.

In welding procedures using bare, cored or coated wireswith gas shielding, the welding is to be carried out inweather protected conditions, so as to ensure that the gasoutflow from the nozzle is not disturbed by winds anddraughts.

3.4.6 Butt connection edge preparation

The edge preparation is to be of the required geometry andcorrectly performed. In particular, if edge preparation is car-ried out by flame, it is to be free from cracks or other detri-mental notches.

3.4.7 Surface condition

The surfaces to be welded are to be free from rust, moistureand other substances, such as mill scale, slag caused byoxygen cutting, grease or paint, which may produce defectsin the welds.

Effective means of cleaning are to be adopted particularly inconnections with special welding procedures; flame ormechanical cleaning may be required.

The presence of a shop primer may be accepted, provided ithas been approved by the Society.

Shop primers are to be approved by the Society for a spe-cific type and thickness according to NR216 Materials andWelding, Ch 5, Sec 3.

3.4.8 Assembling and gap

The plates of the shell and strength deck are generally to bearranged with their length in the fore-aft direction. Possibleexceptions to the above will be considered by the Societyon a case-by-case basis.

The amount of welding to be performed on board is to belimited to a minimum and restricted to easily accessibleconnections.

The setting appliances and system to be used for positioningare to ensure adequate tightening adjustment and an appro-priate gap of the parts to be welded, while allowing maxi-mum freedom for shrinkage to prevent cracks or otherdefects due to excessive restraint.

The gap between the edges is to comply with the requiredtolerances or, when not specified, it is to be in accordancewith normal good practice.

Welds located too close to one another are to be avoided.The minimum distance between two adjacent welds is con-sidered on a case-by-case basis, taking into account thelevel of stresses acting on the connected elements.

3.4.9 Crossing of structural elementIn the case of T crossing of structural elements (one elementcontinuous, the other physically interrupted at the crossing)when it is essential to achieve structural continuity throughthe continuous element (continuity obtained by means ofthe welded connections at the crossing), particular care is tobe devoted to obtaining the correspondence of the inter-rupted elements on both sides of the continuous element.Suitable systems for checking such correspondence are tobe adopted.

3.4.10 Welding sequences and interpass cleaningWelding sequences and direction of welding are to bedetermined so as to minimize deformations and preventdefects in the welded connection.

All main connections are generally to be completed beforethe ship is afloat.

Departures from the above provision may be accepted bythe Society on a case-by-case basis, taking into account anydetailed information on the size and position of welds andthe stresses of the zones concerned, both during shiplaunching and with the ship afloat.

After each run, the slag is to be removed by means of achipping hammer and a metal brush; the same precaution isto be taken when an interrupted weld is resumed or twowelds are to be connected.

3.4.11 PreheatingSuitable preheating, to be maintained during welding, andslow cooling may be required by the Society on a case-by-case basis.

3.5 Inspection and check

3.5.1 GeneralMaterials, workmanship, structures and welded connec-tions are to be subjected, at the beginning of the work, dur-ing construction and after completion, to inspections by theShipyard suitable to check compliance with the applicablerequirements, approved plans and standards.

The manufacturer is to make available to the Surveyor a listof the manual welders and welding operators and theirrespective qualifications.

The manufacturer's internal organization is responsible forensuring that welders and operators are not employedunder improper conditions or beyond the limits of theirrespective qualifications and that welding procedures areadopted within the approved limits and under the appropri-ate operating conditions.

The manufacturer is responsible for ensuring that the oper-ating conditions, welding procedures and work scheduleare in accordance with the applicable requirements,approved plans and recognized good welding practice.


NR 600, Ch 6, Sec 4

3.5.2 Visual and non-destructive examinations

After completion of the welding operation and workshopinspection, the structure is to be presented to the Surveyorfor visual examination at a suitable stage of fabrication.

As far as possible, the results on non-destructive examina-tions are to be submitted.

Non-destructive examinations are to be carried out withappropriate methods and techniques suitable for the indi-vidual applications, to be agreed with the Surveyor on acase-by-case basis.

Radiographic examinations are to be carried out on thewelded connections of the hull in accordance with [3.5.3].The results are to be made available to the Society. The sur-veyor may require to witness some testing preparations.

The Society may allow radiographic examinations to bereplaced by ultrasonic examinations.

When the visual or non-destructive examinations reveal thepresence of unacceptable indications, the relevant connec-tion is to be repaired to sound metal for an extent andaccording to a procedure agreed with the Surveyor. Therepaired zone is then to be submitted to non-destructiveexamination, using a method deemed suitable by the Sur-veyor to verify that the repair is satisfactory.

Additional examinations may be required by the Surveyoron a case-by-case basis.

Ultrasonic and magnetic particle examinations may also berequired by the Surveyor in specific cases to verify the qual-ity of the base material.

3.5.3 Radiographic inspection

A radiographic inspection is to be carried out on the weldedbutts of shell plating, strength deck plating as well as ofmembers contributing to the longitudinal strength. Thisinspection may also be required for the joints of memberssubject to heavy stresses.

The present requirements constitute general rules: thenumber of radiographs may be increased where requested bythe Surveyor, mainly where visual inspection or radiographicsoundings have revealed major defects, specially for butts ofsheerstrake, stringer plate, bilge strake or keel plate.

Provisions alteration to these rules may be accepted by theSociety when justified by the organization of the shipyard orof the inspection department; the inspection is then to beequivalent to that deduced from the present requirements.

As far as automatic welding of the panels butt welds duringthe pre-manufacturing stage is concerned, the shipyard is tocarry out random non-destructive testing of the welds (radi-ographic or ultrasonic inspection) in order to ascertain theregularity and the constancy of the welding inspection.

In the midship area, radiographies are to be taken at thejoinings of panels.

Each radiography is situated in a butt joint at a cross-shapedwelding.

In a given ship cross-section bounded by the panels, a radi-ography is to be made of each butt of sheerstrake, stringer,bilge and keel plate; in addition, the following radiogra-phies are to be taken:

• bottom plating: two

• deck plating: two

• side shell plating: two each side.

For ships where B + C ≤ 15 m, only one radiography foreach of the above items is required.

This requirement remains applicable where panel butts areshifted or where some strakes are built independently fromthe panels. It is recommended to take most of these radiog-raphies at the intersections of butt and panel seams.

Still in the midship area, a radiographic inspection is to betaken, at random, of the following main members of thestructure:

• butts of continuous longitudinal bulkheads

• butts of longitudinal stiffeners, deck and bottom girderscontributing to the overall strength

• assembly joints of insert plates at the corners of theopenings.

Outwards the midship area, a programme of radiographicinspection at random is to be set up by the shipyard inagreement with the Surveyor for the major points. It is fur-ther recommended:

• to take a number of radiographies of the very thick partsand those comprising restrained joint, such as shaftbrackets, solid keel and its connection to bottom struc-ture, chain plates welding, stabilizer recesses, masts

• to take a complete set of radiographies or to increase thenumber of radiographies for the first joint of a series ofidentical joints. This recommendation is applicable notonly to the assembly joints of prefabricated memberscompleted on the slip, but also to joints completed inthe workshop to prepare such prefabricated members.

Where a radiography is rejected and where it is decided tocarry out a repair, the shipyard is to determine the length ofthe defective part, then a set of inspection radiographies ofthe repaired joint and of adjacent parts is to be taken.Where the repair has been decided by the inspection officeof the shipyard, the film showing the initial defect is to besubmitted to the Surveyor together with the film taken afterrepair of the joint.

3.5.4 Acceptance criteriaThe quality standard adopted by the shipyard is to be sub-mitted to the Society and applies to all constructions unlessotherwise specified on a case-by-case basis.

3.6 Modifications and repairs during con-struction

3.6.1 GeneralDeviations in the joint preparation and other specifiedrequirements, in excess of the permitted tolerances andfound during construction, are to be repaired as agreed withthe Society on a case-by-case basis.


NR 600, Ch 6, Sec 4

3.6.2 Gap and weld deformations

Welding by building up of gaps exceeding the required val-ues and repairs of weld deformations may be accepted bythe Society upon special examination.

3.6.3 Defects

Defects and imperfections on the materials and weldedconnections found during construction are to be evaluatedfor possible acceptance on the basis of the applicablerequirements of the Society.

Where the limits of acceptance are exceeded, the defectivematerial and welds are to be discarded or repaired, asdeemed appropriate by the Surveyor on a case-by-case basis.

When any serious or systematic defect is detected either inthe welded connections or in the base material, the manu-facturer is required to promptly inform the Surveyor andsubmit the repair proposal.

The Surveyor may require destructive or non-destructiveexaminations to be carried out for initial identification ofthe defects found and, in the event that repairs are under-taken, for verification of their satisfactory completion.

3.6.4 Repairs on structure already welded

In the case of repairs involving the replacement of materialalready welded on the hull, the procedures to be adoptedare to be agreed with the Society on a case-by-case basis.

4 Survey for unit production

4.1 General

4.1.1 The survey includes the following steps:

• survey at yard with regards to general requirements of [3]

• structure drawing examination (see [2])

• survey at yard during unit production with regards toapproved drawings, yard's response to comments madeby the Society during structure review examination andconstruction requirements.

These can only focus on the construction stage in progressduring the survey. It is to the responsibility of the inspectiondepartment of the yard to present to the Surveyor anydefects noted during the construction of the ship.

5 Alternative survey scheme for production in large series

5.1 General

5.1.1 Where the hull construction is made in large series,an alternative survey scheme may be agreed with the Soci-ety for hull to be surveyed as far as Classification is con-cerned or hull to be certified by the Society on voluntarybasis.

5.1.2 The general requirements for the alternative surveyscheme, BV Mode I, are given in the Society's Rule NoteNR320 as amended.

5.2 Type approval

5.2.1 GeneralThe type approval of a hull made of steel and built in largeseries comprises:

• examination, in accordance with the present Rule Noteof drawings and documents defining the main structuralcomponents of the hull

• examination of certain items of equipment and their fit-tings if requested by the Society Rules for the classifica-tion and/or certification of ships

• inspection of the first hull (or a hull representing thelarge series production).

5.2.2 Examination of drawingsThe structure drawing examination is to be carried out asdefined in [2].

5.2.3 Examination of certain items of equipmentThe equipment requiring a particular drawing examinationis defined in the present Rule. As a general rule, this equip-ment consists mainly in portholes, deck hatches and doors.

This examination may be carried out as defined in the Soci-ety’s Rules or through an homologation process, at the satis-faction of the Society.

5.2.4 InspectionsThe purpose of the inspections, carried out by a Surveyor ofthe Society on the initial hull of the series (or a representa-tive hull of the series), is to make surveys at yard during unitproduction with regards to approved drawings, yard'sresponse to comments made by the Society during structurereview examination and construction requirements as listedin [3].

5.2.5 Type Approval CertificateA Type Approval Certificate (TAC) is issued for the initialhull covered by the type approval procedure.

5.3 Quality system documentation

5.3.1 The quality system documentation submitted to theSociety is to include the information required in [3.1] and inthe Rule Note NR320 as amended.

5.4 Manufacturing, testing and inspection plan (MTI plan)

5.4.1 For each type of hull, the manufacturing, testing andinspection plan is to detail specifically:

• Materials:

Special requirements of the supplier (storage conditions,type of checks to be performed on incoming productsand properties to be tested by the yard before use).

• Storage conditions:

Information about storage sites (ventilation condi-tions to avoid condensation, supplier data sheetsspecifying the storage conditions, listing documentsto record arrival and departure dates for consign-ment).


NR 600, Ch 6, Sec 4

• Reception:Information about consignment (traceability of con-signment specifying date of arrival, type of inspec-tion, check on product packaging, types of specifictests performed).

• Traceability:Description of the yard process to ensure traceabilityof the materials from the time of the reception to theend of the production operations.

• Hull construction:Description of the yard process to ensure that the scant-lings and construction meet the rule requirements inrelation to the approved drawings.

• Installation of internal structure:Information about the main operations of the internalstructure installation.

• Equipment:The main equipment to be covered by the rules of theSociety are portholes, windows and deck hatches,watertight doors, independent tanks and rudders, the

scheduled tests and traceability on the equipment uponarrival and/or after installation.

• Testing and damage reference documents:

For all the previously defined MTI plan processes, pro-cedures are to be written, defining the types of tests orinspections performed, the acceptance criteria and themeans of handling non-conformities.

5.5 Society’s certificate

5.5.1 Certificate of recognition

After completion of the examination, by the Society, of thequality assurance manual, the MTI plan and the yard audit,a Certificate of recognition may be granted as per the provi-sions of NR320 Classification Scheme of Materials & Equip-ment, as amended.

5.5.2 Certificate of conformity

Each hull may be certified individually upon request madeto the Society.
