review of regulatory framework of - on the mos way · reference: msc1/circ. 1226 (2007): interim...

A. Papanikolaou, NTUA-SDL 1

Review of regulatory framework of Damage Stability of Dry Cargo and Passenger Ships

Two main categories of regulatory concepts and methodologies for the assessment of ship’s damage stability are nowadays in use, namely the deterministic and the probabilistic ones, leading to corresponding regulatory survivability standards (criteria). • Deterministic approaches to ship’s damage stability are based on prescriptive, semi-empirical rules and criteria derived from statistical analysis of historical damage data and practical experience. Because of the semi-empirical way of deriving the applied criteria, these methods cannot ensure a reliable minimum level of required survivability in case of new ship designs deviating from the past, nor is the attained level of ship safety known. • The probabilistic approach to damage stability relies on a rational statistical assessment of historical accidental data and combines this statistical information with semi-empirical criteria to more rationally assess

ship’s survivability by use of a probabilistic concept that takes into account a vast amount of possible damage scenarios with proper weight.

US, Nov 2015


Assessment methods of damaged stability of ships

•Deterministic Approach • Semi-empirical, prescriptive requirements, e.g. SOLAS74, SOLAS 90 • Performance-based (experimental or numerical simulation approaches), e.g. SOLAS 95 – Stockholm Agreement

• Probabilistic Approach • A.265, equivalent to SOLAS74 • Risk-based, …SOLAS 2009 • Goal-based, …new SOLAS 2016+…

US, Nov 2015


Deterministic vs. Probabilistic Approach to Ship Stability

The probabilistic assessment allows the determination of ship’s specific survivability (safety) level against capsize in case of flooding due to collision damages through her Attained Subdivision Index (probability of survival collision damages), whereas a deterministic damage stability standard does not correspond to a quantifiable safety level.

US, Nov 2015


Recent revisions of SOLAS damage stability regulations

(last 40 years) The regulatory requirements on ship’s damage stability differ depeding on ship type: - Passenger ships (SOLAS) - Dry cargo ships (SOLAS) - Liquid cargo ships (MARPOL) Main recent revisions of damage stability regulations for passenger and dry cargo ships.

1974

SOLAS

1974

1990

SOLAS 74

rev. 1990 SOLAS 74

rev. 1992 SOLAS 74 Rev. 1995

199 2 199 5

SOLAS

Part B - 1

Passenger Ships

Dry cargo ships

2009

SOLAS 74 Rev. 2009

SOLAS 74

Rev. 2009

US, Nov 2015


Passenger ships (deterministic SOLAS 90 requirements)

Main damage stability criteria of SOLAS 90 for passenger ships Examine for the maximum loading draft Intermediate Stages

GZ 0.05m, Range > 7o

θe < 15o

GZ

θ

GM 0.05m

A rea 0.015 m rad

Final Stage

Range 15 degrees

A ngle of inclination

7o 1CFL

12o 2CFL

GZmax GZreq

θrange = min (22o 1C FL, 27o 2CFL, θFLOODING, θ(GZ=0))

Intermediate Stages

GZ 0.05m, Range > 7o

θe < 15o

GZ

θ

GM 0.05m

A rea 0.015 m rad

Final Stage

Range 15 degrees

A ngle of inclination

7o 1CFL

12o 2CFL

GZmax GZreq

θrange = min (22o 1C FL, 27o 2CFL, θFLOODING, θ(GZ=0))

04.0

entHeelingMom

GZreq

Heeling moment: - Due to crowding - Launching of crafts of one side - Due to wind pressure

US, Nov 2015


RoPax – Ro-Ro passenger ships (deterministic-performance based)

Water On Deck

Stockholm Agreement-Resolution 14: for NW Europe (after the Estonia Accident)

EU Directive 2003/25/EC: for South Europe (after the SAMINA accident)

- In addition to the previously mentioned SOLAS 90 criteria, RoPax ships need to

fulfill the same criteria, assuming certain amount of WOD (Water On Deck,

namely their car deck)

-This hypothetical flood water mass is function of

- Damage freeboard

- Significant wave height in the area of operation

- Max flood water mass:

- 0.5m for 4.0m sign. wave height and 0.5m damage freeboard

US, Nov 2015


RoPax – Ro-Ro passenger ships (deterministic-performance based)

Water On Deck

-Calculatory method: formal compliance with the specified regulation

Alternatively (equivalent model test method, Res. 14),

- Model tests with model of damaged ship in side waves: equivalent

model test method, performance-based

-Generally: it proves in practice that the formal calculatory method is

by far more onerous (very conservative) with respect to ship’s survival

conditions. Thus, the equivalent model test method is mostly preferred

US, Nov 2015

Pres-4m-out.wmv


Deterministic or Probabilistic Approach?! Harmonization of existing & new damage stability

regulations

The harmonization of existing damage stability rules was decided by IMO and led to a unified assessment framework based on the probabilistic concept of estimating the damage stability of dry cargo and passenger ships.

The main goal of harmonization referred to the definition of survivability levels for dry cargo and passenger ships that are equivalent to those defined by the at that time in-force regulations for new-buildings.

The outcome of the harmonization process was SOLAS 2009!

Status at that time (years 2000-2003, project HARDER)

REFERENCE: MSC1/Circ. 1226 (2007): Interim explanatory notes to the SOLAS Chapter II-1 Subdivision and damage Stability Regulations

Basic ship type In force regulation Model

Dry cargo ships SOLAS B-1 Probabilistic

Passenger ships Resolution A.265 Probabilistic

Passenger ships SOLAS 90

(SOLAS 95)

Deterministic

US, Nov 2015


SOLAS 2009 – Damage stability

Calculation of the attained subdivision index Α

Pi-factor: Probability that only the compartment or group of compartments under consideration may be flooded. • Maximum damage length changed to 60 m in SOLAS 2009 (noting that it was 3%L + 3m, but not more than 11m in SOLAS 90!). • Damages of up to B/2 should be assumed (allowing penetration of longitudinal centre line bulkheads) REFERENCE: MSC1/Circ. 1226 (2007): Interim explanatory notes to the SOLAS Chapter II-1 Subdivision and damage Stability Regulations

tj

j

jjji svPA1

US, Nov 2015


Details of Probabilistic Model

Basic Approach

Probability that the ship will encounter

damage, P1

Probability of the resulting damage

location and extent, P2

Probability of the ship surviving the

damage, P3

Probabilistic Analysis of damage survivability


damage, P1




damage, P3



damage, P1




damage, P3



damage, P1




damage, P3


Collision/ Contact Grounding Ramming Fire/Explosion Other

Accidents

A, R

Indices

Deterministic Elements

in Probabilistic Rules

Collision/ Contact Grounding Ramming Fire/Explosion Other

Accidents

A, R

Indices

Deterministic Elements

in Probabilistic Rules Examination of probable damage scenarios

Loss of Watertight Integrity

A (710) vs. B (199) - 1.2 Damage length

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50

l/Lpp

f(x)

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

F(x

)

PDF-A

PDF-B

CDF-A

CDF-B

US, Nov 2015

A. Papanikolaou, NTUA-SDL

Risk Model (Event Tree) for collisions of cruise ships

11

Slow sinking: 72% Fatalities: 5%

Fast sinking: 18% Fatalities: 80%

27.0%

42.3077% Sinking (A-Index)

73.0%

Water ingress

4.0%

57.6923% 0.006%

37.5% Operational State

27.0%


73.0%

Water ingress

23.0%

57.6923% 0.0348%

27.0%


73.0%

Water ingress

73.0%

88.2353% 0.1688%

0.699% Initiator

62.5% 0.4369%

Collision

99.301% 99.301%

Ship type

No

Yes

Struck

En Route

Yes

No

No

Limited Waters

Yes

No

No

Terminal

Yes

No

No

Striking

Yes

Yes

Yes

US, Nov 2015


Probabilistic Model

The probability of survival of a ship after a damage (LOWI) due to collision with another ship of comparable size is expressed by the Attained Subdivision Index A. When calculating this index, a series of different damage scenarios for pre-determined loading conditions (full and partial load) are taken into account. The general form of the index A is the following:

wfi: weight functions for the various loading conditions (full, partial, light) Αi : attained subdivision index for each examined loading draft The attained subdivision index should not be less that the required index R, which is specified in the SOLAS regulations.

ii AwfA

Required Index R 1. Cargo ships, function of L 2. Passenger ships, function of L,

number of POB N and N1 (lifeboat capacity)

Summation of attained indices for various loading conditions: A = 0.4As + 0.4Ap + 0.2Al

32

11CNCL

CR

S

Dry Cargo Ships (L>100m): C1=128, C2=0, C3=152. Passenger Ships: C1=5000, C2=2.5, C3=15225.

US, Nov 2015


Modelling of survivability levels

The general formulation of new required survivability levels (project HARDER)

It should be noted, that due to the large scatter of the sample data of passenger ships, part of which were exhibiting unacceptably low attained indices, two alternative formulations for the R index were originally proposed by SLF47 for adoption by MSC 80. Alternative 1 corresponds to the best regression fitting of a reduced sample of ships with satisfactory levels of survivability, whereas Alternative 2 (finally adopted) considers an enhanced sample of passenger ships at worse regression fitting.

32

11CNCL

CR

S

Required Subdivision Index

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0 1000 2000 3000 4000 5000 6000

L + N

A,

R

A-f_heel_int

SLF47 Proposal,

Alt 2

C1=5000,

C2=2.5

C3=15225

SLF47 Proposal,

Alt 1

C1=2500, C2=3.5

C3=5413

Following a series of deliberations at IMO-SLF-MSC, IMO-MSC80 (2005), the finally adopted the following numerals for the Ci coefficients

Dry Cargo Ships (L>100m): C1=128, C2=0, C3=152. Passenger Ships: C1=5000, C2=2.5, C3=15225.

US, Nov 2015

A. Papanikolaou, NTUA-SDL

Comparison of Required Subdivision Indices

25

200005

230012

pobRIndex

000,6for97.0

000,1for9.0

1

pob

pob

RIndex

Pending final discussions/approval

by IMO

US, Nov 2015

review of regulatory framework of - on the mos way · reference: msc1/circ. 1226 (2007): interim...

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