tunnel form document

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Dunne Group LtdTunnel Form2009

1

INTRODUCTION

Dunne Building & Civil Engineering Limited operates

within the United Kingdom to fulfil the requirements of

Management and Construction Management Forms of

Contract. It has developed its operational and

management systems to become recognised as a

leading specialist reinforced concrete frame Trade or

Package Contractor. Whilst its core business remains

in the Reinforced Concrete Civils and Structural

market, the Company has expanded its scope of

operations to include other specialist package works

such as Blockwork, Plant Hire and Pre-cast Concrete

and is now actively involved in General Building and

Main Contract works. The flexibility demonstrated by

this successful broadening of its market base has

enabled the Company to maintain its financial strength

in a diminishing and increasingly competitive industry.

The Group’s wholly owned subsidiary, Dunne Plant

Hire Limited also operates from this base, providing a

full plant service to our Construction Projects, including

excavation and earthmoving equipment, mobile

concrete pumps and modular falseworks and

shuttering systems.

Our policy of continued investment in new plant and

construction techniques, together with the proper

management and maintenance of this plant holding, is

essential in providing our clients with a cost effective

product of high quality, whilst not prejudicing our high

safety standards.

Dunne Building & Civil Engineering Limited offers to the

Client and his Professional and Management Team the

experience and expertise to provide the professional,

non-contractual and proactive approach, which will be

essential to the success of this Project.




2

TUNNEL FORM CELLULAR STRUCTURES

GENERAL

Tunnel form is a formwork system that allows

construction of cellular walls and slabs in one

operation on a daily cycle. It combines the speed,

quality and accuracy of offsite production with the

flexibility and economy of in-situ construction and is

recognised as a modern method of construction.

The result is a cellular reinforced concrete structure,

the surfaces of which are of sufficiently high quality to

require only minimal finishing for direct decoration.

The system creates an efficient load bearing structure

for use in a wide variety of applications. It is

particularly effective in projects suited to repetitive

cellular construction such as residential blocks, hotels,

student accommodation, barracks and prisons.

Tunnel form is becoming one of the most common

methods of cellular construction as its cost

effectiveness, productivity and quality benefits are

being realised on a wide range of projects throughout

the UK.

Tunnel form is a fast-track method of construction that

is well suited to repetitive cellular projects such as

hotels, social housing and student accommodation.

Recognised as being a modern method of

construction, tunnel form simplifies the whole

construction process by enabling a smooth and fast

operation that can result in frame costs being reduced

by up to 15 percent and provide frame programme

time savings of up to 25 percent.




3

THE 24 HOUR SITE CYCLE

3. LATEMORNINGTunnels arealigned and

reinforcementfixed

5. OVERNIGHT

ThermalCuring

1. STARTConcrete Test toensure previousday’s pour hasreached striking

strength

4. AFTERNOONPreparations

completed andConcrete poured

2. EARLYMORNINGTunnels are

Struck, Cleanedand craned into

next cell

24HOURSITE CYCLE

During the tunnel form construction process, a structural tunnel is created by pouring concrete

into steel formwork to make the floors and walls in one monolithic process. Each 24 hours, the

formwork is moved so that another tunnel can be formed. When a storey has been completed,

the process is repeated on the next floor. A strong, monolithic structure is thus constructed that

can reach 40 or more storeys in height.




4

THE 24 HOUR SITE CYCLE IN PICTURES

1. Start – Concrete Test to ensure previous day’s pour has reached striking strength. The

use of high strength concrete ensures fast construction, typically 15N/mm2 at 14 hours.

2. Early Morning – Tunnels are struck, cleaned and craned into the next cell

3. Late Morning – Tunnels are aligned and reinforcement fixed

4. Afternoon – Preparations completed and concrete poured

5. Overnight – Thermal curing




5

TUNNEL CELL DESIGN

Tunnel form creates cells which are 2.4 to 6.6m

wide. The larger cells can be subdivided to create

smaller rooms. Where longer spans are required

up to 11m, the tunnel form can be extended using a

mid span section infill.

Walls can be designed as deep beams and

supported at low level on finished columns to

accommodate under croft car parking.

With tunnel form, the Structural Engineer designs

the one way spanning slabs and walls in

accordance with BS 8100. The innovation is with

the formwork system. Similarly, the Architect must

accept to work with the constraints of regular wall

alignments for tunnel form to be a structural

solution.

The techniques used for tunnel form are already

familiar to Dunne Building and Civil Engineering

Ltd. On average, a team of eight plus a crane driver

can strike and fix 300m2 of formwork each day,

including placing 35m3 of ready mix concrete

(typically 2.5 cells).

The technique provides further inherent benefits of

concrete: high levels of thermal mass, sound

insulation and fire resistance.




6

SERVICE RUNS

Service runs can be pre-installed before the concrete is poured

Other facilities such as bathroom pods can be installed as completed units using existing

access platforms

FINISHING

The smooth face of the steel formwork results in

a high quality finish that can be decorated

directly. This reduces the need for finishing

trades thereby providing additional cost savings

and speeding the entire process.

Tunnel form provides a winning combination of

the speed, quality and accuracy of factory

production with the flexibility and economy of in-

situ construction.




7

PERCEPTION OF BENEFITS

Flexibility in Design

The large bays constructed using tunnel form, provide exceptional flexibility in the design and

layout of the building and allow a high degree of freedom in the final appearance. The

elevations can be adapted by using extendable formwork to create cantilevered balconies

and the exterior can be finished in any way the architect requires, from brick slips on highly

insulated framed infill panels, to sophisticated curtain walling systems.




8

The high levels of dimensional accuracy achieved with tunnel form and the superior load

distribution result in a strong, solid monolithic structure suitable for a multitude of uses. The

ability to create clear spans up to 11m wide provides the opportunity to use non load-bearing

internal partitions that can be moved to provide alternative layouts.

Fast and Economical to Construct

Value engineering starts with the early involvement of the Contractor. In comparison with

traditional R.C. Structures, a general 20 to 25 percent reduction in programme and 10 to 15percent reduction in cost may be realised. The resulting monolithic construction can also

produce savings in the foundations.

Quality

Quality is enhanced despite the speed of construction. The precise, even steel face of the

formwork creates a smooth, high quality finish capable of receiving direct decoration with the

minimum of preparation (a skim coat may be required). This reduces the requirement for

finishing trades, thus providing additional cost savings and speeding the entire process.




9

Productivity and Control

The formwork is specially adapted for each project.

The repetitive nature of the system and the use of

prefabricated forms and reinforcing mats/cages

simplifies the whole construction process, producing

a smooth and fast operation. The techniques used

are already familiar to the industry, but with tunnel

form construction there is less reliance on skilled

labour. On average, a team of eight site operatives

plus a crane driver can strike and fix 300m

2

offormwork each day, including placing approximately

35m3 of ready-mixed concrete. The work can

continue in all weather except high winds, and

heaters can be used to accelerate the concrete

curing process.

The schedule provided by the 24-hour cycle means

each operative knows exactly what to do and when,and works to a precisely detailed plan. The smaller

work teams and predictable, measurable daily

production rates simplify and enhance overall

control of the project. Known completion times

make scheduling of material deliveries and follow-on

trades more accurate and optimise cash flow by

facilitating ‘just in time’ principles. By quickly

providing protection, the system allows the follow up

trades to commence work on completed rooms

while work proceeds on upper floors.




10

Health and Safety

Tunnel form has integral working platforms and edge protection systems. In addition, the

repetitive, predictable nature of the tasks involved encourages familiarity with operations and

productivity improves as construction progresses. The minimal requirement for tools and

equipment when moving tunnel forms further reduces the risks of accidents on site.

Comprehensive Method Statements and full safety risk assessments enhance safety in tunnel

form’s application. The system meets all current Health and Safety construction site

requirements and for the Client and End User, the superior fire resistance and strength

inherent in the concrete structure increases confidence in the building itself.




11

Environment

In today’s environmentally conscious society, we are under ever-increasing pressure to reduce

waste and provide energy efficient buildings within sustainable communities. Tunnel form

provides benefits in key areas:

The in-situ casting of units on site and the local availability of ready-mixed concrete

supplies reduce transportation impacts.

Just-in-time deliveries and near zero wastage produce an overall tidier site withassociated cost savings and safety benefits plus minimum disruption where the site is

already partly occupied.

Concrete’s thermal mass coupled with correct insulation and boiler design minimises

heating costs and can even reduce air-conditioning requirements, with the resultant

benefits for the environment. The monolithic and accurate structure facilitates airtight

construction – an expected requirement in the 2005 amendment to the Building

Regulations, Part L.

Direct finishes and durable walls minimise decoration, repair and refurbishment costs.

Wallpaper can be directly applied or a skim coat may be used to provide a perfect

plastered finish.

In combination with the correct flooring and ceiling systems for separating floors, tunnel

form floors can use the Part E Robust Detail No. E-FC-2 and be confident of passing

the pre-completion testing (PCT) required for Part E sound insulation. With tunnel

form, party walls are simple and can be made of the concrete itself or be non load-

bearing demountable partitions of lightweight concrete block work, or plasterboard

systems. All of these require PCT with a range of suggested options in the Part E

document or from the acoustic specialist, which should satisfy the new requirements.




12

Ease of service installation

Service runs can be pre-installed before the concrete is poured. Other facilities such

as bathroom pods can be installed as completed units using existing access

platforms.

Modern Methods of Construction (MMC)

The use of tunnel forms brings factory quality and efficiency to site and so is

recognised as a Modern Method of Construction under the initiative being promoted

by the ODPM. Referenced in Housing Corporation documentation, it is eligible for

use by Housing Associations as a MMC System.

Support

The tunnel form suppliers/contractors provide full design and technical support to

ensure engineers, architects and site staff are all familiar with the system and its

application as the project starts, enabling time and cost savings to be achieved. If the

site staff is inexperienced with tunnel form construction, the supplier’s site training

quickly brings them up to speed.




13

Acoustic Test Report

The new tunnel form block of student accommodation at the University of East Anglia was

acoustically tested in August 2004 with excellent results.

Although non domestic residences, university halls, hotels and hostels all have to

comply with the new Building Regulations’ sound requirements of Part E 2003, they will

not be permitted to use the Robust Detail Route and will have to undergo pre-

completion testing (PCT). As a monolithic structure, tunnel form is one of the few

systems that should be totally repeatable and therefore can be used with confidence onfuture projects using the same construction details.

Two separating floors in the new block, consisting of 250mm of concrete with a stuck-

down carpet and no ceiling finish beneath, were tested. They both exceeded the

regulations by more than 5 dB for both airborne and impact sound insulation (actually

meeting the levels required by Robust Details). Had a floating floor and suspended

ceiling been incorporated the results would have been even better.

Two separating walls were also tested, each comprising 180mm concrete with a 2mm

plaster skim finish. Both met the PCT requirement and could have exceeded it further

with the addition of wall linings.

This test, no 040901, carried out by an independent acoustic expert, is downloadable from the

Residential section of The Concrete Centre website at www.concretecentre.com



Dunne Group Ltd Head Office

Dunne Group Ltd

Head Office: Inchmuir Road, Whitehill Industrial EstateBathgate EH48 2EW

Tel: 01506 657777 Fax: 01506 657770

Regional Office: 4205 Park Approach, Thorpe Park,Leeds LS15 8GB

Tel: 01132 840540 Fax: 01132 840541

Email: [email protected]

Web: www.dunne-group.com

Regional Office: Leigh Commerce Park, Greenfold Way,Leigh, Greater Manchester WN7 3XHTel: 01942 267470 Fax: 01942 267471

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