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Temporary Works on Construction Sites

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Fundamental Necessity

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Temporary Works: Examples

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Temporary Works: Examples

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Temporary Works: Examples

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Temporary Works: Examples

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Temporary Works: Examples

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8

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Loddon Viaduct Collapse

• Loddon Viaduct Collapse, Reading, 3 people killed

• One of the factors leading to the Bragg Report

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Key Conclusions of Bragg Report 1975Parliamentary Enquiry

• A lack of clarity in the division of responsibility.

• The need for a ‘falsework co-ordinator’.

• A failure to reflect the ‘high risk’ nature of falsework in the design and site controls.

• The essential need to provide robust means of ensuring lateral stability, and specifically so

at forkhead level.

• The need to discard damaged or distorted items.

• The need for stiffeners at all substantive load bearing points in steel grillages

• Falsework requires the same skill and attention to detail as the design of permanent structures of like complexity, and indeed falsework should always be regarded as a structure in its own right, the stability of which at all stages of construction is paramount for safety.

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Bragg Report

Main recommendations for Falsework:

• Design based on a site design brief

• Design checked by a fully qualified engineer

• Permanent works designer to have the opportunity to comment

• Training, Codes, Regulations

• Appoint a Temporary Works Co-Ordinator

Recommendations Incorporated into BS5975 in 1982

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Legal Hierarchy: Temporary Works

HSAWA

WAH

BS5975

MHSW

LOLER

PUWER

CDM

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Overview

• General duties

• HASWA74, MHSWR99

• Inspections

• Covered by virtually all regulations to ensure that structures, equipment and the environment

remain in a safe condition and people work in a safe manner

• Stability – above and below ground

• Risk assessment, procedures, inspections, CDM Part 4

• Design (scaffold)

• WAH Regulations, CDM roles, TG20:13

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CDM Regulations

Part 4 General Requirements

• Regulation 19 Stability of structures

• Regulation 20 Demolition or dismantling

• Regulation 22 Excavations

• Regulation 23 Cofferdams and caissons.

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BS5975Code of Practice for temporary works procedures and the

permissible stress design of falsework

Obligatory not legislative

• Legal requirement for safe systems of work, through suitable management arrangements

• HSE guidance:

…Contractors should be able to demonstrate that they have in place effective arrangements for controlling risks arising from the use of temporary works. These are usually captured in a temporary works procedure……

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Definition: BS5975 - Temporary Works

• ‘parts of the works that allow or enable construction of, protect, support or provide

access to, the permanent works and which might or might not remain in place at

the completion of the works’

• An engineered solution

• used to support or protect either an existing structure or the permanent works during

construction,

• or to support an item of plant or equipment,

• or the vertical sides or side-slopes of an excavation during construction operation on site

• or to provide access.

• May be removed or left in place after the completion of the permanent works but in

the latter case would not necessarily contribute to the strength of the permanent

works.

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HSE Guidance

‘include but are not limited to’:

• Earthworks - trenches, excavations, temporary slopes and stockpiles.

• Structures – formwork, falsework, propping, faҫade retention, needling, shoring,

edge protection, scaffolding, temporary bridges, site hoarding and signage, site

fencing, cofferdams.

• Equipment/plant foundations – tower crane bases, supports anchors and ties for

construction hoists and mast climbing work platforms, ground works to provide

suitable locations for plant erection (e.g. mobile cranes and piling rigs)

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Permanent Works

• The structures and arrangements the client needs on completion of the works

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Temporary Versus Permanent

Element Permanent works Temporary works

Robustness High Often low

Duration of use 60 – 120 years Days, weeks or months

Component types Bespoke to project,

always new

Suppliers’ systems, often second

hand, grouped, eccentricity

Planning Widely negotiated, can

take years

Quick, under site pressure

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Risks Associated with Temporary Works

• Risk of single/multiple fatalities and serious injuries to workers and public

• Collapse or failure of the Temporary Works

• Structural failures and collapse of the Permanent Works

• Uncontrolled ingress or egress of materials, spoil and water

• Collapse of adjacent structures

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HSE Guidance

Inadequate temporary works

Poor design, construction or overloading of

temporary works

Collapse or failure of temporary works

Falls from height

Collapse of permanent structure

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Key Procedures

• Appointments

• Competence

• Designs

• Checks and certified designs

• Inspection during and after erection

• Inspection during works

• Permits

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General Flow Diagram

TWC

‘Adequate’ brief

Design Check

Information to site team

Changes to:

• site condition

• design

• materials

Permit to load

Permit to unload

Use and maintenance

Build

Register (schedule)

Assess risk - is a design needed?

Yes

TWS

Defines and records

responsibilitiesPossible input:

• Client

• Main contractor

• Site team

• Design consultants

• Timescale

• Site investigations

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Key Roles

• Designated Individual (DI)

• Temporary Works Coordinator (TWC) – Principal Contractor’s and Others

• Temporary Works Supervisor (TWS).

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Temporary Works Coordinator

• Named person responsible for the safe and timely management of the TW on site

• Only on TWC’s authority are TW loaded or unloaded

• Project Manager has responsibility to manage erection of TW so the TWC is

technically independent and separate from pressures of production

• TWC should define and record duties of each TWS

‘For a given site, the main or principal contractor should appoint a temporary works coordinator who is

responsible for the implementation of their organisation’s temporary works procedures and those of all other

contractors who are directly or indirectly in their employ.’

• Competent with relevant training

• Managers interface between organisations and has an overview of the whole project

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Temporary Works Procedure

Establishing responsibility for:

• Appointment of TWC and TWS

• States limits of authority of TWS

• Specifies the management of the design process

• Who writes the brief

• Production of an independently checked and certificated design

• Procurement of materials

• Control of erection, safe use and maintenance and dismantling

• Checking of erected TW and control of use, maintenance and dismantling to ensure compliance

with design

• Procedure for issuing permits to load/dismantle

Formal letters of appointment required for the 3 roles. Procedure could contain the standard letters with

signed copies retained by the DI.

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Liverpool Crane Collapse 2009

• Crane fell into partially completed apartment

block

• Driver paralysed from waist down

• Inadequate foundations was determined as

the cause

• First crane foundation designed by Engineer

• No TW procedure or TWC

• Pile rebar clashed with crane ‘grillage’

foundation so was cut

• New bars dowelled in - some not deep

enough, some not fixed in.

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Key Documents

• Appointments

• Register

• Design brief

• Inspection templates

• Design drawings, schedules, limitations

• Check certificate

• Permits

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Avoiding Failure

• People: (Corporate and Individual)

• Process:

• Clarity of responsibility

• Procurement

• Site wide issues and planning ahead

• Design and checks

• General

• Installation

• Use, maintenance and dismantling

• Product

• Standard solutions, condition and sourcing

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People

• Training and Competence• Roles

• Product

• Process

• Supervision• Adequate

• Lines of communication

• Corporate Competence• Management leading by example and enforcing rules

• Policies and procedures in place

• Good monitoring processes set and implemented

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Process

Suitable and sufficient Temporary Works procedures

• Interfaces identified• Clarity of responsibility

• Good practice identified• Identifying site-wide issues and planning ahead

• All key points identified• Process clear and unambiguous

• Logical, sequential, audited

• Design briefs and designs are fit for purpose

• Method statements are written and followed

• Permits to use are signed off by a competent person

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Product

Products used are suitable and in a good condition.

• What are the ‘standard solutions’

• Is product information provided / available

• Quality supplier

• Are substitutions checked with the designer

• Are materials in good condition and regularly inspected

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Categories of Risk

• Simple, low risk (Category 0 – 1)

• Standard scaffolding

• Formwork and hoarding < 1.2m high

• Simple prop schemes

• Shallow excavations <1.2m deep.

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Categories of Risk

• More complex / medium risk (Category 2)

• Falsework to 3m high

• Formwork to 3m high

• More complex propping schemes – multiple at single level

• Excavations to 3m deep

• Hoarding to 3m high

• Simple designed scaffold

• Temporary roofs.

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Categories of Risk

• Complex / potentially high risk (Category 3)

• Falsework / formwork over 3m high

• Working platforms for cranes and piling rigs

• Complex propping schemes – multiple on multiple levels

• Excavations / ground support greater than 3m deep

• Hoarding over 3m high

• Complex designed scaffold

• Complex steelwork

• Cofferdams

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Categories of Risk

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Questions