managing temporary works - andrea robbins(hse)

Health and Safety Executive

Health and Safety Executive

Managing Temporary Works

Andrea RobbinsHM Inspector of Health and Safety

What are temporary works?

BS 5975:2008+A1:2011 defines temporary works as:

“those 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”

Temporary Works Examples -Earthworks

• Piling Platforms, Underpinning and Cofferdams etc.

Construction of a Piling PlatformCompleted Piling Platform Underpinning

Temporary Works Examples

• Earthworks – (Supports) for Trenches, Excavations

Trench Boxes

Close Boarded Trench Support

Design of trench box -access ladder and

edge protectionattached to box

Waler Frames –For Medium Sized Trenches

Hydraulic / Mechanical StrutsStrutting Frame


• Structures – Formwork & Falsework

Formwork (Shuttering) Falsework (Supports)


• Structures – Scaffold, Propping & Façade Retention

Façade Retention

Propping


• Structures – Edge Protection, Loading Bays, Temporary Bridges, Hoarding, and Signage etc

Edge ProtectionSignage

Hoarding

Temporary Bridges

Loading Bays

Signage On Scaffolds etc


• Plant - Mobile Crane Outrigger Design, Hoists / Mast Climbers, Tower Crane Bases etc.

Mobile Crane Outrigger Design

Tower CraneBase

Hoists / Mast Climbers

Legal obligations – CDM Regulations 2007

• Reg 4 – competence required of all those with a role to discharge in planning, design and execution of TW;

• Regs 5 & 6 - co-operation and co-ordination of activities, including TW, incumbent on all involved;

• Reg 10 – client’s duty to provide pre-construction information, e.g. • Reg 10 – client’s duty to provide pre-construction information, e.g. ground conditions, structural drawings;

• Reg 11 – duties of designers: avoidance of foreseeable risk arising from preparing or modifying designs;

• Reg 18 – additional duties of designers: provision of information to assist the CDM Co-ordinator;

• Regs 13 & 22 – duties of contractors and the principal contractor: planning, management and monitoring of construction work;

Legal obligations – CDM Regulations 2007

• Reg 20 – duties of CDM(Cs) – all reasonable steps to ensure designers comply with their duties and to ensure co-operation between designers and principal contractors in relation to any design or design change;

• Reg 26 – safe place of work – scaffolding, flooring, stairs etc;etc;

• Reg 28 – stability of structures: any support or temporary structure must be designed, installed and maintained so as to withstand foreseeable loads;

• Reg 29 – demolition or dismantling: planning and recording of arrangements;

• Reg 31 – excavations: planning and execution;• Reg 32 – cofferdams and caissons: design, planning and

execution;

Temporary Works Procedure

• Appointment of a Temporary Works Co-ordinator (TWC)• Completion and maintenance of a Temporary Works Register• Preparation of design briefs for elements identified in the register• Production of temporary works designs• Temporary works design check•• Preparation of risk assessments/method statements• Pre-erection inspection of the TW materials and components• Supervision of erection of temporary works• Check that the TW have been erected in accordance with the design• Issue a formal “permit to load” where necessary• Confirm that the TW have attained adequate strength to allow TW to

be dismantled • Issue a formal “permit to dismantle” where necessary

Temporary Works Co -ordinator

• Formal appointment in writing

• Must be competent = experience + a formal qualification, e.g.

[1] Degree/HND qualified as a minimum

[2] Chartered Civil/Structural Engineer

[3] Has completed formal temporary works training

Temporary Works Co -ordinator

Typical duties:• To determine the TW for a project, compile a TW register

and keep all TW records;

• To ensure the procedures for the control of TW are implemented on site; implemented on site;

• To determine the type and risk class of TW on a project;

• To ensure that all TW are designed and checked appropriately;

• To issue the permit to load and permit to dismantle; and

• To ensure that all TW activities are adequately planned and supervised.

Temporary Works Supervisor

• Assists the TW Co-ordinator

• Carries out checks on the implementation process of the TW.

•• May issue the permit to load and permit to dismantle when specifically authorised for a defined scope and range of work.

CDM Co-ordinator

• Ensures co-operation between permanent and temporary design;

• Check suitability of construction phase plan – stability of structures – have they plan – stability of structures – have they been addressed;

• Advises client of the suitability of the construction phase plan.

Temporary works register

Should include:

• Design brief number;

• Short description of temporary works;

• Date required for design solution;• Date required for design solution;

• Risk category of temporary works;

• Designer and design checker;

• Date design complete;

• Date design checked/approved; and

• Erection complete and checked or “permit to load” then “permit to dismantle”.

Risk classes of temporary works

High risk (class 1 or class A)• Falsework and formwork over 3m high• Hoarding and fencing over 3m high• Façade retention schemes• Complex designed scaffold• Complex designed scaffold• Complex propping schemes – multiple props and multiple levels• Needling of structures greater than 2 storeys high• Working platforms for cranes and piling rigs; tower crane bases• Ground support schemes greater than 3m deep • Trenchless construction including headings, thrust bores, mini

tunnels• Cofferdams• Complex structural steelwork and pre-cast concrete erection

schemes


Medium risk (class 2 or class B)

• Hoardings & fencing up to 3m high

• Simple designed scaffolds

• Falsework up to 3m high

•• Formwork for concrete columns and walls up to 3m high

• More complex propping schemes – multiple props at single level

• Needling of structures up to 2 storeys high

• Foundation underpinning not using piles

• Excavations up to 3m deep in good ground

• Safety net systems fixed to robust primary members

• Temporary roofs


Low risk (class 3 or class C)

• Internal hoarding systems and temporary partitions not subject to wind or differential air pressure or crowd loading

• Fencing and hoarding up to 1.2m high

• Standard scaffold• Standard scaffold

• Formwork less than 1.2m high

• Shallow excavations less than 1.2m deep in good ground

• Simple propping schemes – 1 or 2 props

• Small MEWPs operating on a pavement designed for HGV’s or on internal ground bearing slabs and working within the level of tolerances set by the manufacturer

Temporary works design brief

• Purpose of TW – include drawings of permanent works and any specifications;

• Required dimensions and any known constraints;constraints;

• Particular loads including impact loads;

• Ground conditions – i.e. soils, groundwater etc;

• Site conditions including services, adjacent structures and access;

• Available materials and equipment; and

• Construction sequence and loading stages.

Categories of Design ChecksTable 1 BS5975:2008+A1:2011

Category Scope Comment Independence of checker

0 Restricted to standard solutions only, to ensure the site conditions do not conflict with the scope or limitations of the chosen standard solution.

This applies to the use of standard solutions and Not the original design, which will require both structural calculation and checking to category 1, 2 or 3 as appropriate.

Because this is a site issue, the check may be carried out by another member of site or design team.

1 For simple designs. These may include: formwork: false work (where top restraint is not assumed): needling and propping to brickwork openings in single storey construction.

Such designs would be undertaken using simple methods of analysis and be in accordance with the relevant standards, supplier’s technical literature or other reference publications.

The check may be carried out by another member of the design team.

2 On more complex or involved designs. Designs for excavations, for foundations, for structural steelwork connections, for reinforced concrete.

Category 2 checks would include designs where a considerable degree of interpretation of loading or soils’ information is required before the design of the foundations or excavation support or slope

The check should be carried out by an individual not involved in the design and not consulted by the designer.

3 For complex or innovative designs, which result in complex sequences of moving and/or construction of either the temporary works or permanent works.

These designs include unusual designs or where significant departures from standards, novel methods of analysis or considerable exercise of engineering judgement are involved.

The check should be carried out by another organization.

Temporary works design checks

• For high risk TW there must be an independent check made on the design.

• For medium risk TW the check can be undertaken by the same organisation as undertaken by the same organisation as long as there is documentary proof of the independence of the checkers.

• For low risk TW the checks can be undertaken by someone in the site team or the design team.

Temporary works design checks

In all cases the design check should provide an independent check on:

1) Design concept;

2) Strength and structural adequacy (including lateral stability and overturning etc); and

3) Compliance with the design brief.

Why are temporary works important?

GOOD temporary works can bring:

• Better safety;

• Enhanced efficiency, quality, productivity; • Enhanced efficiency, quality, productivity; and

• More certainty on completion times and cost.

What happens when TW go wrong?Causes:

• No (or inadequate) TW procedure

• No (or inadequate) TWC appointed

• Lack of competent contractor/developer/ builder

• No (or inadequate) TW design• No (or inadequate) TW design

• Inadequate design brief or failure to carry out proper investigation of ground conditions, underground services or structural condition of existing buildings

• Unauthorised changes to an approved TW design

• Lack of competent TW designer and/or erectors

What happens when TW go wrong?Causes:

• Incorrect estimation of loads to be supported (overloading)

• Lack of adequate lateral stability: inadequate horizontal and/or diagonal bracing to resist horizontal and/or diagonal bracing to resist lateral (wind) loads

• Inadequate foundations

• No temporary works equipment available

• Inappropriate use of TW equipment or other non TW equipment being used for the purpose of TW

• TW poorly constructed

What happens when TW go wrong?Consequences:

• Collapse or failure of the TW;

• Structural failure and/or collapse of the permanent works;

• Uncontrolled ingress or egress of materials, • Uncontrolled ingress or egress of materials, spoils or water;

• Collapse of adjacent structures;

• Risk of fatalities and injuries to workers and members of the public;

• Delays and increased costs; and

• Financial & commercial risks to contractors, sub-contractors, designers, suppliers & clients.

Basement construction, London E17

When it goes wrong

• Was the contractor competent ?

• Was the initial • Was the initial construction phase plan suitable?

CASE STUDIES

AA Fanum House, CardiffScaffold collapse, 13 December 2000

White Hart Lane, London

Shanghai June 2009

What is HSE doing?

Work Plan 2011/12 – Aims for Temporary Works

• Promote awareness & knowledge of the importance of managing TW effectively;of managing TW effectively;

• Improve contractors’ management arrangements for TW;

• Increase the competence of those involved in TW management & design; and

• Reduce accidents arising from TW failures

What is HSE doing?

How will this be achieved?

• HSE Construction inspectors to target TW activities during routine site inspections;

•• A programme of targeted visits by HSE Civil/Structural Engineers

• Initial engagement with principal contractors

• May involve some “tracking back” from site to the CDM-C and the TW designer

Sources of information

• HSE website - http://www.hse.gov.uk

• SIM 02/2010/04 – The Management of • SIM 02/2010/04 – The Management of Temporary Works in Construction

• BS5975:2008+A1:2011 – Code of practice for temporary works procedures and the permissible stress design of falsework

Any questions?

managing temporary works - andrea robbins(hse)

Documents

temporary works registershould

temporary works supervisor

permanent works

design issue

formal temporary workstraining

tw coordinator

design change reg

tw activities