Temporary Works by definition - “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”.
Health and Safety Health and SafetyExecutive Executive Managing Temporary Works Andrea Robbins HM 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 Platform Completed Piling Platform Underpinning
Temporary Works Examples• Earthworks – (Supports) for Trenches, Excavations Waler Frames – For Medium Sized Trenches Close Boarded Trench Support Design of trench box - access ladder and edge protection Trench Boxes attached to box Hydraulic / Mechanical Struts Strutting Frame
Temporary Works Examples• Structures – Edge Protection, Loading Bays, Temporary Bridges, Hoarding, and Signage etc Signage Edge Protection Temporary Bridges Hoarding Signage On Scaffolds etc Loading Bays
Temporary Works Examples• Plant - Mobile Crane Outrigger Design, Hoists / Mast Climbers, Tower Crane Bases etc. Hoists / Mast Climbers Tower Crane Base Mobile Crane Outrigger Design
Legal obligations – CDM Regulations2007• 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. 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 Regulations2007• 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;• 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.  Degree/HND qualified as a minimum  Chartered Civil/Structural Engineer  Has completed formal temporary works training
Temporary Works Co-ordinatorTypical 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;• 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 been addressed;• Advises client of the suitability of the construction phase plan.
Temporary works registerShould include:• Design brief number;• Short description of temporary works;• 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 worksHigh 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 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
Risk classes of temporary worksMedium 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
Risk classes of temporary worksLow 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• 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;• 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+A1:2011Category Scope Comment Independence of checker Restricted to standard solutions only, This applies to the use of standard Because this is a site issue, the 0 to ensure the site conditions do not conflict with the scope or limitations of solutions and Not the original design, which will require both check may be carried out by another member of site or design the chosen standard solution. structural calculation and checking team. to category 1, 2 or 3 as appropriate. For simple designs. These may Such designs would be The check may be carried out by 1 include: formwork: false work (where top restraint is not assumed): needling undertaken using simple methods of analysis and be in accordance another member of the design team. and propping to brickwork openings in with the relevant standards, single storey construction. supplier’s technical literature or other reference publications. On more complex or involved designs. Category 2 checks would include The check should be carried out 2 Designs for excavations, for foundations, for structural steelwork designs where a considerable degree of interpretation of loading by an individual not involved in the design and not consulted by the connections, for reinforced concrete. or soils’ information is required designer. before the design of the foundations or excavation support or slope For complex or innovative designs, These designs include unusual The check should be carried out 3 which result in complex sequences of moving and/or construction of either designs or where significant departures from standards, novel by another organization. the temporary works or permanent methods of analysis or works. considerable exercise of engineering judgement are involved.
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 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 checksIn 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; 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 • 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 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, 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.
What is HSE doing?Work Plan 2011/12 – Aims for Temporary Works• Promote awareness & knowledge of the importance 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 Temporary Works in Construction• BS5975:2008+A1:2011 – Code of practice for temporary works procedures and the permissible stress design of falsework