The Institution of Structural Engineers launched its second version of its Guidance Document for Temporary Demountable Structures on 27th May at its Headquarters in London. This document is for the use of Clients, Contractors, Engineers, and Local Authority Enforcers. The "Guide to Safety refers it to at Sports Grounds" refers to this document. It is also anticipated that the new version of the "Pop Concert" Code will rely on the document for technical aspects.
The first version of this document caused uproar by the events Industry. In response to this The Department of the Environment set up a "Monitoring Group" with representatives from all sides of the Industry. The writer represented the Institute of Building Control on this group. This new version is very different from its predecessor and in particular includes a new approach to wind loading, which is critically dependent for safety on competent management of events.
The Minister, Nick Raynsford, MP, in his opening speech stated that the safety of spectators was a primary consideration. Many structures would be exempt from the Building Regulations, as they would be erected less than 28 days. The assumption behind the exemptions was that structures would be less complex and would involve small numbers of people. These assumptions were not always valid and some highly complex structures are erected with large numbers of people. In safety aspects effective management was also important and beyond the scope of the Building Regulations. Legislation could not do everything and this guidance document would help in ensuring safety.
Dr Sam Thorburn, chairman of the monitoring group, said that safety for these types of structures was heavily dependent on self-regulation. Responsibility lies with the Client for safety. They must ensure that competent persons are employed. People must not only be safe they must feel safe. Risk assessment was vital. What is the risk? How likely is it to occur? What are the consequences of failure?
Roger Barrett, Star Hire (Event Services) Ltd., said on behalf of the Production Services Association that this was a document to be proud of as it gives clear guidance to all be they contractor, event organizer, designer, manufacturer, enforcement staff, and structural engineers. He then showed a series of slides to show a large number of failures and potential failures. These related to failures where: -
The common links in these failures was:-
A Matria, Health and Safety Executive, said that society allows lawyers to lose cases, but demands that structures do not collapse. The Health and Safety at Work Act of 1974 puts a heavy responsibility on managers in Sections 2 and 3. The CDM 1994 Regulations requires designers to eliminate risk where possible, mitigate the effects of risk, and to ensure relevant information is given to the contractor.
The main hazards giving rise to risk are: -
There are 3 recurring themes of structural failures: -
The HSE does not enforce on many temporary sites but may well be available for advice.
Dave Baker, formerly Head of Building Control at the London Borough Richmond, said this guide is an improvement over the "Green Guide" in that it gives a detailed chapter on Statutory Control.
In many ways the exemptions from control under the Building Regulations are very unsatisfactory. The Local Authority has the power in many cases to prohibit the use of a structure, if they know about it and that there is a danger to the public. If they are approached for advice on a structure exempt from control, however, Local Authority Lawyers demand that no liability be attracted to the Authority by the giving of any such advice.
The Advice given on Legislation includes for Scotland and Northern Ireland. A Local Authority Head of Building Control in Scotland gave this advice. Some discussion on the merits of the Scottish system of control over that in England and Wales came from the audience. Big city venues, however, are more likely to have knowledgeable specialist staff than other parts of Scotland.
Dr Nick Cook, Wind Engineering Consultant, outlined the new method for assessing wind load. It is based on active safety management. This method is already in use for the operation of tower cranes.
There are 2 options for wind load safety design in Section 8:-
Option A
Option B
(Event would probably not take place at this wind speed anyway);
Detailed use of the guidance was then given for different structures. If a stand is liable to topple the holding down load is reduced as people leave. It is better to evacuate such a structure earlier rather than later.
A shipping forecast of "Force 5 Force 7 imminent" is when to start getting worried.
Dr John Dougill, Chief Executive of the Institution of Structural Engineers, explained that for grandstands, adequate stiffness is needed to control dynamic movements. Bracing is needed to control vertical and horizontal movements. In various discussions with the audience it was stated that some arrangements of bracing were four times as stiff as other arrangements at no additional cost.
| Typical arrangement of bracing. | This arrangement of the bracing is the best, being 4 times stiffer |
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Some members of the audience mentioned that installers sometimes left out horizontal plan bracing, as it was less easy to understand its importance. Vigilance by checkers was needed to ensure safety.
Other members of the audience mentioned that: -
Mr. Mike Bunting, Made Up Textiles Association, said that their Associations’ self regulatory scheme provided an audit trail for flame retardant tent materials. Only Approved Material Suppliers were used and MUTA members are required to follow their code of practice. MUTA carry out site inspections to ensure that submitted samples are used in practice. Testing is done of different material types and they have a database of how materials perform as the materials age. Their objective is to improve standards. Operatives are trained to NVQ Level 3 and a list of certified members appears on their web site.
Mr. Blakeman, Clarke Nicholls & Marcel Consulting Engineers, outlined with slides 2 story, 3 story, and 4 Story temporary buildings erected as temporary structures. These were big buildings with large numbers of spectators. The approximate size of the 4-story building was 110m long by about 14 m wide. If it was a permanent building it would cost about £1.5m but as a temporary structure it could be taken down and be re-erected elsewhere. As a modular structure, the internal arrangement and size is flexible for each client’s needs.
One of the problems encountered is that as staff are taken on for each event it is difficult to ensure they are adequately trained in safety. Problems encountered included finding calor gas cylinders stored next to a rear exit of the building. Someone smoking in this vicinity could cause an explosion. The natural place for staff to smoke is of course at the rear of the building.
Other problems found included a lack of a balustrade handrail at first floor level on the 2-story building. The structure here was like a tent only at first floor level. While Plastic vision panels in a tent wall are safe at ground level, at first floor level a barrier needs to be provided.
Mr. John Cowan, Geoffrey Hunt & Partners, summed up by stating that everyone needs to take responsibility for the part they play. It is important that Clients are clearly informed of their responsibility to employ competent persons and that the legal liability for safety may well be theirs. Risk analysis has to happen for every project. A new safety plan is required each time. Event Organizers should consider themselves to be the client. The new guide clearly states which sections need to be read by Clients, Venue Owners, Event Organizers Designers, Contractors, Suppliers and those who supervise, inspect, and monitor these structures.
"Temporary demountable structures Guidance on design, procurement and use" SECOND EDITION is published by The Institution of Structural Engineers, 11 Upper Belgrave Street, London, SW1X 8BH. Price £35:00
Robert Hunter-Jones MSc, MICE, MIStructE, FIBC
(Institute of Building Control Representative on "The Temporary Demountable Structures Implementation Monitoring Group").
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