Update on fire design This month's special report looks at developments in fire engineering, ideas in progress and design resources BY ARUP FIRE
The role of fire engineering in building design is developing rapidly, write Barbara Lane and John Munro. We are reaching a significant stage, the result of progress on several fronts. In principle, the increased flexibility provided by the functional/performance- based approach to safety design is being adopted internationally and is resulting in heavily revised national regulations and codes of practice. The draft British Standard on fire safety engineering, bs dd240: Part 1: Guide to the Application of Fire Safety Engineering Principles, should emerge as a full bs in the next couple of years.
Prescriptive uk fire codes are also going through a major rationalisation, leading to one bs covering all the guidance currently spread over the bs 5588 series and the publications of all the government departments and agencies with an interest in fire, such as the detr, Home Office and Scottish Office.
Protecting large spaces
The creation of large open spaces within buildings sets new challenges for fire safety engineering. These often public spaces, where people will be unfamiliar with their surroundings, have longer escape distances and larger volumes than conventional fire safety guidance would recommend. Work on examples such as the Eden Project at St Austell and the ExCeL exhibition development in the Royal Docks, London, has highlighted the importance of commitment to building management, the training of staff, and the reliability of data for use in model calculations for fire and smoke spread.
With the move towards enclosing what are in effect small towns, attitudes to management of fire will need to change. Most commercial buildings with atria or similar voids are managed through maintenance regimes and simple staff rules, such as banning smoking, though this is changing to include training of security and attendant staff to deal with emergencies. Stewards and controllers are becoming more important for co-ordinating evacuation with minimum disruption. In the case of ExCeL, it will be necessary to ensure the safe evacuation of the 47,000 people from the exhibition halls.
Data for simulation
Validation data in fire engineering is continually improving, covering, for example, people movement, fire- and smoke-spread, smoke control and fire safety response times, matched to the scale and flexibility in use of the spaces being designed, with the promise of opening up new design possibilities. It should become acceptable to implement:
unprotected structural steel internally. Data on real fire conditions are needed to show that steel's intrinsic fire resistance is adequate. Research is under way on a full-scale building frame at bre's Cardington laboratory
lift evacuation, and optimisation of stair provision, in tall buildings
increasing compartment sizes, entailing the management of fire load to reduce fire risk
reducing fire brigade access requirements using automatic fire control and suppression.
Designers are interested in making fire features unobtrusive, both visually and functionally. Often, fire safety systems can be blended into a building by taking advantage of other aspects of its design. For example at Liverpool Street Station, smoke ventilation beneath the Broadgate deck uses natural ventilation via the adjacent Victorian railway train shed, originally designed for steam engines. In the hactl project in Hong Kong (opposite), filling the atrium roof structure with water provides both structural fire resistance and a sprinkler distribution pipework. In such examples fire safety design has exploited another design feature.
It is fashionable to talk about risk assessment in fire safety circles, and especially quantified risk assessment, writes David Charters. qra - established as a safety assessment tool in industry generally for some time - is the process of applying a probability to an initiating event and to each successive potential failure leading to an unacceptable consequence. For fire, failures might be in systems - detectors, protection or sprinklers - or in management and training. Unacceptable consequences might be loss of life, financial cost or length of functional disruption. As a design tool, qra gives a measure of the effectiveness of any part of a safety system design.
Forthcoming revisions to bs dd 240 and the Fire Precautions (Workplace) Regulations include stronger reference to qra techniques.
Although member states will continue to be ruled by national fire regulations, they will all feel the effect of the harmonisation of product standards, writes Anthony Ferguson. In the near future, references to the various parts of bs476 on fire resistance and reaction to fire testing will give way to en references (European Norms).
Fire resistance will still be described in terms of minutes - 30, 60, 90 etc - but in some areas, notably fire doors, a complicated set of suffixes and prefixes will be used to identify other aspects of performance.
Most tests and all the nomenclature on reaction to fire will change. The detr and the Scottish Office have still to decide exactly how the new palette of tests and classes will be used, but aim to change the actual level of performance required as little as possible.
There have been several major professional developments in response to the increasing need for a fire safety design discipline, writes Margaret Law. On the accreditation front, the IFireE (Institution of Fire Engineers) has established an Engineering Council Division aimed at chartered engineers. Such design consultants will promote the significance of fire safety engineering within the industry.
Arup Fire, Ove Arup and Partners