A risk based framework for performance based fire safety design of steel and composite structures

For the development of performance based design on a proper scientific basis the use of the concepts of risk and reliability is inevitable. The application of the concept of performance based design is not simple because of the large ranges of probability and consequences of events which exist. While this concept poses major challenges, it also offers enormous opportunities because of the inherent element of choice. Traditional performance based design methodologies approach the design of structures for accidental loading linearly. Experience, however, suggests that the risk posed by fire is not quantifiable without direct reference to the actual structure. Whilst this can be achieved to some degree of satisfaction in an ad-hoc manner, a systematic deterministic approach is proposed here for fire safety design, as an alternative to linear methodologies or less robust ad-hoc treatments. A design is separated into regions, non-exclusive of one another, which are classified according to a 'risk level' based upon the type of structure and the surrounding regions. Fires of concern are identified, and the probability of occurrence of each of these fires is calculated along with the consequences to the structure. Using a 'risk matrix', regions of higher risk are identified and re-iterated to reduce the risk to an acceptable level