Keywords: risk analysis, fire safety engineering, performance based fire safety design, hazard identification, risk scenarios, fault tree analysis, computational tools.

The problem of structural fire safety, which has a long history, recently gained a predominant position in engineering design. This is because nowadays, always bigger and more complex structures are designed and built, making use of particularly fire sensitive materials such as steel, and also, because there is an increasing belief that structures not only have to resist to the design loads, but to maintain a minimal performance in accidental situations as well.

In the first part of this study, the system part of the design for fire safety is addressed. The main focus is on the risk analysis requirements and methods, as prescribed in many international codes and standards [1,2,3] related to the performance based approach to fire safety. The starting point is an analysis of fire scenarios to determine which design alternatives will meet those fire safety goals, either those related to the structural performance or to the performance of the system in general

In the second part of this study, concepts of risk analysis for fire safety are presented, indicating the steps of the risk analysis process. The theoretical arguments exposed, find a practical exemplification in the fire risk assessment of a complex structural system. The object under consideration is a steel frame industrial facility, used for the storage and maintenance of helicopters. This facility presents an elevated fire risk.

The evolution of the fire is simulated with a commercial finite volume method (FVM) software [4] on the basis of the characteristic parameters of the materials present within the fire domain. Two particular phenomena are considered and further developed:

• smoke and fire evolution in time;
• smoke and fire evolution in space.

In order to evaluate the smoke and fire expansion and evolution, the temperature pattern inside the facility is inquired at specific time points. The results are presented in a graphic depicting the temperature pattern in a "vertical slice" of the facility, in proximity to the flaming helicopter, for different venting scenarios. Further results are obtained by observing the temperature evolution, at a point near the fire ignition for the three cases considered

It is shown that only with a faithful representation of the system, a truthful definition of fire scenarios and detailed advanced analysis, it is possible to have a clear view on the consequences a fire has, both directly to the structure and indirectly, in terms of smoke diffusion.

1

International Standards Organization (ISO) TR 13387-1, "Technical report on Fire Safety Engineering", 1999.

2

ISO/TS 16732, "Fire Safety Engineering - Guidance on fire risk assessment", 2005.

3

ISO/PDTS 16733, "Fire Safety Engineering- Selection of design fire scenarios and design fires", Committee draft 2005.

4

NIST (National Institute of Standards and Technology), www.nist.gov.

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