ADVANCED ANALYSIS OF STEEL FRAMEWORK EXPOSED TO ACCIDENTAL FIRE

This paper describes the use of advanced analysis which accounts for both material and geometric nonlinearity to assess the performance of the steel structures exposed to natural compartment fire. The analysis requires only one line element per physical member of the structure to obtain a realistic representation of the global non-linear effects of the structure. The transient heat transfer is computed using a refined finite element mesh. The accuracy of the proposed advanced analysis is validated and its advantage over the conventional prescriptive approach in fire-resistance design is demonstrated. Natural fire curve is used in contrast to the ISO standard fire, representing the real fire development in the compartment. The simulation of natural fire time-temperature curve is according to the latest Eurocode prEN 1991-1-2 (released in July 2001) which provides a simplified but reasonable way to derive the parametric compartment fire curves based on several fundamental parameters such as fire load, ventilation factor and properties of surrounding surfaces. Performance-based assessments are carried out on 3D multi-storey frames subjected to natural compartment fire. The computed results are compared to those from the conventional approach based on ISO standard fire curve and the advantage of the advanced analysis is highlighted. The effect of fire load and ventilation on the structural response of the frames is studied and the worst fire scenarios are identified. The design implications on the requirement of fire protection are discussed