Abstract :
[en] Fire brigades face a major threat when intervening in a building in fire: the possibility of structural collapse during the cooling phase of the fire, or soon thereafter. Currently this threat is amplified by the fact that the behaviour of structures after the time of peak gas temperature is not well understood, and is not taken into account in the design. This work presents an analysis of the behaviour of different structural members under natural fires and develops a method to characterize their sensitivity to fire decay phases. Thermo-mechanical numerical simulations based on the non-linear finite element method are conducted using the parametric fire model of Eurocode to represent natural fires. Results show that, for all the studied members (column, beam) and materials (reinforced concrete, steel and timber), structural failure during or after the cooling phase of a fire is a possible event. The major factors that promote delayed structural failure are the thermal inertia and the constituting material of the member. A method, based on a new indicator, is proposed to quantify the propensity to delayed failure for structural members under natural fire. This work enhances the understanding of the structural behaviour under natural fires and has important implications for the safety of the fire brigades and people proceeding to a building inspection after a fire.
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