عنوان مقاله [English]
Post-earthquake fire (PEF), is one of the rare incidents with dangerous consequences. Under fire loads, structural strength, structural stability and failure of elements in intact structures are different from the damaged structures. The aim of this study is to investigate the sensitivity of a 7-story RC frame failure time to random variables during post-earthquake fire loading. For this purpose, the sensitivity of a RC frame in post-earthquake fire loading has been investigated by FOSM analysis method. The seismic load in different Sa has been applied to this frame for a particular earthquake loading, and fire load has been applied after each Sa. The results of this analysis show that in low-intensity seismic load, armature yield stress and concrete cover have the greatest impact on RC frame failure time in post-earthquake fire. As Sa increases, the sensitivity of the structural failure time to concrete cover parameter decreases. The yield stress of the armature is almost the most sensitive random variable in PEF intensities. Concrete strength and dead load are also one of the most sensitive random variables in this scenario. The modulus of the elasticity of the reinforcement and the length of the span (in the case of ignoring the reinforcement cover) produces the least sensitivity for failure time in RC frame under PEF loading. The results show that Sa increases the rupture time sensitivity to random variables. The results show that, with increasing Sa, the sensitivity of the failure time to random variables is decreased. In the next step sensitivity analysis for 10 earthquake records is performed. The results show that the seismic load in RC frames (in contrast to the steel frame) gives the most sensitivity to the failure time in PEF loading. For example, in Sa = 0.7g, response swing (mean ± two standard deviations) for a failure time was calculated 145 minutes, While the greatest swing for reinforcement yield stress, concrete cover and concrete strength was calculated 60, 53 and 40 minutes, respectively.