Reinforced concrete (RC) structures may suffer fire, earthquake, and other loads during their life cycle. The coupled disasters will lead to further deterioration and damage to structural performance, which has attracted the attention of many researchers. This paper established a series of three-dimensional finite element models of RC columns subjected to simultaneously combined fire and cyclic loads and investigated the seismic performance of the RC column during fire exposure. The models considered mechanical properties degradation of reinforcement steel, concrete, and the nonlinear bond strength‐slip behavior at elevated temperatures. After verifying the numerical model through the skeleton curve and damage character, the hysteretic energy dissipation, ductility, and other seismic parameters of the RC column subjected to simultaneously combined fire and cyclic loads were systematically analyzed. The results show that the severely damaged region of the RC column gradually shifts from the bottom to the middle of the RC column with fire duration increases. The fire duration can improve the yield displacement but reduce the hysteretic energy dissipation and the peak force of the RC column. The ductility of RC columns during fire exposure is smaller than that at room temperature except for the working conditions with a short fire duration and the axial load ratio that is not greater than 0.3. To avoid the excessive seismic performance degradation and buckling failure of the RC column during fire exposure, the recommended limit value of the axial load ratio used in this paper is 0.3.

Reinforced concrete (RC) structures could suffer from the combined action of fires, earthquakes, and other loads during their life cycle; more importantly, coupled disasters lead to further deterioration and damage to structural performance. This paper investigated the multiple performances and distinguished the safe working conditions of the RC column subjected to simultaneously combined fire and cyclic loads. The numerical model considered the degradation of the mechanical properties of steel and concrete and the bond-slip performance between steel and concrete at high temperatures. The results show that the performance of RC columns with different section sizes, longitudinal reinforcement ratios, cover thicknesses, axial load ratios, and cyclic loads differs greatly under simultaneously combined fire-cyclic loads. In specific, when the cyclic load application time is less than 2 h, the cyclic load has little effect on the response of the RC column. According to the different characteristics of RC columns when subjected to combined fire-cyclic loads, the firing process of RC columns is divided into four stages. To avoid the excessive performance degradation of RC columns, the minimum designed fire resistance time of RC columns is recommended to be 2.5 times the fire resistance time of the RC column under static loads.

为分析长时间火灾诱发的地铁车站结构损伤情况,利用PyroSim火灾模拟软件对地铁列车发生长时间火灾时地铁车站的温度场进行了模拟,基于温度场进行了传热分析,通过定义损伤度对地铁车站结构进行了损伤分析.结果 表明:由于羽流流动等原因,经历长时间火灾后地铁车站结构不同位置处的损伤度差异明显.近火源处站台层墙表面及墙内钢筋受到不同程度的损伤,墙表面损伤严重,损伤度达到0.7,远火源处及站厅层墙面几乎没有损伤;站台层柱中部及顶部的角部钢筋损伤度为0.04～0.24,而站厅层柱钢筋的损伤度均小于0.1,所有柱的混凝土损伤度小于0.13;上板、中板和下板的混凝土及钢筋损伤度均为0;站台层中梁钢筋和混凝土有一定的损伤,对于站厅层,顶梁的混凝土及钢筋损伤度约为O;通过定量分析所得的损伤度可以为火灾后的加固补强提供依据.