Numerical Investigation of the Post-Fire Performance of Steel Columns

Research on the seismic performance of steel structures has led to the development of improved structures, which minimize structural and non-structural damage and can be reused immediately after an earthquake. Moreover, significant advances have been made for predicting the response of steel members, connections, and structural systems exposed to fire. Nevertheless, the research on the reuse of steel structures after a fire event is limited. A steel structure designed according to the current seismic codes can survive a fire without significant structural damage and may be repaired and reused. Therefore, it is of great importance to study whether the reuse of steel structures after a fire is safe in high seismicity areas. This paper investigates the seismic performance of steel columns that are pre-damaged due to fire. For this purpose, sophisticated finite element models have been developed and validated against experimental data. It was concluded that the models accurately predict the behaviour of beams-columns at elevated temperatures. First, the behaviour of the columns was studied using simplified boundary conditions; the surrounding structure was not included in the numerical model. Thermal-structural analyses were performed to determine the structural damage induced by the fire. Subsequently, the cyclic performance of the columns was investigated, considering both the residual post-fire deformations and the proper material properties. Aiming to obtain more realistic results, the complicated interaction between the heated columns and the surrounding structure was considered in the modelling. For this reason, the fire behaviour of a seismic resistant frame was simulated. Then, the behaviour of fire-damaged columns under cyclic loading was assessed. The analysis of the results demonstrates the effect of the post-fire damage on the cyclic behaviour of columns.

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