Performance of steel-reinforced concrete column after exposure to fire : FEA model and experiments

This paper studies the postfire performance of steel-reinforced concrete (SRC) columns subjected to an entire loading and fire phase, including ambient temperature loading, heating and cooling with constant external loads, and postfire loading. A sequentially coupled thermal-stress analysis module was employed in a finite-element analysis (FEA) program to establish temperature field analysis and structural-analysis models of SRC columns subjected to the entire loading and fire phase. To improve the precision of the FEA model, the influence of fire-induced concrete explosive spalling (CES) was considered by using element change technique. Besides the existing fire resistance test data of SRC columns, to further validate the accuracy of the FEA model in the postfire phase, a set of fire tests on SRC columns, including a fire-resistance test and postfire test subjected to the entire loading and fire phase, were conducted. Compressive failure and bending failure were observed in the test. Comparison between predicted and test results indicates that the accuracy of the FEA model was acceptable, and then the FEA model was extended to simulate a full-scale SRC column in a real project subjected to the entire loading and fire phase. The temperature distribution, load versus axial deformation relations, and load redistribution of the full-scale SRC column during the entire loading and fire phase were investigated. It was found that the postfire peak load of the calculated column can be 26.7% lower than that at ambient temperature. The load carried by shaped steel rises from 20% to the peak value of 93% during the heating and cooling phase, indicating the significant contribution of shaped steel to resist the external loads during fire exposure.