Post-fire seismic performance of reinforced concrete structures

In this study, the seismic performance of a reinforced concrete (RC) structure with 4 stories and 4 spacings exposed to high temperatures was presented. Four different fire duration, i.e., 30, 45, 60, and 90 min and different fire locations were considered. In order to obtain the temperature distributions in the cross-sections of the RC members, thermal analyses were carried out under ISO-834 standard fire curve. The mechanical and thermal properties of the materials were also obtained. Then, sectional analyses were performed for the RC members to obtain the load-deformation relations. Finally, the nonlinear static analyses were conducted after fire exposure to obtain capacity curves, and the seismic performance of the structure was evaluated by transforming the capacity curves into the capacity spectra. It was found that when the temperature level increases, the mechanical and thermal properties of materials reduce especially after 4000 C. The results show that exposure to high temperatures leads to a significant decrease of about 75% of the load-carrying capacity of a structural member after 90 min. The results also show that when the fire duration increases, the base shear forces, and the roof displacements systematically decrease for all floors. The decrease rate in the base shear forces and the roof displacements was approximately up to 60%. The fire location also affects the system response. It was observed that the global structural response for elevated temperatures followed a gradual reduction in capacity with an increase in temperature levels.