Post-fire seismic performance of steel-reinforced concrete frames: Experiment

Considering the combined effect of fire and loading, experimental studies were conducted to investigate the mechanical properties during the heating and cooling phases as well as the post-fire seismic performance of steel reinforced concrete (SRC) column-reinforced concrete (RC) beam planar frame structures. The experiments focused on studying the temperature and deformation changes of the frame structure during the heating and cooling process, as well as the post-fire bearing capacity, hysteresis curve, stiffness, ductility, and damping coefficient. The research results showed that the deformation of the frame increased compared with the pre-fire condition, indicating that the stiffness of the frame decreased after heating and cooling. The residual deformation in the out-of-plane direction caused the failure of the frame during the post-fire seismic test, and the residual deformation and concrete spalling reduced the post-fire seismic load bearing capacity of the SRC column-RC beam-frame structures. Under horizontal cyclic loading after fire, the concrete at the bottom end of the column was gradually crushed, leading to the formation of plastic hinge, while noticeable shear and bending deformations occurred at the beam end near the beam-column joint region, eventually resulting in structural failure. The frame specimens after fire exhibited a lozenge-shaped hysteretic loop under horizontal load - horizontal displacement, characterized by the fullness of the hysteretic loop and the strong energy dissipation capability. Compared with the unheated specimen, the load bearing capacity of the fire-exposed frame specimens was reduced by thirty percent, and the stiffness at a horizontal displacement of 2 mm was reduced by thirty eight percent.