Abstract:
Based on cyclic reversed loading tests of four steel reinforced concrete (SRC) beam-column joints after exposure to fire and two comparative joints at ambient temperature, the hysteresis behavior, ductility, energy dissipation, load bearing capacity and stiffness degeneration of such composite joints after exposure to fire were studied. Influences of fire exposure time and axial compression ratio on seismic behavior of the samples were analyzed. Test results show that failure patterns of SRC beam-column joints after exposure to fire are similar to that at normal room temperatures. After fire damage, SRC beam-column joints have plumper hysteresis loops, lower load bearing capacity and ductility coefficient and exhibit more significant deformation. With the increase in fire exposure time, the degree of load bearing capacity degeneration and deformation increase rises, and ductility coefficients decline. Under cyclic reversed loading, the strength of SRC beam-column joints degenerates, and the degeneration coefficients decrease with the increase in displacement in the early stage of loading, but generally remain stable in the later stage of loading. This reflects good ability of resistance to cyclic loading. Compared with specimens subject to normal temperature, specimens after exposure to fire have lower initial stiffness and higher equivalent damping ratio. With the increase in fire exposure time, the degree of initial stiffness degeneration falls, and equivalent damping ratio increasing rises. With the progress of loading, the stiffness of specimens after exposure fire tends to be close and the equivalent damping ratio tends to be lower to that at normal temperature. Moreover, the degree of equivalent damping ratio decrease rises with the increase in fire exposure time at this stage. The axial compression ratio has a certain influence on the seismic behavior of SRC beam-column joints after exposure to fire. With the increase in the axial compression ratio, the strength and stiffness increase, but ductility coefficients decrease to some degree.