火灾后型钢混凝土梁柱节点抗震性能试验研究

通过4个火灾后型钢混凝土柱-型钢混凝土梁节点试件及2个常温未受火对比试件的低周反复加载试验，研究火灾后该类节点的滞回特性、延性、耗能性能、承载力与刚度退化规律，分析了受火时间、轴压比对火灾后该类节点的抗震性能的影响。结果表明：火灾后试件与常温未受火试件的破坏过程和破坏形态基本一致。经历火灾损伤后，型钢混凝土梁柱节点的滞回曲线仍然饱满，但试件承载力降低、变形增大、延性减弱，受火时间越长，承载力下降程度越高、变形增加程度越大、延性系数越小。反复荷载下型钢混凝土梁柱节点的强度出现衰减，加载初期的衰减系数随位移的增大而减小，加载后期的衰减系数随位移的增大总体保持稳定，体现出良好的抗荷载循环能力。与常温未受火试件相比，高温后试件加载初期的刚度降低、等效阻尼比增大，受火时间越长，刚度降低和等效阻尼比增大的程度越高。随着加载的进程，高温后试件的刚度与常温未受火时间刚度逐渐趋向一致，但等效阻尼比相比常温未受火试件减小，受火时间越长，减小程度越高。轴压比对火灾后节点的抗震性能产生一定影响，随着轴压比的增大，试件强度和刚度有所提高，但延性下降。

EXPERIMENTAL STUDY ON SEISMIC PERFORMANCE OF STEEL REINFORCED CONCRETE BEAM-COLUMN JOINTS AFTER EXPOSURE TO FIRE

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.