考虑初始荷载的火灾后RC柱抗震性能

Seismic Performance of Post-fire RC Columns with Pre-load

为研究初始荷载作用对火灾后钢筋混凝土(RC)柱抗震性能的影响,分别对3根高温后RC柱和2根常温对比试件进行滞回加载试验。比较分析了不同初始荷载作用下试件的温度场变化、滞回曲线、骨架曲线和破坏模态,重点研究了不同初始荷载与高温冷却全过程对钢筋混凝土柱的破坏模态、剩余变形、剩余承载力、抗弯刚度与延性以及耗能能力的影响。结果表明:初始荷载作用对钢筋混凝土柱高温后的抗震性能影响显著,且存在一定尺寸效应;初始荷载作用时,随着轴压比增大,高温后试件的破坏模态由弯曲破坏变为压溃破坏;初始荷载的作用不仅影响柱截面温度场,而且使得高温后试件产生剩余压缩变形,轴压比越大,剩余压缩变形越大,剩余承载力和抗弯刚度均呈增大趋势,而延性和耗能能力呈下降趋势;高温冷却作用使得试件的承载力、抗弯刚度、延性以及耗能能力总体呈现不同程度的退化;建议在对受火后钢筋混凝土柱进行损伤评估和抗震性能研究时,应合理考虑初始荷载作用和尺寸效应的影响。

In order to study the effects of pre-loads on the seismic performance of post-fire reinforced concrete(RC) columns, the cyclic loading tests were carried out on three RC columns after high temperature and two specimens at room temperature, respectively. By comparing and analyzing the variation of temperature field, hysteresis curve, skeleton curve and failure mode of specimens under different pre-loads, the effects of different pre-loads and high temperature cooling process on failure mode, residual deformation, residual bearing capacity, flexural stiffness and ductility, and energy dissipation capacity of reinforced concrete columns were emphatically studied. The results show that the effect of pre-load on seismic behavior of reinforced concrete columns after high temperature is significant, and there is a certain size effect. When the pre-load is applied, with the increase of the axial compression ratio, the failure modes of specimens change from bending failure to crushing failure after high temperature. The pre-load not only affects the temperature field of the column section, but also causes the residual compressive deformation of the specimen after high temperature. The larger the axial compression ratio is, the larger the residual compression deformation is, the larger the residual bearing capacity and flexural rigidity are, while the ductility and energy dissipation capacity show a downward trend. High temperature cooling makes the bearing capacity, flexural rigidity, ductility and energy dissipation capacity of the specimens degenerate to varying degrees. It is suggested that the influence of pre-load and size effect should be reasonably considered in damage assessment and seismic performance study of reinforced concrete columns after fire.