轴向约束混凝土短柱受火后抗震性能试验研究

Experimental study on seismic performance of axially-restrained concrete short columns after fire

为研究高温下混凝土短柱的持荷和端部轴向约束对受火后混凝土短柱抗震性能的影响,进行了10根受火1 h后混凝土短柱和2根未受火对比柱的拟静力试验,分析了轴向约束、持荷、轴压比和剪跨比等因素对受火后混凝土短柱的破坏形态、峰值荷载、延性和耗能的影响。结果表明:高温下未持荷短柱、高温下持荷短柱和高温下轴向约束短柱受火1 h后峰值荷载均显著降低,是未受火时的67.7%~75.3%。高温下初始轴压比为0.2时,高温下轴向约束短柱、高温下持荷短柱的高温后峰值荷载分别为高温下未持荷短柱的92.0%~99.9%、99.5%~102.2%。随着轴压比的增大,高温下轴向约束混凝土短柱的附加轴压力减小,高温后受剪承载力增大。当受火时间不超过1 h且轴压比不超过0.3时,受火后混凝土短柱的受剪承载力评定可不考虑高温下持荷和轴向约束的影响。

To study the effects of the sustained load and the end axial constraint of concrete columns during fire on their seismic performance after fire,the quasi-static tests of ten concrete short columns after exposure to fire for one hour and two comparison specimens without fire were carried out. The influences of the axial constraint,sustained load,axial load ratio,shear span ratio on the failure mode,peak load,ductility and hysteretic energy dissipation of concrete short columns after fire were investigated. The results show that: the peak load of the concrete short columns without sustained load,the concrete short columns with sustained load,and the concrete short columns with axial constraint after one-hour fire is clearly decreased,about 67. 7%-75. 3% of that without fire; when the initial axial load ratio is 0. 2,the peak load of the specimens with axial constraint and with sustained load during fire is respectively about 92. 0%-99. 9% and 99. 5%-102. 2% of that without sustained load. With an increase in axial load ratio,the additional axial pressure of the axially-constrained concrete short column during fire is declined,and the shear strength after fire is increased. When the fire exposure time is less than one hour and the axial load raio is less than 0. 3,the effects of sustained load and axial constraint during fire can be neglected for the evaluation of the shear strength of concrete short columns after fire.