高温后钢筋混凝土短柱抗震性能试验研究

Experimental study on seismic performance of reinforced concrete short columns after fire

通过对7根高温后钢筋混凝土短柱试件和1根常温对比试件的拟静力试验,研究受火时间、轴压比和剪跨比对火灾后钢筋混凝土短柱的破坏形态、受剪承载力、骨架曲线、刚度退化、延性比、滞回耗能等的影响。利用有限元程序计算了高温后截面混凝土抗压强度的平均折减系数,提出了四周受火后钢筋混凝土柱受剪承载力的计算方法。研究结果表明:高温后短柱的受剪承载力随受火时间的增加、剪跨比的增大而减小;剪跨比对受火前后受剪承载力影响变化的程度相差较小;高温后短柱的受剪承载力先随轴压比的增大而增大,但当轴压比增大至界限轴压比后,受剪承载力反将降低,且高温后柱的界限轴压比较未受火时有减小趋势;提出的高温后钢筋混凝土柱受剪承载力计算式具有一定的安全保证率,可用于火灾后该类构件受剪性能的损伤评定。

Based on the quasi-static tests of seven reinforced concrete （RC） short columns after fire and one contrastive specimen at ambient temperature, the effects of fire exposure time, axial load ratio and shear span ratio on the failure mode, shear strength, skeleton curve, stiffness degradation, ductility ratio and hysteretic energy were analyzed. The average reduction coefficient of compressive strength in concrete sections was calculated by a finite element program, and a practical calculation method for the shear strength of RC columns after exposure to fire on all sides was proposed. The results show that： the shear strength of short columns decreases with the increase of fire exposure time and shear span ratio. The difference of influence degree of shear span ratio on the shear strength of columns before and after fire is small. With an increase of axial load ratio, the shear strength of short column after fire firstly is increased and then decreasing. The critical value of the influence of axial load ratio on the shear strength of columns after fire is less than that at ambient temperature. The proposed formula for the residual shear capacity of RC columns after fire has certain safety margin ratio, and can be used to assess the shear performance of that member after fire.