火灾后混凝土短肢剪力墙抗震性能的试验研究

Experimental study on seismic performance of concrete short-limb shear walls after fire

通过对6榀火灾后混凝土短肢剪力墙试件和1榀未受火对比试件的拟静力试验,研究受火时间、轴压比、暗柱和暗支撑的设置对混凝土短肢剪力墙的破坏形态、承载力、刚度、延性比、骨架曲线、滞回耗能等性能的影响。利用Park损伤评价模型对受火前后短肢剪力墙的抗震性能损伤进行评估,提出一种能反映火灾高温对短肢剪力墙抗震性能损伤加大程度的评价指标。借鉴规范的常温下混凝土剪力墙抗剪承载力的计算方法,建议四周受火后混凝土短肢剪力墙抗剪承载力的计算公式。结果表明:火灾后短肢剪力墙的承载力随受火时间的增加而降低。轴压比为0.2的短肢剪力墙受明火60min、120min后,承载力较未受火时分别降低7.3%、19.6%。轴压比可提高火灾后短肢剪力墙的承载力。受明火60min后,轴压比为0.2、0.3的短肢剪力墙的承载力分别较轴压比为0.1时提高24.6%、51.7%。暗柱和X形暗支撑均可提高火灾后短肢剪力墙的刚度和耗能,但暗柱不会提高承载力,而后者对承载力有提高作用。受火前后短肢剪力墙的滞回规则明显不同。

Based on quasi-static tests of six concrete short-limb shear walls after fire and one contrastive specimen without experiencing fire, the effects of fire exposure time, axial load ratio, concealed column and concealed bracing on the failure mode, bearing capacity, stiffness, ductility ratio, skeleton curve and hysteretic energy dissipation were studied. The damage in seismic performance of the specimens before and after the fire was evaluated based on the damage assessment model proposed by Park, and furthermore an assessment index for evaluating the increased damage in seismic performance of short-limb shear wall induced by fire was proposed. A calculation formula for shear bearing capacity of concrete short-limb shear wall after exposing all its sides to fire was developed by referring to the calculation method at ambient temperature specified in code. The results show that the strength of short-limb shear wall may be decreased with the increase of fire exposure time. After experiencing fire for 60rain and 120min, the bearing capacity of short-limb shear wall with the axial load ratio as 0.2 may decrease 7.3% and 19.6% , respectively. It is noteworthy that the axial load ratio has a positive effect on the improvement of bearing capacity of short-limb shear wall after the fire. After experiencing fire for 60rain, the bearing capacity of short-limb shear wall with the axial load ratio as 0.2 and 0.3 increases 24.6% and 51. 7% , respectively, compared to that with the axial load ratio as 0. 1. The stiffness and hysteretic energy dissipation of short-limb shear wall after the fire can be increased by concealed column and X-shape concealed bracing. The former can＇ t improve the bearing capacity, while the latter is helpful to the bearing capacity. In addition, the hysteretic rules of concrete short-limb shear wall after the fire are remarkably different from those at ambient temperature.