冻融损伤低矮钢筋混凝土剪力墙恢复力模型研究

Restoring force model of freezing-thawing damaged squat reinforced concrete shear walls

为研究严寒地区钢筋混凝土剪力墙的力学性能,对经历冻融循环作用的8片低矮钢筋混凝土剪力墙进行了拟静力试验研究。综合考虑冻融循环次数、混凝土抗压强度和轴压比对剪力墙承载力和延性的影响,以动弹性模量定量表征混凝土冻融损伤程度的冻融损伤变量D,建立剪力墙的骨架线特征点荷载（位移）修正系数计算模型。考虑累积损伤效应造成的承载力和刚度退化,引入循环退化指数βi,提出了适用于遭受冻融循环的低矮钢筋混凝土剪力墙的滞回规则,进而建立了考虑冻融循环损伤作用的低矮钢筋混凝土剪力墙恢复力模型。选取4榀经历不同冻融循环次数的低矮钢筋混凝土剪力墙验证该恢复力模型的准确性,计算其滞回曲线和累积滞回耗能值并与试验值进行对比,吻合情况较好。研究所建立的恢复力模型具有较好的精度,可为严寒地区剪力墙结构的弹塑性分析提供理论依据。

In order to study the mechanical properties of RC shear wall in severe cold area, the results of the quasi- static tests of eight RC shear walls under freezing-thawing cycles were analyzed. Considering the impacts of the number of the freezing-thawing cycles, the concrete compressive strength and axial load ratio on the strength and the ductility of squat RC shear wails, the correction coefficient calculation model of characteristic point load （displacement） of the skeleton curve from the freezing-thawing damage members were established with freezing-thawing damage variable D to characterize the damage degree of freezing-thawing damage of concrete. By taking into account the strength and stiffness degradation caused by the cumulative damage effect, a cyclic degradation indexβ1 was introduced, and then the hysteretic rules and restoring force model applied to squat RC shear wall specimens after freezing-thawing cycles were proposed. For verifying the accuracy of the model, four low RC shear walls subjected different freezing-thawing cycles were selected to calculate their hysteretic curves and cumulative hysteretic energy dissipation, which were compared with the experimental data. The results are in good agreement, which means the restoring force model shows a good precision and can provide a theoretical basis for elasto-plastic analysis of shear wall structures in cold regions.