焊接环式箍筋约束高强混凝土柱恢复力模型试验研究

对6个1/2比例焊接环式箍筋约束高强混凝土柱进行了低周反复加载试验，研究了轴压比和配箍率对柱变形性能和滞回特征的影响。通过试验结果的回归分析，以位移比、轴压比和配箍率等为主要参数，建立了卸载刚度和反复加载下的承载力退化率的计算式。在试验研究基础上，对滞回曲线特征进行了分析，并根据试验 P-Δ滞回曲线的特征，得到了柱恢复力模型。研究结果表明：采用由弹性、强化和承载力退化三阶段所组成的三折线型骨架曲线，可以反映焊接环式箍筋约束高强混凝土柱的恢复力特性，该骨架曲线按试验实测数据统计回归分析法以及截面条带分析法确定，其强化段和承载力退化段均考虑了轴压比和配箍率的影响。在试验研究基础上，建立了焊接环式箍筋约束高强混凝土柱剪力-侧移恢复力模型。分析和试验结果表明：所建立的恢复力模型能较好地反映不同轴压比与配箍率对柱的滞回规律特性的影响,可用于该类柱的抗震性能分析。

Experimental study on restoring force model of high strength concrete columns confined by butt-welded closed composite stirrups

Six specimens of high strength concrete columns confined by butt-welded closed composite stirrups of 1/2 scale were tested under cyclic lateral loads. The influences of axial compression ratio and volume-stirrup ratio on deformation performance and hysteretic characteristics of the columns were considered in the test. Based on regression analysis of test results, formulae of unloading rigidity and strength degradation rate under cyclic loading conditions were established considering the parameters such as displacement ratio, axial compression ratio and volume-stirrup ratio. Based on the test results, characteristics of hysteretic curves were analyzed, and by analyzing the characteristics of the P-Δ hysteretic loops, hysteretic rule of restoring force model was determined. The research result shows that tri-linear skeleton curve which consists of elastic stage, strengthening stage and strength degradation stage can reflect restoring force characteristics of high strength concrete columns confined by butt-welded closed composite stirrups. Skeleton curves are determined by section layer method and statistical regression analysis method according to test data, and the influences of axial compression ratio and volume-stirrup ratio are all considered in its strengthening stage and strength degradation stage. Based on the research work above, shear force-lateral displacement restoring force model of high strength concrete columns confined by butt-welded closed composite stirrups was established. Analysis and test results show that the restoring force model can well reflect the influences of axial compression ratio and volume-stirrup ratio on the hysteretic rule characteristics of the columns, thus it can be used for the seismic performance analysis of the columns.