双柱墩地震反应的轴力刚度耦合作用

地震作用下钢筋混凝土双柱桥墩产生的动轴力不仅会改变桥墩的屈服强度,而且也会相应地改变桥墩的刚度,但目前广泛使用的集中塑性模型一般并未考虑这种轴力-刚度的耦合作用。以自动计入轴力-强度及轴力-刚度耦合作用的纤维模型分析结果为基准,研究了轴力-刚度耦合作用对钢筋混凝土双柱桥墩地震反应的影响。结果表明,轴力-刚度耦合作用对双柱墩弹性阶段的反应有较大影响,但不改变结构的极限承载力;由于拉压桥墩的刚度互为消长,等高双柱墩的地震位移响应在不计轴力-刚度的耦合作用时与实际情况只略有差异,但墩柱弹性内力响应则会被较大地低估;不等高双柱墩的刚度受较矮侧桥墩控制,因此轴力-刚度的耦合作用对结构的地震位移响应和弹性内力响应都有明显影响,桥梁不规则性越大影响越显著,在进行结构分析时不能忽视这一因素的影响。

Axial Force Stiffness Interaction in Seismic Analysis of RC Double Column Bridges

Earthquake induced dynamic axial force in reinforced concrete（RC） bridge bent columns will not only change the yield strength of the columns but also change their stiffness,which is seldom considered by the common lumped-plasticity line model.Based on the fiber element model results that taking into account the influence of dynamic axial force on strength and stiffness simultaneously,the axial force-stiffness interaction effect on the seismic responses of RC double-column bridges was analyzed.The results show that,axial force-stiffness interaction has a large effect on the seismic responses of the double-column bridge in the elastic range,and it does not alter the ultimate capacity of the columns.Since the stiffness of the columns under compression and tension dynamic axial forces offset each other,the global displacement of bridge bent with equal columns is relatively unaffected by the axial force-stiffness interaction,however,the differences of the column member forces are manifest.For the short column controls the global stiffness,the axial force-stiffness interaction has significant influences on both the global displacement and member force responses.The influences become larger as the irregularity of the bridge bent increases,so the interaction between axial force and member stiffness should be sufficiently considered in seismic analyses.