无黏结预应力RC桥墩抗震性能的数值分析

Numerical analysis of the seismic performance of unbonded prestressed RC bridge piers

配置竖向无黏结预应力筋,利用其弹性恢复力减小钢筋混凝土桥墩在大震下的残余位移和裂缝宽度,是实现桥墩地震损伤控制的有效手段。本文在完成的拟静力试验基础上,基于OpenSees分析平台建立了无黏结预应力钢筋混凝土桥墩抗震数值分析模型,采用非线性纤维梁柱单元模拟桥墩的弯曲变形,采用修正的压力场理论计算试件剪切变形并通过剪切弹簧模拟,通过零长度转动弹簧模拟纵筋拔出变形,三者共同考虑试件在地震下的弯-剪-轴力耦合作用。将模拟得到的试件滞回曲线、残余位移、预应力筋应力等与试验结果进行了对比,同时将模拟得到的墩顶弯曲变形、纵筋拔出变形和剪切变形进行了分离。结果表明:模拟得到的试件滞回曲线、残余位移、预应力筋应力等与试验结果吻合良好,该模型可对竖向配置无黏结预应力筋钢筋混凝土桥墩的抗震性能进行准确的模拟分析。纵筋拔出变形可占墩顶总变形的30%~50%,在数值模型中不可忽略。

For seismic damage prevention design of reinforced concrete(RC) bridge piers,longitudinal unbonded prestressed tendons were used to minimize residual displacement and concrete cracking width of the piers under seismic action.Based on quasi-static test results,a numerical model for seismic analysis of the unbonded prestressed RC bridge piers was built on the basis of OpenSees analysis platform.In this model the nonlinear fiber beam column element was used to simulate the flexural deformation of the piers.The shear deformation was calculated by the Modified Compression Field Theory(MCFT) and simulated by the shear spring element.While the longitudinal bar slip deformation was modeled by the zero length rotation spring.Thus,flexure-shear-axial interaction of the piers under seismic action was simulated by combining the three deformation components.The simulated hysteretic curves,the residual displacement,and the unbonded prestressing tendon stress were compared with experimental results.Also,the flexural,shear and longitudinal bar slip deformations of the piers obtained by the numerical model were obtained.The results indicate that simulated hysteretic curve,residual displacement and unbonded prestressed tendon stress agreed well with test data.And the model could be used to simulate the seismic behavior ofthe longitudinal unbonded prestressed RC bridge piers.The longitudinal bar slip deformation would account for30% ~ 50% of the total lateral displacement,and should not be neglected in the analysis model.