弯曲破坏型钢筋混凝土桥墩地震变形成分及影响因素

Seismic Deformation Components and Influential Factors of RC Bridge Columns Suffering from Flexural Failure

钢筋混凝土桥墩拟静力试验表明,弯曲破坏型桥墩墩顶位移主要由弯曲变形、滑移变形成分构成。为进一步探讨地震荷载作用下弯曲破坏型桥墩地震变形成分及其影响因素,首先基于Lehman以及李贵乾的桥墩试件拟静力试验,利用OpenSees平台采用纤维梁柱单元模型附加零长度截面单元对试验滞回曲线和墩顶变形成分进行数值模拟;其次建立原型桥墩数值模型,考虑近断层和远断层地震动进行了非线性动力时程分析,探讨了最大侧移角、位移延性系数等结构反应参数,以及剪跨比、纵筋配筋率等构件特征参数对桥墩地震变形成分的影响。结果表明,墩顶总位移中纵筋粘结滑移成分随最大侧移角和位移延性的增大而增大,随剪跨比和纵筋配筋率的增大而减小。考虑纵筋粘结滑移的数值模型与仅考虑弯曲变形纤维梁柱单元模型相比,将增大桥墩的地震位移反应。

The related quasi-static tests verify that the top lateral displacements of RC bridge columns suffering from flexural failure consist of bending deformation and bar bond slip deformation（bar pulling out deformation）.To further investigate the deformation components under earthquake loading and their influential factors,Lehman and LI Guiqian′s test results are simulated for hysteretic curves and deformation components on the platform of OpenSees,with the model of fiber beam-column element adding zero-length section element.Then the prototype models are built for nonlinear dynamic analysis,considering near-fault ground motions and far-fault ground motions.Parameters of structural response（the maximum lateral drift ratio and displacement ductility factor）and structural characteristics（the aspect ratio and longitudinal reinforcement ratio）are taken as influential factors.The results show that the bar bond slip deformation component in total lateral displacement increases with the growing of the maximum lateral drift ratio and displacement ductility factor,and decreases with the increasing of the aspect ratio and longitudinal reinforcement ratio.In addition,the numerical models considering the bar bond slip will magnify the seismic responses of RC bridge columns by comparison with that ignoring the bar bond slip.