大跨度连续梁桥弹塑性动力响应分析

Analysis on Elastic⁃Plastic Dynamic Response of Long Span Continuous Girder Bridge

在罕遇地震作用下,桥梁墩柱多数会进入弹塑性阶段。为研究大跨度连续梁桥的弹塑性动力响应规律,首先基于SAP2000软件建立一座大跨度连续梁桥的三维有限元模型,采用墩底集中塑性铰的方法模拟桥梁墩体在地震作用下的塑性行为;其次按JTG/T B02⁃01—2008《公路桥梁抗震设计细则》选择3条实测地震波作为该桥地震动输入;最后对该桥进行非线性动力时程分析。研究表明:相同地震强度下,塑性分析比单纯弹性分析时位移增大,内力减小;塑性分析下桥墩顺桥向及横桥向弯矩均比弹性分析下有所减小,最大减幅为51.21%,最小减幅为26.10%;塑性铰耗能作用明显,顺桥向墩底最大转角位移塑性分析超过弹性分析结果达681.82%。说明塑性分析下桥墩的塑性变形吸收和消耗了部分地震波能量使桥墩内力减小。

Under the rare occurrence earthquake,most of the bridge piers will enter the elastic-plastic stage.In order to study the elastic-plastic dynamic response law of long span continuous girder bridge,firstly,a three-dimensional finite element model of a long span continuous girder bridge was established based on SAP2000 software,and the plastic behavior of bridge pier under earthquake was simulated by the method of concentrated plastic hinge at pier bottom.Secondly,according to JTG/T B02-01—2008 Guidelines for Seismic Design of Highway Bridges,three measured seismic waves were selected as the seismic input of the bridge.Finally,the nonlinear dynamic time history analysis of the bridge was carried out.The results show that under the same seismic intensity,the displacement of plastic analysis is larger than that of simple elastic analysis,and the internal force is smaller.The bending moment along the bridge and across the bridge of pier under plastic analysis is smaller than that under elastic analysis,with the maximum reduction of 51.21%and the minimum reduction of 26.10%.The energy dissipation effect of plastic hinge is obvious,and the maximum rotation displacement along the bridge is 681.82%higher than that of elastic analysis.It shows that the plastic deformation of the pier absorbs and consumes part of the seismic wave energy under the plastic analysis,which reduces the internal force of the pier.