研究目的:近年来,近断层地震对桥梁响应的影响日益引起研究者的注意,现有铁路规范对近断层效应的考虑较少。为研究方向速度脉冲效应对高速铁路桥梁地震响应的影响,基于Pacific Earthquake Engineering Research Center(PEER),Next Generation Attenuation Relationships for Western US(NGA West)强震数据库,采用ANSYS分析软件、ANSYS-APDL语言和弯矩曲率关系计算程序,建立了高速铁路桥梁全桥模型,考虑了轨道不平顺的影响,计算了近/远断层地震作用下桥梁的弹塑性地震响应。研究结论:(1)相比于远断层地震以及非脉冲型地震,方向脉冲型近断层地震对短周期结构地震响应影响较大,会增加桥梁位移及内力响应,其滞回特性表现出荷载-变形曲线中间加强的特点,会增加桥梁的结构和非结构损伤;(2)由于近断层地震较大的竖向地震动会改变桥墩轴力,导致梁体竖向挠度比远断层地震增加较多,《铁路工程抗震设计规范》(GB 50111—2006)等规范规定竖向地震为横向的65%,会低估梁体竖向动力响应;(3)本文研究成果可以为高速铁路桥梁抗震设计提供参考,也为今后相关设计规范、标准的修订提供技术支持。
The vehicle-track-bridge(VTB)element was used to investigate how a high-speed railway bridge reacted when it was subjected to near-fault directivity pulse-like ground motions.Based on the PEER NAG Strong Ground Motion Database,the spatial analysis model of a vehicle-bridge system was developed,the VTB element was derived to simulate the interaction of train and bridge,and the elasto-plastic seismic responses of the bridge were calculated.The calculation results show that girder and pier top displacement,and bending moment of the pier base increase subjected to near-fault directivity pulse-like ground motion compared to far-field earthquakes,and the greater deformation responses in near-fault shaking are associated with fewer reversed cycles of loading.The hysteretic characteristics of the pier subjected to a near-fault directivity pulse-like earthquake should be explicitly expressed as the bending moment-rotation relationship of the pier base,which is characterized by the centrally strengthened hysteretic cycles at some point of the loading time-history curve.The results show that there is an amplification of the vertical deflection in the girder's mid-span owing to the high vertical ground motion.In light of these findings,the effect of the vertical ground motion should be used to adjust the unconservative amplification constant 2/3 of the vertical-to-horizontal peak ground motion ratio in the seismic design of bridge.
