In order to solve the problem of large space occupation, long time to build and high fee for the single line bridge, we establish finite element model of single and double prestressed concrete rails bridges to study space vibration response under the rail traffic loads. Establish vehicle subsystem model and bridge subsystem model, ignore track vertical irregularities, consider the vehicle transverse serpents in using IMDplus for dynamic calculation under the mobile load. It is concluded that the main frequency to achieve resonance can increase 12% for double rail line to single rail line;In the load case of when single rail line passed,the displacement of transvers and vertical respectively decreases 42% and 36% for double rail line bridge to single rail line bridge,its acceleration for the transvers and vertical also respectively decreases 21% and 22% , In the load case of when double rail line passed, the displacement and acceleration of transvers and vertical also respectively decreases 20%,17%,12% and 17%. It can get that the double line bridge saves more space, has bigger stiffness and smaller structure dynamic response than those of single.%目的 为解决一体式单线桥梁占地空间大、施工周期长、造价高的问题,建立单双箱有限元模型,对单双线高架桥梁在轨道荷载的动力作用下进行研究.方法 分别建立桥梁子系统模型和车辆子系统模型,忽略轨道竖向不平顺,考虑车辆横向蛇形运动,运用快速模态动力学分析工具(IMDplus)进行移动荷载作用下桥梁结构动力响应计算.结果 双线桥的主频率比单线桥大12％；单列车过桥工况下,双线桥的横、竖向位移比单线桥分别减少42％、36％,双线桥的横、竖向加速度比单线桥分别减少21％、22％；双列车过桥工况下,双线桥的横、竖向位移及其加速度较单线桥分别减少20％、17％和12％、17％.结论 在轨道交通荷载作用下双线桥较单线桥具有刚度大、节省空间、结构动力响应小等优势.
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