地基柔性效应对铁路连续梁桥弹塑性地震反应的影响

Influence of Subsoil Flexibility on Elastic-Plastic Seismic Response of a Railway Continuous Girder Bridge

以某高速铁路大跨连续梁桥固定墩纵桥向的弹塑性地震反应为研究对象,建立考虑地基柔性约束效应的单墩动力计算模型,分析地基柔性效应对桥墩动力特性及弹塑性地震反应的影响规律。结果表明:地基比例系数m值的改变对桥墩的1阶自振频率影响较明显;随着地基比例系数m值的降低,墩顶位移及基底位移逐渐增加;地基越软,桥墩的弹塑性地震反应有增大的趋势。为了更加合理的描述桥墩的塑性状态,建议对软土场地桩基础钢筋混凝土桥墩进行延性抗震设计时,优选墩底曲率延性指标进行评价。

This study took the fixed pier of a long-span continuous girder bridge on high-speed railway as the research object, in order to ascertain the fixed pier＇s elastic-plastic seismic response in bridge＇s longitudinal direction. Thus, a dynamic calculation model of single pier considering the subsoil flexibility effect was established, and the influence on the bridge pier＇s dynamic characteristic and elastic-plastic seismic response caused by subsoil flexibility was researched. The results show ： the change of the subsoil scale factor m has obvious influence on the first-order natural frequency of vibration; the pier top and foundation bottom displacements will increase gradually as the subsoil scale factor m decreases; the softer the subsoil is, the bigger the elastic-plastic seismic response of the bridge pier will be. Therefore, it is suggested in this study that the curvature ductility index of bridge pier bottom should has the first priority to be chosen when carrying out the seismic ductility design for reinforced concrete bridge pier with pile foundation in soft subsoil site, so as to reflect the plastic state of bridge pier more reasonably.