某城市轨道交通连续梁桥延性抗震设计

Seismic Ductility Design of Continuous Beam for Urban Rail Transit

城市轨道交通桥梁结构在跨越现状及规划路时一般采用预应力混凝土连续梁型式,作为重点设防类结构,抗震分析是桥梁结构设计中重要且较为控制的一环。以某城市轨道交通(30+50+30)m预应力混凝土连续梁为例,采用Midas/Civil分析软件建立分布式纤维铰有限元模型,进行罕遇地震下弹塑性时程分析。结果显示:除P3号活动墩在地震波纵向作用以及P2号固定墩在地震波1横向作用下未达到屈服之外,其余桥墩墩底塑性铰截面均达到屈服,进入塑性状态。通过检算,各墩底塑性铰截面纵横向抗剪能力和变形能力等延性指标满足《城市轨道交通结构抗震设计规范》要求,并结合变形验算结果确定结构性能等级,判断该连续梁桥符合重点设防类结构要求。

Prestressed concrete continuous girder bridge is generally used in urban rail transit bridges when crossing the existing and planned roads.As a key fortification structure,seismic analysis is an important and controlled factor in bridge structure design.Research on elastic-plastic time-history analysis of a prestressed concrete continuous girder bridge(30+50+30)m from urban rail transit under rare earthquakes was carried out based on finite element analysis model of distributed fiber hinge built by Midas/Civil software.The results showed that,the P3 active pier and P2 stable fixed pier were not yielded under the longitudinal and latitudinal seismic force from seismic wave 1,respectively.Except that,the other piers yielded and went into plastic state.Furthermore,the ductility indicators,such as the vertical and horizontal shear resistance,deformation capacity of the piers,meet the requirements of the"Code for Seismic Design of Urban Rail Transit Structures".Combined with the result of the deformation,the structural performance levels determined,and it is estimated that the continuous girder bridge meets the requirements of key fortification structures.