城际铁路变宽度连续箱梁桥的动力特性

Dynamic Characteristics of the Inter-city Railway Variable Width Continuous Box Girder Bridge

研究了变宽度连续箱梁桥在成桥状态下的动力特性.以某五跨变宽度连续箱梁桥为背景,建立整桥三维空间有限元模型,对大桥的模态进行分析,并选用50年超越概率分别为3%(E1)和10%(E2)两个水准的反应谱进行成桥阶段的地震响应分析.结果表明:E1,E2概率下,变宽度连续箱梁桥制动墩上的内力较大,且顺桥向地震荷载作用对制动墩的内力影响比横桥向地震荷载作用大,竖向地震荷载作用对桥墩轴力影响较大,而对桥梁上部结构位移影响不大,变宽度连续箱梁桥地震反应随桥墩高度增加而增强.建议桥梁设计时,重点考虑固定墩及固定支座的设计,并对固定墩底部进行加固处理,抗震分析时,慎重考虑地震荷载竖向分量取值.通过地震反应谱分析,在规范要求的地震荷载作用下,变宽度连续箱梁桥整体抗震性能良好,满足抗震设计要求.

Dynamic characteristics of a variable-width continuous box girder bridge under completion state were studied.Based on a five-span continuous box bridge with variable width of the inter-city railway between Zhengzhou and Xinzheng international airport,the model was established through finite element method and modal analysis was carried out.The space beam element model was used to simplify the calculation,focusing on the simulation of boundary conditions,stiffness and mass of the variable width continuous box girder bridge.In the seismic response analysis,stiffness in vertical and three rotational directions can simply hand because the response of the bearing horizontal stiffness was large to the earthquake.Main beams and piers used space beam element and bearing used spring element to simulate.Between the roof and floor of the main beam,rigid connection was used to simulate.Reference to the arrangement of prestressed steel beam,considering the actual situation of the beam,the whole bridge was separated by the way of finite element.Secondary dead loads including bridge deck pavement,railings,pipelines,etc were into quality.Piers were scattered as a beam element every 1 meter height direction to make the simulation of structure quality distribution more accurate which can improve the calculation accuracy.The whole bridge was divided into 709 nodes and 245 beam elements.Two levels of response spectrum that the exceeding probabilities were respectively 3% and 10% in 50 years were selected to analyze seismic response under finished state.Internal force and displacement were mainly calculated.The results show that the internal force on fixed pier is bigger than other piers＇under the two exceeding probabilities.Earthquake loads along the bridge have more effect on internal force of fixed pier than earthquake loads cross the bridge.The vertical seismic load has a greater influence on the axial force generating in piers while it has a little effect on the displacement of superstructure of bridge.Seismic response is stronger when pier is higher.Earthquake load along the bridge mainly generates the displacement andshear force along the bridge,axial force,in-plane bending moment.Earthquake load cross the bridge mainly produces displacement and pier shearing force cross the bridge,out-plane bending moment.It is suggested that the design of fixed pier and fixed support should be mainly considered in bridge design and vertical seismic load values require serious consideration in seismic analysis.The bottom of the pier should be reinforced.Through the analysis of seismic response spectrum,the overall seismic performance of variable width continuous box girder bridge is good under earthquake loads in specification requirement which also meet requirements of seismic design.