Research On Cooperative Working Mechanism Of Decorative Steel Structure And Rc Girder Of Urban Landscape Bridge

Urban landscape bridges usually use girder or slab structures as the basic bearing system to resist the main load of the bridge,and at the same time decorative structures such as arches and cable-stayed systems are arranged for aesthetic purpose.Due to the characteristics of light-weight and easy-processing,steel is often used as decorative systems in practice with obvious specialization and diversification.When subjected to external loads,the decorative structures cannot be completely independent and interact with the girder.Thus,the stress analysis of the bridge during construction process and operation of the bridge is complicated.And the current research on urban landscape bridges focuses on the stress analysis of the decorative structure,rather than the full bridge analysis,so the interaction between the decorative structure and the girder is still unclear.In this paper,taking Jianfeng Bridge and Songhua Bridge as the engineering research background,the cooperative working mechanism of decorative steel structure and RC girder is studied.The Jianfeng Bridge is a three-span RC girder bridge with an additional steel arch decoration structure,and the Songhua Bridge is a two-span RC girder bridge with an additional cable-stayed decorative structure.The main research contents are listed as followed:(1)The Midas/Civil software is used to establish the full bridge finite element model,and the mechanical properties of the bridge structure under different working conditions are calculated and analyzed,including the internal force,deformation and interaction of each part of the bridge.The results show that although the decorative structure does not resist any load for design,it will indeed interact with girder during the bridge operation and have a great impact on the decorative structure.Then,refined finite element model of decorative structure is established using ABAQUS software to analyze type ? stability.Considering the initial eccentricity of the steel structure,the stable bearing capacity of the decorative structure is calculated and analyzed.(2)For the suspender(stay cable),the effect of tension sequences on cable force of suspender(stay cable)is studied under three different tensioning conditions.The results show that the cable force is different with the design value in those former tensioned stay cables and the cable force of latter tensioned stay cables is close to the design value.During the tensioning process,the subsequent tensioned suspender(stay cable)will unload the front.When the decorative structure and the girder are stable in deformation,the internal force of suspender(stay cable)will redistribute.(3)Considering the effect of pile-soil effect,the natural vibration characteristics of the bridges according to the multiple Ritz vector method are determined.And the seismic responses of the two bridges are analyzed using the response spectrum method and the time history analysis method,respectively.The results show that,unlike the seismic response of ordinary arch bridges and cable-stayed bridges,the maximum internal force of Jianfeng Bridge and Songhua Bridge under earthquake does not appear at the bottom of the arch or tower,but at the girder.In addition,the results obtained using response spectrum analysis and time history analysis are basically the same.(4)The connection nodes with large local stress and detailed structures of the bridges are determined,including anchorage zone of suspender(stay cable),steel arch(tower)foot and other areas.Then,ABAQUS is used to establish refined finite element models to study the force transmission mechanism and stress distribution rules of key nodes and detailed structures,and to determine the stress characteristics of the local area for the steel arch(tower).