Research On Seismic Performance Of Steel-concrete Composite Girder Bridge With Bracing Beam System

The new steel-concrete composite girder bridge with bracing beam system combines the technology of composite beam and precast pier,which can achieve standardized design,industrial production and assembly construction,and thus has a very broad application prospect.As this kind of bridge is less used at present,the seismic damage data are rarely seen,and the research on its seismic performance is not sufficient at home and abroad.At present,there are no relevant seismic design codes and standards that can be followed,which has brought great difficulties to its seismic design.Based on the background of Huaihe River Bridge in ShouXian County,the refined seismic finite element model of precast piers and steel-concrete composite girder bridge with bracing beam system is established respectively,based on this,the structural dynamic characteristics and the seismic response of the new type of composite bridge are systematically studied,and the sensitivity to different design parameters is also studied.Through research,the important characteristics of this kind of bridge in seismic performance and its seismic design method are obtained,which lays a solid theoretical foundation for its popularization and application.The main contents and conclusions of this paper are as follows:Firstly,the fiber model of precast pier is established based on OpenSees platform.The seismic weak points and the design parameters that affect their seismic performance are obtained through pushover and dynamic time history analysis.Secondly,SAP2000 is used to establish the refined,local refinement and bar-resilient finite element model of the whole bridge for the steel-concrete composite girder bridge with bracing beam system,and through the influence of structural dynamic characteristics and seismic response prediction,the applicable scope of different modeling methods was obtained.Then,based on the refined seismic finite element model of the steel-concrete composite girder bridge with bracing beam system,the sensitivity factor of the dynamic characteristics of the whole bridge is analyzed for the relative stiffness ratio of the girder and slab,the shear stiffness of shear studs and the steel beam.The results show that the shear stiffness of shear studs has the greatest influence on the dynamic characteristics of the structure.It not only changes the natural period but also changes the appearance order of the vibration modes and the mass participation coefficient;the stiffness ratio of the slab and the steel beam have little influence on the dynamic characteristics of the structure,only has a certain effect on the high-order vibration mode of the structure.Finally,based on probabilistic seismic demand analysis,the influence laws of the relative stiffness ratio of girder and slab,the shear stiffness of shear studs,steel beams and other design parameters on the dynamic response of the steel-concrete composite girder bridge with bracing beam system were investigated.The results show that the stiffness reduction of shear studs leads to relative slip between the girder and slab,and significantly reduces the seismic response of bearings and piers,while the relative stiffness ratio of the girder and slab and the steel transverse beam have relatively small influence on the seismic response.Comprehensive dynamic characteristics and dynamic response analysis,the shear stiffness of the shear studs is a design factor that needs attention for the anti-seismic of the steel-concrete composite girder bridge with bracing beam system.