Research On Mechanical Behavior Of Composite Bridge Tower And Steel-concrete Joint Of Hybrid Girder Cable-stayed Bridge

In recent years,steel-concrete composite structures and steel-concrete hybrid structures have been widely used in long-span cable-stayed bridges due to their good mechanical properties.The steel-concrete composite bridge tower has the advantages of both steel bridge towers and concrete bridge towers,and has tremendous application prospects.However,at present,there is little research and application on steel-concrete composite bridge tower in China.As the key part of the design and construction of the hybrid girder cable-stayed bridge,the steel-concrete joint(SCJ)of main girder plays an important role in connecting the steel and concrete girders,and ensuring that the force in steel girders can be transferred to concrete girder smoothly.The load transfer mechanism and mechanical behavior of the SCJ have been investigated by many scholars.However,the composition of the SCJ is complicated and the guidance of previous research is limited.Therefore,adopting a hybrid girder cable-stayed bridge with single pylon located at Dongfeng Road in Siping City,Jilin Province,as an example,the mechanical property of the steel-concrete composite bridge tower and the SCJ of main girder were investigated through model test and numerical simulation.Besides,the calculation method of bearing capacity of steel-concrete composite bridge tower and the force transfer mechanism of the SCJ of the main girder was studied in details.The results could provide a reference for the design and construction of the composite bridge tower and the SCJ.The main research contents and results are given as follows:(1)A 1:8 scaled model of the steel-concrete composite bridge tower segment was fabricated based on principle of similarity,on which an eccentric compression test was carried out.The variation of the strain of steel panels and concrete of the tower with the applied eccentric load were investigated and the bearing capacity and failure modes of the model were obtained.Based on the related specifications and literature on the bearing capacity of concrete-filled steel tubular column,a calculation method for the bearing capacity of steel-concrete composite bridge tower was proposed.(2)Through the axial compression experiment of the steel fiber reinforced self-compacting concrete(SFRSCC),the variation of compressive strength of the SFRSCC with age was studied.The effect of the incorporation of steel fiber on mechanical properties and crack resistance of concrete were discussed.(3)A test model of steel-concrete joint with a ratio of 1:4 was designed and made based on the principle of similarity,and the plan for measurement point arrangement and loading were developed.The mechanical property of the SCJ under the action of the eccentric compressive load and the variation of the main component stress of the SCJ with the applied load were studied.(4)The numerical model of steel-concrete composite bridge tower and the SCJ of the main girder were established by finite element software ANSYS.The mechanical behavior and stress distribution of steel-concrete composite bridge tower section and tower-beam joint were studied.The load transfer mechanism of the SCJ was studied and the effect of the thickness of the bearing plate,the diameter and longitudinal spacing of the shear stud,and the diameter and longitudinal spacing of the perforating rebar on the force transfer of the SCJ was also investigated.