| Steel-concrete mixed structure adopts two or three forms of steel structure,concrete structure and composite structure in different parts,and the connection of those different parts is realized through the steel-concrete joint segment.Steel is known for its strong tensile strength,while concrete has excellent compressive strength.Steel-concrete mixed structure enables the cooperative work and the full play to the advantages of steel and concrete.This paper focuses on the application of steel-concrete mixed structure in cable-stayed bridge pylons.In this paper,a cable-stayed bridge in Nanjing is taken as the research object,the force status of the cable-stayed bridge under different load cases are studied through spatial rod system theory.The finite element analysis software ABAQUS is used to analyze the local stress of the steel-concrete joint segment at the pier tower joint,taken the internal force of the steel tower under the most adverse load case as the boundary condition.The influence of concrete grade,pressure bearing plate thickness,prestress of anchor rod and other parameters on the stress of the joint segment in tower are taken into consideration for the optimization analysis of the joint segment design parameters.The main research contents of this paper are as follows:Firstly,the finite element analysis double-beam model of a double-tower cable-stayed bridge with the main span 500 m is established through the finite element software MIDAS CIVIL 2019.The finite element model is analyzed under various load cases,and the internal force states of the bottom of bridge tower under various conditions are extracted and summarized,which is prepared for the subsequent research on the steel-concrete joint section.Secondly,the refined finite element model of steel tower-concrete joint segment is established.The finite element model is analyzed under the most adverse working conditions in the normal use stage,and the stress state of each component in the joint segment is studied.Meanwhile,the prestress loss caused by elastic compression of the tower sections would be automatically considered by the finite element software.When calculating the prestress loss,therefore,the iterative method can be adopted to eliminate the prestress loss caused by the dead weight of steel tower and its influence on the stress calculation result of the joint surface so as to avoid the situation that the calculation of prestress loss is too large.Then,the rationality of the boundary conditions of the finite element model is studied.The boundary conditions are simulated as consolidation and spring restraint respectively,and the internal force changes of the joint segment are analyzed.The analysis results show that the stress calculated from the consolidation of the bottom surface of the cap is partial to safety,that is,the simplification of the modeling boundary conditions is reasonable and reliable.Finally,the stress mechanism of the pressure bearing joint section of steel tower and concrete pier is studied,and the influence of the design parameters of the pressure bearing joint segment on local stress is analyzed from three aspects: the concrete strength grade of the cap,the thickness of the pressure bearing steel plate and the initial prestressed tension value of the prestressed bolt. |
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