Study On The Seismic Performance Of Circular Tubed Column To Steel Beam Connections

Although tubed column to steel beam frame system is one of effective structural systems,the tubed column to steel beam connections have been paid little attention.Thus,the circular tubed column to steel beam connections have been proposed and investigated by methods of experimental study,finite element simulation,and theoretical analysis in this thesis.The objectives of this thesis are summarized as follows:(1)The details of circular tubed column to steel beam connections have been put forward and eight connections were tested under monotonic loading to investigate the failure mode and the shear transfer behavior of the interface between the circular tubed column and the steel beam.Analyses have been carried on the failure modes,the load-displacement relationships and the stresses and strains of joint tube.The finite element model has been established using ABAQUS and the effects of concrete strength,thickness of joint tube,thickness of diaphragm,and width of embedded diaphragm on the shear transfer behavior have been evaluated by parametric analysis.The theoretical formula for the shear transfer capacity was proposed based on effective width method and the requirements for joint details were advised.(2)Six circular tubed RC column to steel beam connections were tested under seismic load.The experimental parameters include thickness of joint tube,extended length of joint tube,and loading mode.Based on experimental results,the failure modes,load-displacement relationships,and stresses and strains of joint tube were investigated.The indexes for ductility,degradtaion of strength,degradtaion of rigidity,and energy dissipation were calculated.(3)Four circular tubed SRC column to steel beam connections were tested under seismic load.The experimental parameters include thickness of joint tube,extended length of joint tube,and axial load ratio of column.Based on the experimental results,the failure modes,load-displacement relationships,and stresses and strains of joint tube were investigated.The indexes for ductility,degradtaion of strength,degradtaion of rigidity and energy dissipation were calculated.(4)The concrete models of existed finite element software were evaluated by theoretical mechanism in the terms of simulating the behavior of concrete under shear-compression loading.The finite element model was establised using MSC.Marc.Parametric analysis was conducted to investigate the influence of core concrete,joint tube,web of shaped steel column,axial load ratio,longitudinal reinforcement,and height to diameter ratio on the seismic performance of proposed connections.(5)Based on the theories of diagonal strut and superposition,the shear-resisting mechanical model and shear-resisting capacity for connections were proposed.Taking equilibrium of force,compatibility of deformation,and material constitutive model into consideration,the shear load versus shear deformation skeleton curves of connections were obtained based on the proposed mechanical model.