The Nonlinear Finite Element Analysis On T-stub Connection For Concrete-filled Square Steel Tubular Column To Steel Beam

As a new type of joint connection, concrete-filled steel tubular column-H sectionsteel beam connected with T steel is proposed by some researchers in recent years.However, there is only very limited research about its seismic performance andapplication all over the world. This connection is constructed by welding the upperand lower flange of beam separately with T section steel web plate and connecting Tsteel on both sides of the column with square steel tube concrete column through highstrength bolts. Based on summarizing the traditional steel and concrete compositejoints, the mechanical performance of the joint of this new type under cyclic loadingsis addressed by nonlinear finite element simulation and mechanical model formulationin this thesis. The main points of the thesis are as follows:(1)A state-of-the-art literature review of semi-rigid connection research isprovided in this thesis, including semi-rigid joint classification and various forms ofresearch status etc. In order to formulate mechanical model for the joint of this type,the existing moment-rotation curves proposed by researchers are also summarized.And an introduction to finite element analysis is provided in this thesis, where thechoice of material constitutive relation and finite element model establishmentmethod are discussed in details. The initial imperfection is introduced in the finiteelement simulation to consider the component initial defects.(2)The finite element model of the T-stub connection for concrete-filled steelsquare tubular column and steel beam is established in the general finite elementsoftware ABAQUS, where material, geometric and contact nonlinearity are modeled.The load-displacement hysteresis curve, the moment-angle hysteresis curve, the stressdistribution of concrete-filled steel tube column, the T section steel flange of contactstress and high strength bolts stress distribution are obtained through applying lowreversed cyclic loading to the beam end. In model validation, the simulation resultsare in good agreement with experimental results. It shows that the proposed finiteelement model is feasible to simulate the joint.(3)The mechanical response of the joint under antisymmetric monotonic loadingis simulated by ABAQUS. Compared with the repeated load simulation results, theyare in good agreement in the elastic stage, while there is large difference between the load-displacement curve in the yield stage. It turned out that it is not suitable to studyseismic performance of the joint of this type with monotonic loadings.(4)A comprehensive parametric study of T-stub connection joint forconcrete-filled steel square tubular column and steel beam is conducted,including theratio of axial compression,T steel flange thickness and high strength bolt diameter etc.The influence of each parameters on the joint’s mechanical performance is deeplyanalyzed.The calculation method of the bearing capacity of each component isformulated.Based on the requirement of specification and experience,the layoutrequirements of the weld structure for the joint and bolt are summarized.