Study On Mechanical Properties And Parametric Analysis Of The Bottom Flange Bolted And Top Flange Welded Diaphragm-through Connection

The research background of this paper is the bottom flange bolted and top flange welded diaphragm-through connection(TWB joint)between rectangular concrete filled tube column and h-shaped steel beam.In response to the call for national assembly development,it is urgent to push forward the structure system of concrete-filled tube column and steel beam.Because it is difficult to weld the bottom flange and diaphragm,the welding quality of the joint whose traditional flange and diaphragm is welded is poor,and the fracture of weld is easy to occur under seismic action,which leads to the structure collapseand.The complete bolted joint has higher cost,higher demand for construction precision and higher field construction difficulty.Therefore,it is proposed that the new connection joint—the bottom flange bolted and top flange welded diaphragm-through connection(the top flange of the steel beam and the top diaphram are welded,the bottom flange and the bottom diaphram are connected with high-strength bolts).Aiming at the performance of the bottom flange bolted and top flange welded diaphragm-through connection,a comprehensive research is carried out in this paper,and the main contents include:(1)In order to verify the reliability and accuracy of a large number of parametric analysis models in this paper,based on the low cycle reversed loading experiments of the three TWB joints and the pure bending tests of four joint specimens with different connection,7 finite element models with the same size and forms are established,which take into account the material nonlinearity,contact nonlinearity and geometric nonlinearity,using ABAQUS finite element software,the finite element results with the experiments of typical failure phenomena?load-displacement curve were analyzed,in order to ensure the correctness and feasibility of the selection of material constitutive,establishment of interaction,mesh generation and setting of boundary conditions in the finite element model.(2)In order to study the seismic performance of the TWB joint,this paper carried out a parametric analysis of the TWB joint.The parameters include the wall thickness of the steel tube column,the number and strength grade of bolts,the thickness and strength of the diaphragm,and the strength of concrete.The results show that the thickness of the steel tube column,the thickness and strength of the diaphragm,and whether the concrete is filled in the steel tube column have a great influence on the bearing capacity,energy dissipation capacity and ductility of the joint.Under the principle of equal strength design,bolts should be selected with high strength grade and few quantity.(3)For the study of the seismic performance under the different connection joints,this paper established the all-bolt connection joint,TWB joint,bolt welding connection joint,all welded connection joint four finite element models,applying low cyclic loading,and compare the hysteresis curves,skeleton curves,bearing capacity stiffness degradation,ductility,energy dissipation and other seismic performance index parameters.At the same time,considering the economy and construction difficulty,it is concluded that the seismic performance of the TWB joint is superior to that of the conventional flange welded joint,and the application of the TWB joint can be vigorously promoted in practical engineering.(4)For the study of TWB joint under the shear performance,this paper established the all-bolt connection joint,TWB joint,bolt welding connection joint,all welded connection joint four finite element models,it is concluded that the core area shear failure form,summarized and put forward the TWB joint's seismic design methods,including "strong column and weak beam" and "strong joint and weak component" method of calculating the flexural capacity and core area shear bearing capacity calculation method,and the correction of strong column coefficient.