The special-shaped concrete-filled steel tubular(CFST)column structure conforms to the requirements of the modern residential environment for the building structure in terms of building use functions,and has good mechanical and construction performance.At present,the H-shaped steel beam is the most connected to the concrete-filled steel tube special-shaped column,but the overall cost of the H-shaped steel beam is obviously higher and the stability problem of the steel beam under negative bending moment is prominent.As a new type of composite beam,U-shaped steel-concrete composite beam has the advantages of low cost,high rigidity and bearing capacity,less welding workload,good stability,and good fire resistance compared with traditional composite beams.The frame joint between the special-shaped CFST column and U-shaped steel-concrete composite beam is a new type of beam-to-column joint form with reasonable force and suitable for assembly buildings.Therefore,this paper studies the seismic behaviour of the special-shaped CFST column to U-shaped steel-concrete composite beam joint.The specific research work is as follows:A pseudo-static test study on the seismic behaviour of the special-shaped CFST column to U-shaped steel-concrete composite beam joint was carried out.The test parameters include the beam-to-column flexural capacity ratio,the size of the vertical rib connection and the joint detail.The failure mode and load-displacement curve of the specimen were obtained through experiments,and the ductility and energy dissipation capacity,performance degradation,joint stiffness,stress distribution,and beam end displacement composition of the specimen were analyzed.Experimental research shows that the loaddeformation relationship curve of the vertical rib joint is relatively plump,and the seismic performance is good.A refined finite element model of the frame joint between the special-shaped CFST column and U-shaped steel-concrete composite beam was established.The model can accurately predict the load-displacement skeleton curve and the failure mode of key parts.Through finite element analysis,the main stress distribution and force transmission mechanism of the joint specimens are clarified.Based on the parametric analysis,the influence of column axial compression ratio,column steel tube width-to-thickness ratio,U-shaped beam steel plate thickness,longitudinal reinforcement diameter,floor width and vertical rib connection size on the seismic performance of joints is systematically analyzed.A simplified mechanical model of the vertical rib joint is proposed and the calculation formula for the bending bearing capacity of the connection is put forward.The influence of the width-thickness ratio of the column steel tube,the height of the vertical rib,the thickness of the vertical rib and the connection length between the vertical rib and the beam flange on the joint stiffness is analyzed through the finite element analysis.Lastly,the rigid joint design suggestion for the vertical rib connection is given and the design method of the vertical rib joint is improved. |