Seismic tests and nonlinear model of beam-CFDST column joints with blind fasteners

Abstract

In recent years, substantial research efforts have turned towards concrete filled double skin steel tubular (CFDST) column due to its superior mechanical performance. However, an effective and convenient connection method between a CFDST column and a beam still needs to be investigated in depth. This paper tried to adopt the blind bolting technology in a CFDST column to beam connection. A series of joint specimens were prefabricated and designed with different end plate types, column hollow ratios and beam types to carry out pseudo-dynamic tests. Excellent seismic performance was detected for all test specimens. It was observed that increasing the column hollow ratio could moderately increase the ultimate strength and the specimen with extended end plate had higher ultimate strength stiffness compared with that with flush end plate. To accurately capture the dynamic response for this type of joint, an analytical model was developed considering the shear performance of panel zone and moment-rotation behavior of connection. Shear strength of CFDST column panel zone was modified from that of CFST column panel zone based on the yield line method for including the contribution of confined compression strut. It indicated that two potential yield mechanism might appear depending on the column hollow ration (χ). The analytical model could well predict the test results. The research and analytical results provided an effective connection method to assemble a CFDST column to a beam and supply a feasible analytical model to predict the joint performance.