Experimental investigation and analytical modeling of steel beam-to-CFDST column connection

Abstract

In this paper, a prefabricated connection between concrete-filled double-skin steel tubular (CFDST) column and steel beam with flush endplates and bidirectional bolts was developed. To investigate the effects of the endplate thickness, axial compression ratio, bolt diameter, concrete fill degree, and shape of the inner tube on the seismic performance of the connection, a series of pseudo-static tests were performed on six specimens. It was observed that the bending deformation of endplates, warpage of bolts, local buckling of beam flanges, and cracking of weld seams were typical failure modes. An increase in the endplate thickness and the replacement of the circular inner tube by the square inner tube significantly improved the ultimate strength of the connection. The ultimate strength of the connection was not sensitive to the axial compression ratio and bolt diameter, and it decreased as the concrete fill degree increased. The displacement ductility coefficients of the specimens were greater than 6.21. Higher ductility and accumulated energy dissipation were obtained by increasing the endplate thickness, axial compression ratio, bolt diameter, and replacing the circular inner tube with the square inner tube. The ductility and accumulated energy dissipation decreased as the concrete fill degree increased. Based on the component method, an analytical model of the initial rotational stiffness of the connection was developed. The mean and standard deviation of the ratios of predicted values to test values were 0.95 and 0.06, respectively.