SEISMIC BEHAVIOR OF MOMENT CONNECTIONS FOR CONCRETE-FILLED SQUARE STEEL TUBE EDGE COLUMN

A total of three interior diaphragm connections which have only three of the edges welded to the tubes for concrete filled square steel tube with different axial load ratios had been tested under low-cyclic reversed loading at the end of column to investigate the failure modes, ductility, energy dissipation behavior. The experimental results demonstrated that the vertical force on the side of the interior diaphragm welded to the column flange was about one third of that on the other side. When the displacement of the top of column was approximate 70mm. the local buckling of the beam flanges occurred where the interior diaphragm was welded to the column flanges. The results indicated that all specimens had very good ductility and energy dissipation capacity. The story angle drift ductility ratios are mu=3.40 similar to 3.45, the elastic and elasto-plastic story angular drift are phi(y)=0.0075 similar to 0.0083rad and phi(u)=0.0279 similar to 0.0286rad respectively, and the equivalent viscous damping coefficients are h(e)=0.426 similar to 0.462, which met the requirements of the current code for seismic design of buildings. The interior diaphragm connection, which has only three of the edges welded to the tubes, can be used for edge column connections.