Experimental studies on seismic behavior of connection for concrete-filled square steel tube edge column

A total of three interior diaphragm connections with only three edges welded to the tubes for concrete-filled square steel tube with different axial compression force ratios have been tested under low-cyclic reversed loading at the end of column to study the failure modes,ductility,and energy dissipation behavior.The experimental results demonstrated that the vertical force on the side of the interior diaphragm which was not welded to the column flange was about one third of that on the other side where the interior diaphragm was welded.The welds between column walls around beam flanges on the side,where the interior diaphragm was not welded to the column flanges,cracked.When the displacement of the column top was approximately 70mm,the local buckling of the beam flanges occurred at the side where the interior diaphragm was welded to the column flanges.The study results indicate that all specimens have very good ductility and energy dissipation capacity.The story angle drift ductility ratios are μ=3.40~3.45, the elastic and elasto-plastic story angular drift are φy=0.0075~0.0083rad and φu=0.0279~0.0286rad respectively,and the equivalent viscous damping coefficients are he=0.247~0.462,which meet the requirements of the current code for seismic design of buildings.The interior diaphragm connection with only three edges welded to the tubes can be applied in edge column connections.