EFFECT OF STRENGTH OF FILLED-CONCRETE ON STRUCTURAL PERFORMANCE OF CONTINUOUS BEAM-TYPE SQUARE CFST BEAM-TO-COLUMN CONNECTION

Continuous beam-type concrete-filled steel tube (CFST) column connections are simple to fabricate and exhibit effective seismic performance. Fujinaga and Clifton have previously studied the performance of continuous beam-type square CFST beam-to-column connections using concrete of relatively high strength (85 MPa) and demonstrated their effective performance and high energy-absorbing capacity. However, in their study, it was found that the local deformation of the steel beam under bending-induced beam tension had a large effect on the steel tube flange near the connection. Further, it was observed that filled concrete may not contribute substantially to the transmission of compressive load at the connection panel if low-strength concrete is used. In this study, the square CFST beam-to-column connection was investigated, and the connection performance and load transfer mechanisms were examined when the strength of the concrete was relatively low (40 MPa). The specimens demonstrated effective seismic performance, exhibiting sufficient strength and stable hysteretic behavior with high energy absorption even when low-strength concrete was used. Irrespective of the strength of the concrete used, the strain developed in the steel tube flanges was low on the compression side, and the filled concrete contributed to the transmission of the compressive load at the connection panel. The compressive strain in the steel tube was slightly higher when the strength of the concrete was low.