Experimental and numerical investigation on strengthening mechanism of rib-reinforced round-over-round RCFDST column jointed with steel beam under cyclic loading

This paper involved both experimental and numerical investigations on the behaviour of twelve types of recycled-concrete filled double-skin steel tubular (RCFDST) structures subjected to the cyclic loading with reinforced ribs at the column–steel beam joints, of which the damage pattern and seismic performance were analysed by varying the ratio of beam–column flexural linear stiffness, axial compression ratio, hollow ratio, type and strength of the concrete, and the length of ribs. The results indicate that the specimens primarily exhibited the damage pattern of the plastic hinge at both ends of the beams, and that the horizontal load–displacement hysteresis curves with full loop at the top of the column were observed. Moreover, the structures composed of recycled concrete from 40 MPa to 60 MPa presented no reduction in ultimate load as well as the joint ductility to those of the ones with normal concrete. Regarding the performance of RCFDST, the optimal ratio of beam–column flexural line stiffness (ki) is found in the range of 1.0 to 1.5. This study demonstrated that the recycled concrete made from the industrialized aggregate formed by crushing waste concrete from road bases has potential application prospects in Concrete-filled double skin steel tubular (CFDST) structures due to its low cost and good seismic performance, including high ultimate load capacity and low energy consumption.