Experimental and numerical investigation of H-beam to recycled aggregate concrete column edge connections under cyclic loading

This paper aims to investigate the cyclic performance of the connections between the recycled aggregate concrete (RAC) column and steel H-beam. In this connection system, the steel beam is welded to the end plate as an integral unit and bolted to the column. The seismic performance differences between the novel casing-type one-side bolted end-plate connection and the conventional all-welded joint with external diaphragm and top-seat angle connection were examined. Subsequently, three types of joints with different connection details were designed and fabricated at a reduced scale of 1:2, following the principle of strong columns and weak beams. Through beam-end loading, the low-cyclic lateral loading test was performed to observe the loading process and failure morphology of the joint model. The load-beam end displacement hysteresis curve and the skeleton curve were obtained to analyze the joint load eigenvalues, ductility, energy dissipation, and stiffness degradation. The experimental results showed that the initial stiffness and peak strength of the casing-type one-side bolted end-plate connection were between that of the all-welded joint with external diaphragm and top-seat angle connection. All three specimens exhibited beam-end failure, with saturated load-displacement hysteresis curves. The displacement ductility coefficients were in the range of 2.66-2.88, and the ultimate elastic-plastic drift ratio was about 5.9-6.2%. Furthermore, a finite element model was established. The effects of axial compression ratio (n = 0.2-0.8), steel tube width-to-thickness ratio (B/ts = 35.7-83.3), outer tube (tw = 3-7 mm), and end-plate thickness (td = 10-20 mm) on the bearing performance of the outer tube one-side bolted end-plate joint under lateral loading were analyzed. It was demonstrated that the load-carrying capacity of the specimen was significantly affected by the thickness of the outer tube and end-plate thickness, while the effect of the variation of the axial load level was small.