Experimental and numerical study on seismic performance plate-reinforced and tapered-reduced composite joints

Abstract High-strength steel welded connection is characterized by large stiffness, insufficient rotation capacity of joints, and limited plastic deformability. Moreover, brittle failure will easily occur in joint welds during a strong earthquake. The improvement idea—“transition through plate connection” and “reduction of beam flange into a tapered shape (tapered reduction)”—for a beam flange can effectively enlarge the range of yield zone and protect beam-end welds from brittle failure while improving the deformability and energy-dissipating capacity of joints. This study performed a low-cyclic loading test of five Q690 high-strength steel plate-reinforced and tapered-reduced composite joints. Their seismic performance indexes, such as bearing capacity, hysteretic behavior, stiffness, and ductility, were analyzed. The influencing laws of the different parameters on performances were discussed as well. Results indicated that the plastic energy consumption of composite joints was mainly concentrated in the tapered reduction zone, which could synchronously enter the plastic phase, thereby expanding the plastic yield area on the flange while realizing the outward shift of the plastic hinge and possibly improving the energy-dissipating capacity of the joints. When the reduced sectional width d increased by 40%, the ultimate bearing capacity of the joints was elevated by 20.63%, while the ductility coefficient was reduced by 10.69%. The ductility coefficient should be reduced by 10.69%, and reduced depth and length should be (0.6–0.7) bf and (0.6–0.95) hb, respectively.