Seismic behaviour of combined steel framed-tube substructure with replaceable shear links

Abstract

A combined steel framed-tube structure with replaceable shear links (SFTS-links) can make plasticity isolated to links for rapid replacement of damaged links and improve the applicability of SFTS-links with enhanced ductility in high-seismic zones. In this paper, the seismic performance of thirty-storey SFTS-links and SFTS was compared by elasto-plastic time history and nonlinear static analyses. A 2/3-scale double half-storey, one-bay substructure was tested under cyclic loading in two stages. The substructure was repaired by replacing the damaged link in Stage I. Then the substructure restored to its original position was loaded to destruction in Stage II. Analysis of the substructure was conducted for two stages. The results indicate that ductility of SFTS-links is 34% higher than that of SFTS; the link can be replaced even at the story drift angle of 0.43%; replacing the damaged link can substantially improve the performance of the damaged structure; the ductile factor and the maximum viscous damping ratio of the specimen are 3.92, 0.39, respectively, and the maximum rotation angle and overstrength factor of the link are 0.147 rad, 1.54, respectively; the failure mode of the link is that expansion of the weld crack at the chamfer position of stiffeners causes tearing of link web and fracture of stiffeners. A numerical model is developed and verified with the test results. With increasing link length, initial stiffness, peak strength and cumulative energy dissipation decrease. It is recommended that the length ratio of the link should be 0.93–1.26 in SFTS-links.