Experimental study on seismic behavior of steel framed tube substructures with a replaceable double-channel Q235 link

Steel framed-tube structures with double-channel web-bolted connected replaceable shear links (SFTS-RSLs) were proposed to resolve the problem of poor ductility and difficult post-earthquake repair of traditional steel framed-tube structures. In order to study the seismic behavior of SFTS-RSLs and replaceability of double-channel links, two 2/3 scale one-bay and double-half-story substructures of SFTS-RSLs with two link lengths (400 mm and 280 mm) were subjected to two-stage pseudo-static tests. The parameters of the nonlinear isotropic/kinematic hardening model were calibrated based on reciprocating tension and compression tests of the link web. The FE models of the substructure specimens were validated based on the stage Ⅱ test results of the specimens, and the influence of the double-channel link length and the reinforcement plate of the link on the rotation capacity of the links were analyzed. The results show that the replaceable maximum story drift angles of double-channel Q235 shear links with lengths of 400 mm and 280 mm are 0.32% and 0.27%, respectively. Their overstrength factors are greater than the value of 1.5 recommended by Popov et al, and their plastic deformation capacity meets the requirements of American standard ANSI/AISC 341-16. Replacing the links can make the performance of the substructure close to the initial level. The ductility coefficient and cumulative energy dissipation of the substructure with the short double-channel link are significantly lower than those with the long double-channel link. The failure modes of the substructures are web tearing failure caused by the expansion of weld crack at the chamfer of the stiffeners of the link. The double-channel link length is recommended to take 0.14-0.23 times the column distance, and the reinforcement plate of the link should be considered at the joints in design.