Full-Scale Experimental Testing and Postfracture Simulations of Cast-Steel Yielding Connectors

Abstract

The cast-steel yielding connector (YC) is a yielding fuse device designed to dissipate earthquake energy through inelastic deformations in specially designed distributed yielding regions, while ensuring primarily elastic behavior elsewhere in the structure. The YC exhibits a stable, symmetric hysteretic response with a characteristic postyield stiffness increase due to a combination of friction and second-order geometric effects. The ultimate limit state of the YC is governed by the ultralow-cycle fatigue (ULCF) fracture of the yielding sections, where fracture begins after a relatively low number of large inelastic cycles, followed by a slow strength degradation. This paper presents tests and finite-element analyses of small-scale coupons and full-scale tests of a variety of YCs. Detailed finite-element models of YCs are developed and a novel crack propagation simulation scheme is proposed to numerically simulate its ductile fracture initiation, propagation, and associated degradation and regaining of strength due to crack opening and closing. This simulation scheme is validated against 14 small-scale coupon tests and 11 full-scale YC tests. Full-scale test results and the validated model are then used to investigate the influence of in-plane rotation and out-of-plane demands on the overall performance of YC in a nonbuckling concentrically braced frame configuration.