Restoring force model of end-plate bolted shear links in eccentrically braced frames

Abstract

The eccentrically braced frame with end-plate bolted shear links provides both the necessary seismic performance and a cost-effective post-earthquake repair system. In this paper a more accurate and sophisticated restoring force model was developed to describe the mechanical properties and hysteresis behavior of widely stiffened I-shape shear links with bolted end-plate connections. Cyclic loading tests were performed on 18 link specimens to investigate the post-buckling behavior and ultimate capacity of this type of members. The key observations concerning the characteristic diagonal shear buckling of the web and the development of plastic hinges in the flanges exhibited by the web panel at failure were discussed, and the key factors affecting the mechanical properties of shear links were also investigated. Further, the forms of tension field distribution and failure modes for framing web panels of the specimens with different stiffener layouts were determined. The Cardiff's tension field method was employed to predict the post-buckling strength and collapse loads of link models, and the regression analysis integrating link major configurations was used to give the stiffness expressions of multi-linear model. The hysteresis curve parameters were calibrated based on the experimental results and given by simple expressions. The comparison between numerical and laboratory results shows an accurate evaluation of the response of the widely stiffened I-shape shear links. Finally, the applicability of the proposed model is shown by means of comparing with other link models often used in eccentrically braced frames.