Experimental study of improved seismic behaviour of eccentrically braced frames by zipper elements

The performance and behaviour of a novel seismic-resistant system known as the zipper eccentrically braced frame (ZEBF) was investigated. The ZEBF merges the advantages of eccentrically braced steel frames with zipper elements to enhance the strength, stiffness, ductility and energy dissipation of structures under earthquake loading. The system consists of four main components - the zipper element, a diagonal brace element, a link element and column elements. The zipper and link elements act as fuses, forming plastic hinges under moderate and severe lateral loads, and can be replaced after a major earthquake. The experimental evaluation involved three half-scale specimens subjected to the ATC-24 protocol. The results demonstrated that, compared with conventional systems, the ZEBF significantly increased both shear strength and cumulative energy dissipation. The seismic performance of the ZEBF was further assessed numerically using OpenSees software and incremental dynamic analysis, evaluating the probabilistic seismic performance of 4-, 8- and 12-storey residential buildings with different lateral systems (concentrically braced frames, eccentrically braced frames and ZEBFs) based on performance-based earthquake engineering.