Full-Scale Tests of Gapped-Inclined Bracing System: Seismic Retrofit for Soft-Story Buildings

Abstract

This paper presents the results of full-scale experimental validations of the gapped-inclined bracing (GIB) system, a novel structural device for the seismic retrofit of soft-story buildings. The experiment consisted of three phases. Phase I tested a single brace to investigate its constructability and characterize its component-level performance. The second and third phases compared the reversed-cyclic response of two full-scale RC single-bay, single-story frames representing the soft story of a six-story RC frame: a conventional frame and the same frame retrofitted with GIBs. With the results observed from Phase I, the design considerations and constructability of the GIB system were improved for Phase III. The results of Phases II and III demonstrate that the GIB system significantly increases the lateral drift capacity of the RC frame, shifting strength degradation from ±1.5% for the original frame to more than ±4.0% drift for the retrofitted frame. In addition, even after considerable damage to the columns, the retrofitted frame was able to undergo repeated cycles of up to 7.0% drift without compromising its gravity load-bearing capacity, revealing that the damaged frame develops a stable GIB-only rocking response for large drifts.