Shake Table Testing of a Steel Building with Seismic Collectors: Global Responses and Observed Damage

Seismic collectors are critical structural elements that transfer inertial forces from floor and roof diaphragms to the vertical-plane seismic force-resisting system (SFRS) during an earthquake. In steel buildings, collectors are typically provided by special reinforcement in the floor slab or by steel beams in the floor or roof level. Despite its critical role in the seismic load path, research on collectors is limited. A two-phase test program was conducted on a half-scale, two-story steel building with seismic collectors in a composite floor slab and a bare steel roof deck, using the NHERI@UCSD large high-performance outdoor shake table. The aim was to investigate the force path and seismic response of steel collectors and various collector-to-column connections under realistic conditions. Phase 1 involved testing a single-story phase with only the first story and a composite slab. Simulated input motions were used to reproduce target floor absolute acceleration time histories from a multistory prototype building model. Phase 2 tests were performed conventionally after adding a second story with a bare steel roof deck, using historical ground motions for the input. This paper describes the test program and global responses of the test building. The observed damage offers design recommendations for a type of collector-to-column connection using complete joint penetration (CJP) groove welds in both flanges of the collectors.