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Phase 3 incorporated Buckling-Restrained Braced Frames (BRBFs) into the two-story test building to evaluate collector behavior in the presence of a yielding seismic-force-resisting system. Conventional earthquake simulation was used with scaled ground motions from the 1994 Northridge Earthquake (Beverly Hills-14145 Mulhol.) at 50%, 100%, 150%, and 200% Design Earthquake (DE) levels, including sign-reversed motions. White-noise and impulse tests were used to identify and track dynamic properties. This phase enabled assessment of collector axial force, slab participation, and connection rotation under system-level interaction with brace yielding and load redistribution. For Phase 3, Buckling-Restrained Braced Frames (BRBFs) were added to the same two-story building used in Phases 2. The diaphragm, collector, and connection details remained the same. This specimen was used to evaluate collector behavior in a yielding structural system, including the interaction between diaphragm inertial forces, brace yielding, and load redistribution. Earthquake events consisted of acceleration time histories based on the 1994 Northridge Earthquake record (Beverly Hills-14145 Mulhol.), scaled to different Design Earthquake (DE) intensity levels. Motions were applied in both direct and sign-reversed directions. These events were used to evaluate collector forces, slab participation, inter-story drift, and connection behavior under increasing levels of seismic demand. 

Phase 2A used a two-story steel test building with a composite-slab second floor and a bare-steel roof deck. Added weight was applied only at the second floor. Conventional earthquake simulation was used with scaled ground motions from the 1994 Northridge Earthquake (Beverly Hills-14145 Mulhol.) at 50%, 100%, and 200% Design Earthquake (DE) levels, including sign-reversed motions. White-noise and impulse tests were used to identify dynamic properties. In this phase, the second-floor collectors experienced significant axial forces from diaphragm inertial loading, while the roof collectors were mainly subjected to flexural demands due to negligible roof mass. The Phase 2A specimen was a two-story steel building constructed by adding a second story onto the existing Phase 1 test building. It had a composite-slab second floor, a bare-steel roof deck, and perimeter collectors at both levels. Added mass was installed only at the second floor to generate diaphragm inertial forces during the earthquake-simulation tests. This configuration allowed evaluation of collector behavior when significant axial force developed primarily in the second-floor collectors, while the roof collectors experienced mainly flexural demand associated with story drift. 

Phase 2B used the same two-story configuration as 2A, but added weight at both the second floor and roof to increase diaphragm inertial forces. Testing again used scaled Northridge motions (Beverly Hills-14145 Mulhol.) at 50%, 100%, and 125% DE levels, including sign-reversed and repeat motions, with white-noise and impulse tests used to track system properties. In this phase, both the roof and second-floor collectors developed substantial axial forces in addition to flexural demands from story drift, allowing evaluation of collector-to-column connections under combined axial–flexural loading The Phase 2B specimen had the same structural configuration and collector detailing as Phase 2A, but added mass was installed at both the second floor and roof. This produced diaphragm inertial loading at both levels, leading to combined axial and flexural demands in the collectors and their connections. The Phase 2B specimen allowed direct comparison with Phase 2A to study the influence of mass distribution on collector forces. 

Phase 1 used a single-story steel test building with a composite slab and perimeter collectors to develop and validate a Floor Acceleration Simulation Testing (FAST) methodology intended to reproduce multistory floor accelerations in a single-story test frame. White-noise and impulse tests were used to identify dynamic properties, followed by earthquake simulation tests at 20%, 50%, and 100% Design Earthquake (DE) levels to observe collector axial force, slab participation, and connection rotation. White-noise tests: White-noise excitation was applied at low amplitude to identify the natural frequencies, damping ratios, and stiffness characteristics of the structure. These tests were typically conducted before and after earthquake events to track changes in dynamic properties as damage accumulated. Impulse tests: Single-pulse excitation was applied through the shake table to evaluate the transient dynamic characteristics of the structure and to supplement the system-identification testing performed using white-noise input. Floor Acceleration Simulation Testing (FAST): In FAST, the objective was to reproduce realistic multistory floor acceleration demands in a single-story test building. Target floor-acceleration histories were obtained from nonlinear response-history analyses of a 12-story BRBF prototype building (SDII). A transfer-function approach in the frequency domain was then used to compute the shake-table input motion required for the single-story specimen to generate these target accelerations. This approach allowed the specimen to respond essentially elastically while reproducing the amplitude and frequency content of multistory floor accelerations. Earthquake simulation tests: Earthquake events consisted of acceleration time histories based on the 1994 Northridge Earthquake record (Beverly Hills-14145 Mulhol.), scaled to different Design Earthquake (DE) intensity levels. Motions were applied in both direct and sign-reversed directions. These events were used to evaluate collector forces, slab parti 

ABSTRACT This study integrates analytical and experimental research to develop an innovative shake table testing method called Floor Acceleration Simulation Test (FAST). The primary objective of FAST is to produce an essentially elastic response of a single‐story test specimen to replicate the floor acceleration time history including higher‐mode effects of a target floor in a multistory building experiencing inelastic behavior during an earthquake. The FAST method is well suited for experimental research where the absolute accelerations and the associated inertial forces of the floor diaphragms cannot be simulated by the majority of the conventional test methods. The proposed methodology is based on a transfer function in the frequency domain to compute the required input motion for testing. Considering the physical constraints of a given shake table test facility, guidelines with two response spectra to bracket the natural frequency of the test building are also presented for practical implementation. Experimental validation was carried out on a half‐scale, single‐story steel building featuring a composite floor slab, utilizing the NHERI@UCSD Large High‐Performance Outdoor Shake Table (LHPOST) facility. The results demonstrate the effectiveness of FAST, as both analytical predictions and experimental outcomes confirm its validity. Despite instances of measured floor acceleration amplitude exceeding the target response due to table input motion overshooting in this test program, test results confirmed that the FAST accurately reproduced the intended frequency content, indicative of higher mode effects in the multistory prototype building, in the single‐story test building.