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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 

Predetermined Collector Force Histories Tests on AFW were conducted to understand the performance of All Flange Weld (AFW) collector connection under different levels of seismic hazards. A test collector with AFW collector connection, was designed, fabricated, and tested under predetermined seismic collector force and inter-story drift histories, without composite slab and gravity loading. The AFW collector connection demands were obtained from nonlinear time-history analyses of archetype steel buildings. Based on these analyses, representative collector force and story drift demands were selected for the test specimen. Snippets of the loading histories corresponding to different seismic hazard levels were extracted, and each loading history was subdivided as necessary based on force and rotation increments. The selected snippet histories of drift and collector force were applied consecutively. For each loading step, the reaction column was first rotated to the target drift using reaction actuators, followed by application of the corresponding collector force through the loading actuators. This procedure was repeated sequentially until completion of the selected snippet. These tests provide insight into the performance of the AFW collector connection under seismic load demands associated with different earthquake hazard levels. 

Material testing includes concrete compressive strength test and steel tension coupon tests. Concrete cylinder tests were conducted to measure the compressive strength of concrete used for composite slab on MST specimen at different days. Nine 4”x8” concrete cylinders were casted for compressive strength tests. Compressive strength for different days; 14, 21, and 28, were conducted. Compressive strength tests were conducted following ASTM C39. The test were conducted in-house at Lehigh University. Steel tension coupon tests were conducted to measure the material properties of collector specimens and MST shear tab. Plate type 2” gage length tension coupons were used for tensile strength testing. Coupons were extracted from flanges of TFW and AFW specimens, web and shear tab of MST specimen. The tensile strength testings were conducted following ASTM E8. 

Cyclic Collector Force Tests on TFW were conducted to understand the behavior of Top Flange Weld (TFW) collector connection under cyclic collector force (tension and compression) loading. A test collector with top flange weld (TFW) connection, was designed, fabricated, and tested under cyclic collector force without composite slab and gravity loading. The TFW collector connection was subjected to incremental cyclic collector force loading. The loading was performed as a force-controlled loading until the connection yields and switched to deformation-controlled loading after yielding. The cyclic collector force was applied while keeping the reaction column at the fixed position resulting the no rotation on the column. The test provides new knowledge on TFW collector connection properties: strength, stiffness, and deformation capacity. 

Cyclic Collector Force with Rotation Tests on MST were conducted to understand the effect of column rotation on the behavior of Multi-row Bolt Shear Tab (MST) collector connection. A test collector with MST collector connection, was designed, fabricated, and tested under cyclic collector force in presence of forward and backward column rotation with composite slab and in presence of gravity loading. A 2-point gravity loading was applied first to develop the design shear force at the connection. The reaction column was then rotated to prescribed rotation with the help of reaction end actuators while keeping the loading actuators free to move. Then the cyclic collector force loading was applied as force-controlled loading through the loading actuators. The test provides effect of column rotation on MST connection strain demand & evolution, and connection strength. 

Cyclic Collector Force with Rotation Tests on AFW were conducted to understand the effect of column rotation on the behavior of All Flange Weld (AFW) collector connection. A test collector with AFW connection, was designed, fabricated, and tested under cyclic collector force in presence of forward and backward column rotation without composite slab and gravity loading. The reaction column was rotated to prescribed rotation with the help of reaction end actuators while keeping the loading actuators free to move. Then the cyclic collector force loading was applied as force-controlled loading through the loading actuators. The test provides effect of column rotation on AFW connection strain demand & evolution, and connection strength. The connection was subjected to destructive loading after completing all the loading in presence of rotations. 

Cyclic Collector Force with Rotation Tests on TFW were conducted to understand the effect of column rotation on the behavior of Top Flange Weld (TFW) collector connection. A test collector with top flange weld (TFW) connection, was designed, fabricated, and tested under cyclic collector force in presence of forward and backward column rotation without composite slab and gravity loading. The reaction column was rotated to prescribed rotation with the help of reaction end actuators while keeping the loading actuators free to move. Then the cyclic collector force loading was applied as force-controlled loading through the loading actuators. The test provides effect of column rotation on TFW connection strain demand & evolution, and connection strength. The connection was subjected to destructive loading after completing all the loading in presence of rotations.