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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. 

{"Abstract":["To safely survive an earthquake, and thereby protect its occupants, contents, adjacent property, and passersby, a building structure must transfer the large forces that develop during the earthquake from within the building down to the foundation. Earthquake (lateral) forces are generated by the building weight being accelerated horizontally, and thus most earthquake forces originate in the building's heaviest element, i.e., its floors. A key structural element in the force transfer path to the foundation are collectors, which are either special reinforcement in the floor slab or special beams below the slab, that "collect" the forces in the floor, and transfer them to the primary seismic force-resisting vertical elements (frames, braces, or walls). The loss of collectors or collector connections can be catastrophic, as evidenced by the collapse of the CTV building in the 2011 Christchurch, New Zealand earthquake, which killed 115 people, the largest loss of life in this event, and to some extent the collapse of nine parking garages in the 1994 Northridge, California earthquake. Despite the critical nature of seismic collectors, no research effort, including physical testing, has focused specifically on collectors, and knowledge of their seismic performance is lacking. A challenge in understanding the performance of seismic collectors is the complex nature of the floor system itself, a complicated assemblage of many components of different materials (e.g., steel, metal, and concrete) at different elevations, with multiple purposes and uncertain force paths. Past seismic design methodologies for buildings may have significantly underestimated the collector forces. This lack of knowledge impacts not only new construction but also the assessment and retrofit of existing, especially critical care, facilities in high seismic regions. This condition also applies to older non-seismic compliant steel structures nationwide, where inadequate or non-existent seismic collectors are often a major concern. A better understanding of the performance of steel seismic collectors is needed for safe and economical structures, both in the existing building stock and for new construction. Further, the collector's unique role as the critical link between the floor and the vertical elements provides an opportunity for collectors from trying to "out-strength" the earthquake force to instead serve as an innovative force-limiting element that protects the structure from damage. The goals of this research are to: (1) advance knowledge on the seismic performance, analysis, and design of collectors in steel composite floor systems, and (2) develop new knowledge on the reliable seismic performance and potential benefits of innovative collector concepts that can lead to low-damage structural design. This project will support researchers and graduate students from the University of Arizona, University of California, San Diego, and Lehigh University. The project will benefit from working closely with collaborators who are separately supported, i.e., a researcher and a practitioner in New Zealand and an industry panel of seismic design engineers in the United States. An outreach program will be conducted by the University of Arizona with local K-8 schools identified demographically as possessing student bodies of predominately underrepresented groups. The outreach program will target third, fourth, and eighth grade students to include: (1) slides shows and question and answer sessions on earthquake engineering, (2) career mentoring from graduate and undergraduate students, and (3) hands-on science and math activities.\n\nIn this project, an integrated research program will investigate the performance of seismic collectors for steel composite deck structures using the experimental and computational simulation capabilities afforded by the NSF-supported Natural Hazards Engineering Research Infrastructure (NHERI). The research will involve: (1) large-scale testing of collector elements in a steel composite floor system at the NHERI experimental facility at Lehigh University, (2) shake table testing of a 0.4-scale, single-story, steel composite floor system at the NHERI shake table facility at the University of California, San Diego, and (3) nonlinear analysis of steel structure collector elements, details and surrounding regions under seismic effects, and earthquake simulations of steel buildings under strong earthquakes. The planned experiments on steel collectors, with realistic boundary conditions and inertial forces, will be the first of its kind. New data products and calibrated numerical models will be produced from large-scale physical testing. Analytical models will be developed for the collectors and the collector inertial force paths. Transfer of research results into practice will include: (1) new concepts for low-damage structural design, (2) research-based design recommendations, and (3) assessment and retrofit guidelines."]} 

This paper presents an experimental study on the multidirectional cyclic lateral-load response of repaired post-tensioned self-centering (SC) controlled-rocking cross-laminated timber (CLT) shear walls (SC-CLT walls). Three SC-CLT wall specimens were investigated: an initially undamaged SC-CLT wall with unreinforced wall panels, a repaired SC-CLT wall with steel-plate reinforcement, and a repaired SC-CLT wall with steel-plate reinforcement and steel bearing plates on the foundation. An evaluation of the experimental response of SC-CLT walls (with and without steel-plate reinforcement) under multidirectional cyclic lateral loading is presented, with emphasis on changes in lateral stiffness and strength caused by damage. Steel-plate wall panel reinforcement is investigated as a repair approach to restore the lateral stiffness and strength of damaged SC-CLT walls. Steel bearing plates are used to repair (or avoid) localized damage to a concrete foundation when a steel plate–reinforced SC-CLT wall rocks on the foundation. The damage mechanisms affecting the changes in lateral stiffness and strength of each SC-CLT wall specimen are discussed. Assessment of the experimental results demonstrate that these repair methods are effective in restoring the lateral stiffness and strength of a damaged SC-CLT wall 

Real-time Hybrid Simulation (RTHS) is a technique wherein a structural system is divided into an analytical and an experimental substructure. The former is modeled numerically while the latter is physically present in the laboratory. The two substructures are kinematically linked together at their interface degrees of freedom (DOFs) and the equations of motion are solved in real-time to determine the structure’s response. One of the main challenges of RTHS is to include the effects of soil–foundation–structure interaction (SFSI), which can have a substantial effect on the overall response. The soil domain cannot be modeled experimentally due to the large payload size. On the other hand, modeling the soil domain numerically, using a continuum-based approach, in real-time is challenging due to the associated computational cost. To address these issues, this paper presents a framework for seismic RTHS of SFSI systems using a Neural Network (NN)-based macroelement model of the soil–foundation system. A coupled SFSI model is used to train the NN model and the loss function is based on dynamic equilibrium at the interface between the foundation and the structure. The framework is demonstrated using a three-story building with the lateral load resisting system comprised of moment resisting and damped brace frames. The proposed framework ensures a stable and accurate RTHS, accounting for SFSI by incorporating: (a) spring elements at the output DOFs of the NN model to remove rigid body modes; (b) dashpot elements at the output DOFs of the NN model to mitigate spurious higher frequencies of vibration; and (c) regularization in the NN model’s architecture with data augmentation to reduce overfitting. 

Abstract This study investigates the experimental response of a hybrid shape memory alloy (SMA) cable-friction damping device with a specific focus on the failure behavior and reparability of the damper when tested at extreme deformations. The superelastic friction damper (SFD) is a hybrid seismic protection device that combines the high tensile strength and re-centering capability of superelastic SMA cables with stable, repeatable energy dissipation of a friction-based damping system. In this paper, the fabrication of a prototype damper and its experimental testing are discussed. The response of the SFD’s friction and self-centering mechanisms were separately evaluated considering design level deformations, cyclic loading, and large deformations up to failure. The performance of the device after the repair of failed components was also investigated. Findings from the study show that the SFD reached failure at a deformation level that exceeded the design displacement by a factor of 2.2. The force capacity of the SFD at the failure stage was 46% higher than the maximum force at the design deformations. After replacing the failed SMA cables, the damper’s mechanical response was identical to the pre-failure response, illustrating the device’s ability to be restored without hindering performance.