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1. Multi-Directional Cyclic Response of Self-Centering Cross-Laminated Timber Shear Walls

   Amer, A. (July 2022, Proceedings of the 12th National Conference on Earthquake Engineering)

   This paper presents an experimental study on the multi-directional cyclic lateral-load response of post-tensioned self-centering (SC) cross-laminated timber (CLT) shear walls. The SC-CLT wall damage states are introduced and qualitatively defined in terms of the level of effort needed to repair the wall to restore its initial functional state. A comparison between SC-CLT wall damage states under unidirectional and multi-directional loading is presented. The experimental test results show that the SC-CLT wall damage state initiation occurs at lower story-drifts under multi-directional loading compared to unidirectional loading. The SC-CLT wall damage states are quantified in terms of the engineering demand parameter (EDP) defined as wall story-drift. Fragility functions that relate the conditional probability of the occurrence of a selected damage state at a wall corner to the EDP are developed. The results reinforce the observations that multi-directional loading on the CLT shear walls causes more damage that unidirectional loading. 

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2. Natural Hazards Research Summit 2022: Establishing Fragility Curves for Seismic Resilience of Mass Timber Buildings with Self-Centering Cross-Laminated Timber Shear Walls

   https://doi.org/10.17603/ds2-7we3-6106  

   Amer, Alia; Ricles, James; Sause, Richard (January 2023, Designsafe-CI)

   Driven by demand for sustainable buildings and a reduction in construction time, mass timber buildings, specifically cross-laminated timber (CLT), is being more widely used in mid-rise buildings in the US. Low damage post-tensioned self-centering (SC) CLT shear walls (SC-CLT walls) provide an opportunity to develop seismically resilient CLT buildings. Previous research focused primarily on the lateral-load response under unidirectional loading of isolated self-centering timber walls, without considering the interaction with the adjacent building structural components, i.e., the floor diaphragms, collector beams, and gravity load system. Buildings response under seismic loading is multidirectional and there are concerns that multidirectional loading may be more damaging to SC-CLT wall panels and the adjacent building structural components than unidirectional loading, which affects the potential seismic resilience of buildings with SC-CLT walls. A series of lateral-load tests of a 0.625-scale timber sub-assembly was conducted at the NHERI Lehigh Large-Scale Multi-Directional Hybrid Simulation Experimental Facility to investigate the the lateral-load response and damage of SC-CLT walls and the capability of the adjacent building structural components i.e., the floor diaphragms, collector beams, and gravity load system to accommodate the building response and the controlled-rocking of the SC-CLT walls under multidirectional lateral loading. 

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3. Multidirectional cyclic testing of self-centering cross-laminated timber shear wall sub-assemblies

   Amer, A. (April 2023, Proceedings of NZSEE 2023 Annual Conference)

   Driven by demand for sustainable buildings and reduction in construction time, mass timber, specifically cross-laminated timber (CLT), is being more widely used in mid-rise buildings in the US. In areas of the US with a significant seismic (i.e. earthquake) hazard, mass timber buildings that are seismically resilient are of significant interest. Low damage post-tensioned self-centering CLT shear walls (SC-CLT walls) provide an opportunity to develop seismically resilient CLT buildings. There is however insufficient knowledge of the lateral-load response and damage states of SC-CLT walls under multidirectional seismic loading conditions, which can have a pronounce effect on the seismic resilience of buildings with SC-CLT walls. In order to fill this knowledge gap, a series of lateral-load tests were performed at the NHERI Lehigh Large-Scale Multi-directional Hybrid Simulation Experimental Facility to investigate the multidirectional cyclic behavior of a low damage, resilient three-dimensional CLT building sub-assembly with SC-CLT coupled shear walls, CLT floor diaphragm, collector beams, and gravity load system. Comparisons are made between the lateral-load experimental response of the SC-CLT walls under unidirectional and multidirectional cyclic loading. 

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4. Experimental Seismic Test of Drywall Partition Walls with Improved Detailing for Damage Reduction

   Ryan, K.; Hasani, H. (July 2020, The 17th World Conference on Earthquake Engineering)

   null (Ed.)

   Drywall partition walls are susceptible to damage at low-level drifts, and hence reducing such damage is key to achieving seismic resiliency in buildings. Prior tests on drywall partition walls have shown that slip track connection detailing leads to better performance than other detailing, such as fully-fixed connections. However, in all prior testing, partition wall performance was evaluated using a unidirectional loading protocol (either in-plane or out-of-plane) or in shake table testing. Moreover, all details are susceptible to considerable damage to wall intersections. Two phases of the test have been performed at the Natural Hazards Engineering Research Infrastructure (NHERI) Lehigh Equipment Facility to develop improved details of drywall partition walls under bidirectional loading. The partition walls were tested alongside a cross-laminated timber (CLT) post-tensioned rocking wall subassembly, wherein the CLT system is under development as a resilient lateral system for tall timber buildings. In the Phase 1, the slip behavior of conventional slip-track detailing was compared to telescoping detailing (track-within-a-track deflection assembly). In the Phase 2, two details for reducing the wall intersection damage were evaluated on traditional slip-track C-shaped walls. First, a corner gap detail was tested. This detail incorporates a gap through the wall intersection to reduce the collision damage at two intersecting walls. Second, a distributed gap detail was tested. In this approach, the aim was to reduce damage by using more frequent control joints through the length of the wall. All walls were tested under a bidirectional loading protocol with three sub-cycles: in-plane, a bi-directional hexagonal load path, and a bi-directional hexagonal load path with an increase in the out-of-plane drift. This loading protocol allows for studying the bidirectional behavior of walls and evaluating the effect of out-of-plane drift on the partition wall resisting force. In the Phase 1, the telescoping detailing performed better than conventional slip track detailing because it eliminated damage to the framing. In Phase 2, the distributed gap detailing delayed damage to about 1% story drift. For the corner gap detailing, the sacrificial corner bead detached at low drifts, but the wall itself was damage-free until 2.5% drift. Bidirectional loading was found to have an insignificant influence on the in-plane resistance of the walls, and the overall resistance of the walls was trivial compared to the CLT rocking. 

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5. Damage assessment of wood frame shear walls subjected to lateral wind load and windborne debris impact

   https://doi.org/10.1016/j.jweia.2020.104091  

   Saini, D.; Shafei, B. (March 2020, Journal of wind engineering and industrial aerodynamics)

   A number of studies have been performed to understand the lateral load carrying capacity of wood frame shear walls. The existing studies, however, have been primarily focused on the intact shear walls, disregarding the possibility of capacity loss due to prior extreme loading events. During windstorms, in particular, windborne debris is the leading cause of damage and destruction. While the impact force induced by windborne debris can directly damage a shear wall, the consequences can become disastrous, as the prior damage adversely affects the in-plane lateral load carrying capacity of the shear wall. This critical aspect motivated the current study to investigate the impact and post-impact performance of wood frame shear walls. For this purpose, a high-fidelity computational framework capable of characterizing both types of damage is developed. Further to providing an in-depth understanding of the process of damage formation and propagation, this study examines how a range of impact scenarios and wall design factors influence the extent of damage that the wood frame shear walls experience in a windstorm. The outcome of this study is then employed to introduce a capacity loss index for the multi-hazard design and assessment of wood frame (and other similar) shear walls in the regions prone to severe windstorms. 

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