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1. Design, Fabrication, and Assembly of a Tessellated Precast Concrete Shear Wall

   Fulmer, Grace; Ross, Brandon E.; Kleiss, Michael; Okumus, Pinar; Elhami, Negar; Romero, John Michael (May 2021, Precast/Prestressed Concrete Institute National Convention)

   This paper describes the fabrication and assembly of tessellated precast reinforced concrete shear walls. These walls are being constructed and tested as part of an NSF-funded research project designed to demonstrate the concept of Tessellated Structural-Architectural (TeSA) systems. The over-arching goal of this research is to explore tessellation patterns that can be implemented on a large scale, are architecturally appealing, and provide structural function. TeSA systems are comprised of individual tiles arranged in tessellations, or repeating geometric patterns. Tiles are topologically interlocking, which means that they transfer forces due to their interlocking geometry rather than through a bonding adhesive. The benefit of such a system is the ability to localize failure and rapidly repair the individual damaged tiles, rather than the entire system. The specimen discussed in this paper is a precast concrete shear wall constructed from individually cast I-shaped tiles. Shear wall tests are forthcoming; this paper focuses instead on documenting technical solutions to difficulties faced during design, fabrication, and assembly of the test specimen. This paper is intended to provide lessons learned to others who are designing and building TeSA walls and thereby facilitate the benefits of these novel systems. 

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2. Undergraduate Student Experience in a Multidisciplinary Architecture-Civil Engineering Research Project

   Crocker, G; Bender, K; Blasiak, R; Lang, J; Moore, S; Wright, O; Dai, S; Syed, M; Elhami-Khorasani, N; Kleiss, M; et al (April 2022, 2022 American Society for Engineering Education (ASEE) Southeastern Section Conference)

   This paper examines the learning experiences of undergraduate students who conducted research as part of a multidisciplinary team. The research project involved five undergraduate students with different backgrounds in engineering as well as in arts and sciences, supervised by four architecture and civil engineering faculty and their three PhD students. The research investigates the behavior of new Tessellated Structural-Architectural (TeSA) systems made of repetitive patterns of tiles (tessellations) that are both aesthetically appealing and load bearing. The undergraduate students worked on three tasks: (1) studying the behavior of TeSA shear walls using small scale earthquake simulator tests, (2) studying the shear capacity of reinforced concrete TeSA tiles, and (3) studying the effect of different shapes and interlocking patterns on the performance of small scale TeSA beams. The undergraduate students used hands-on experiments and laboratory testing to study the performance of 3D printed or prefabricated interlocking tessellations. This paper discusses the technical skills, fundamental concepts, and power skills (communicating, writing, presenting, etc.) that the students obtained, as well as the challenges that they encountered. The students found the process of developing and executing hands-on experiments and analyzing experimental results effective for learning new technologies and fundamental concepts. These concepts included 3D printing methods, natural frequency of a structure, and structural response subjected to a shear force. Peer learning, collaboration between students with different backgrounds, and group discussions with all the team members facilitated a deeper understanding and broader perspective on design, performance, and construction of TeSA systems. The project took place during the COVID-19 pandemic, and the students found working and meeting remotely challenging at times. Proper guidance and timely feedback by the project investigators and their PhD students helped with resolving the challenges. 

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3. Lateral response of post-tensioned pendulum shear walls

   https://doi.org/10.1016/j.istruc.2024.106987  

   Silva, PF; Lagler, C; Burgueño, R (July 2024, Structures)

   This paper presents an experimental evaluation of a new interface configuration for unbonded post-tensioned shear (UPTS) walls. In the proposed configuration, the wall-base interface is shaped in a circular profile. This circular profile presents a major difference from the currently used flat profile at the wall-base interface of rocking UPTS walls. During lateral response, this circular profile induces the wall to predominantly rotate as a rigid body about a fixed point without uplift, and the system dissipates energy through the contact friction that develops at the wall-base interface. This rigid body motion resembles that of a pendulum, thereby designating this system as a pendulum UPTS wall. At this stage, research has demonstrated the many advantages of this system by proof-of-concept testing of a pendulum light-frame wood (LiF) UPTS wall specimen under increasing levels of post-tensioning force. Compared with rocking UPTS walls, experimental results demonstrate that besides performing damage-free when subjected to high drift levels, the proof-of-concept pendulum LiF-UPTS wall offers the following promising outcomes: (1) insignificant to no wall uplift, (2) insignificant to no wall base shear sliding, (3) reduced stress concentrations at the wall toes because contact stresses are distributed along the wall-base interface over a larger region, (4) nearly constant post-tensioning forces under high drift levels, which limits post-tensioning losses due to yielding of prestressing bars or tendons, (5) increase in energy dissipation capacity of the system through friction, and (6) decrease in the damping reduction factor and thus, reduction in the lateral displacement and force demands in pendulum LiF-UPTS walls. These research outcomes are likely to translate positively to other shear wall types, namely reinforced concrete (RC) precast pendulum UPTS walls. 

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4. Lateral response of post-tensioned pendulum shear walls

   Silva, Pedro; Lagler, Carmen; Burgueño, Rigoberto (September 2024, Structures)

   Leroy, Gardner (Ed.)

   This paper presents an experimental evaluation of a new interface configuration for unbonded post-tensioned shear (UPTS) walls. In the proposed configuration, the wall-base interface is shaped in a circular profile. This circular profile presents a major difference from the currently used flat profile at the wall-base interface of rocking UPTS walls. During lateral response, this circular profile induces the wall to predominantly rotate as a rigid body about a fixed point without uplift, and the system dissipates energy through the contact friction that develops at the wall-base interface. This rigid body motion resembles that of a pendulum, thereby designating this system as a pendulum UPTS wall. At this stage, research has demonstrated the many advantages of this system by proof-of-concept testing of a pendulum light-frame wood (LiF) UPTS wall specimen under increasing levels of post-tensioning force. Compared with rocking UPTS walls, experimental results demonstrate that besides performing dam-age-free when subjected to high drift levels, the proof-of-concept pendulum LiF-UPTS wall offers the following promising outcomes: (1) insignificant to no wall uplift, (2) insignificant to no wall base shear sliding, (3) reduced stress concentrations at the wall toes because contact stresses are distributed along the wall-base interface over a larger region, (4) nearly constant post-tensioning forces under high drift levels, which limits post-tensioning losses due to yielding of prestressing bars or tendons, (5) increase in energy dissipation capacity of the system through friction, and (6) decrease in the damping reduction factor and thus, reduction in the lateral displacement and force demands in pendulum LiF-UPTS walls. These research outcomes are likely to translate positively to other shear wall types, namely reinforced concrete (RC) precast pendulum UPTS walls. 

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5. A study on Residual Drift and Concrete Strains in Unbonded Post-Tensioned Precast Rocking Walls

   Sharma, Sumedh; Aaleti, Sriram (June 2019, Proceedings of the ... Canadian Conference on Earthquake Engineering)

   Modern seismic resistant design has been focusing on development of cost effective structural systems which experience minimal damage during an earthquake. Unbonded post-tensioned precast concrete walls provide a suitable solution due to their self-centering behavior and their ability to undergo large nonlinear deformation with minimal damage. Several experimental and analytical investigation focusing on lateral load resisting behavior of unbonded post-tensioned precast walls has been carried out in the past two decades. These investigations have primarily focused on lateral load resistance, self-centering capacity, energy dissipation and extent of damage in confined concrete region of the wall system. Past experimental results have shown that self-centering capacity of the wall system decreases at higher lateral drifts. Particularly, rocking walls with higher energy dissipation capacity, sustain considerable residual displacement. This residual displacement in the wall system may affect the ability of the entire structure to re-center. Though increasing initial prestressing force helps in reducing residual drift, it also subjects concrete to increased axial compressive stress which may lead to premature strength degradation of confined concrete in rocking corners. Accurate prediction of expected concrete strains in confined regions during increasing drift cycle is critical in design of such wall systems. Simplified design procedures available in literature assume different values for plastic hinge length to estimate critical concrete strain values. The results from the experimental tests available in literature were analyzed, to understand the effects of energy dissipating elements on residual drift and to examine the accuracy of simplified design procedures in predicting critical concrete strain. Based on the findings, recommendations are made on design of energy dissipating elements and plastic hinge length for unbonded post-tensioned precast rocking walls. 

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