Collaborative Research: Self-Centering Pendulum Shear Walls in Buildings via Nonlinear Elastic Kinematics

结构工程中的一个重大挑战是开发能够抵抗极端自然灾害(如飓风或地震)的荷载的建筑系统，而损害最小或没有损害。这样的建筑系统可以在极端事件发生后立即入住率和最大限度地减少经济损失，为国家的持续繁荣和福祉做出贡献。随着建筑中无粘结、后张拉剪力墙(UPSWs)的发展，在解决这一挑战方面取得了进展；但设计此类剪力墙的局限性问题仍然存在。这项研究将探索结构剪力墙的创新概念，以抵抗建筑物的横向荷载，并在极端事件中实现无破坏。该概念由连体、无粘结、后张法、钢筋混凝土墙组成，通过曲面与基础相互作用。当墙沿底部曲面滑动时，将通过摆式运动来适应横向变形。横向阻力将通过沿曲面和垂直无粘结后张拉索的摩擦来提供。后张拉索还将有助于将墙恢复到其初始配置。这些双摆墙的能量耗散将通过加入连接装置来提供，这些连接装置使用弹性屈曲并在墙的变形过程中释放累积的弹性能量。因此，系统响应将利用由此产生的变形，而不是像传统系统那样试图限制它们。其结果将是与无损结构建筑系统设计相关的新技术，以及利用系统几何和变形来增强弹性和可持续建筑的新思维方式。与研究工作并行的还有互补的教育和宣传部分，包括培训两名博士生，为本科生提供研究经验，为本科生和研究生和实践者建立一个项目网站，提供教程和研究成果，以及为初中生和高中生开展外联活动。这些教程以及该项目的数据也将在美国国家科学基金会支持的自然灾害工程研究基础设施数据库(https://www.designsafe-ci.org).)中公开提供这项研究的核心思想是一种新的设计理念，设想不受传统材料失效极限状态的限制。这一理念将通过对偶联的万国邮政开关的新概念加以验证。通过利用耦合系统变形引起的非线性运动学行为，将解决摇摆UPSWs的材料响应限制问题。因此，该项目的目标是开发一种新的概念UPSWs的使能理论和技术，该概念可以执行无损伤和不受材料失效极限状态限制的UPSWs。这一目标将通过两个独特和互补的特征来实现：(1)单个墙体沿着圆形路径滑动，在基础界面没有分离，(2)通过沿垂直墙体接缝具有可控弹性不稳定性的装置连续消能。这一概念将被指定为钟摆UPSW系统，因为它绕着墙上的一个固定点旋转。下一步的工作将是将单摆超静定结构的面内响应描述为可行的抗侧向载荷单元，发展和描述利用弹性超材料和超结构通过弹性不稳定来耗散能量，以及描述以弹性多稳态结构为连接件的单摆超静定结构的响应。将使用分析、数值(有限元)和实验相结合的方法。这项研究将导致系统几何和变形的基本结合，以设计具有弹性和可持续性的抗侧向载荷结构。这项研究将促进新的设计理念，利用变形来实现最佳性能，而不是以材料极限状态为目标的性能目标。该研究还将有助于非线性弹性不稳定性在大型结构系统中的应用。与无损结构系统、摩擦模型和弹性能量耗散装置相关的理论和方法也将得到改进。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

A grand challenge in structural engineering is to develop building systems that can resist loads from extreme natural hazards, such as hurricanes or earthquakes, with minimum or no damage. Such building systems could enable immediate occupancy and minimum economic losses after an extreme event, contributing to continued national prosperity and welfare. Progress has been made towards addressing this challenge with the development of unbonded, post-tensioned, shear walls (UPSWs) in buildings; yet limiting issues for designing such shear walls remain. This research will explore an innovative concept for structural shear walls to resist lateral loads in buildings and perform damage free during an extreme event. The concept consists of coupled, unbonded, post-tensioned, reinforced concrete walls that interact with the foundation via a curved surface. Lateral deformations will be accommodated through a pendulum-type motion as the wall slides along the bottom curved surface. Lateral resistance will be provided by friction along the curved surface and the vertical unbonded post-tensioned cables. The post-tensioned cables also will help restore the wall to its initial configuration. Energy dissipation of these coupled pendulum walls will be provided by incorporating connecting devices that use elastic buckling and release accumulated elastic energy during the walls' deformations. The system response thus will leverage the resulting deformations rather than trying to constrain them, as in traditional systems. The result will be new technology related to the design of damage-free structural building systems, and a new way of thinking about leveraging system geometry and deformations for enhanced resilient and sustainable buildings. Parallel to the research effort will be complementary educational and outreach components, including the training of two Ph.D. students, research experiences for undergraduate students, a project website with tutorials and research findings for undergraduate and graduate students and practitioners, and outreach activities for middle and high school students. The tutorials, as well as data from this project, also will be made publicly available in the NSF-supported Natural Hazards Engineering Research Infrastructure Data Depot (https://www.designsafe-ci.org). The core idea of this research is that of a new design philosophy envisioned to be unrestricted by traditional material failure limit states. This philosophy will be verified through a new concept for coupled UPSWs. The material response limitations of rocking UPSWs will be addressed by harnessing the nonlinear kinematic behavior resulting from coupled system deformations. Thus, the project objective is to develop the enabling theory and technology for a new concept of UPSWs that can perform damage free and unrestricted by material failure limit states. This objective will be achieved through two unique and complementary features: (1) individual walls gliding along a circular path with no separation at the footing interface, and (2) continuous energy dissipation via devices with controllable elastic instabilities along vertical wall joints. This concept will be designated as a pendulum UPSW system, as it rotates about a fixed point on the wall. The approach to be followed will be to characterize the in-plane response of pendulum UPSWs as viable lateral load resisting elements, develop and characterize the use of elastic meta-materials and meta-structures for dissipating energy via elastic instabilities, and characterize the response of pendulum UPSWs coupled with elastic multi-stable structures as connectors. A combination of analytical, numerical (finite element), and experimental methods will be used. This research will lead to the fundamental integration of system geometry and deformations for the design of lateral load resisting structures that are resilient and sustainable. The study will promote new design concepts that harness deformations for optimal performance rather than performance objectives set to target material limit states. The research also will contribute to the use of nonlinear elastic instabilities in large-scale structural systems. Theory and methods related to damage-free structural systems, friction models, and elastic energy dissipation devices will also be advanced.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.