NEESR-CR: Unbonded Post-Tensioned Rocking Walls for Seismic Resilient Structures

该奖项是NSF 09-524项目征集“小乔治·E·布朗地震工程模拟(NEES)研究网络(NEESR)”竞赛的结果，包括爱荷华州立大学(ISU)以及明尼苏达大学的两个校区：双子城(UMN)和德卢斯(UMD)。该项目将利用位于曼彻斯特大学和内华达大学里诺分校的NEES设施。这项研究的动机是地震造成的破坏和随后的经济损失，突出了重点发展抗震建筑的必要性。实现弹性建筑的一种方法是用自中心结构体系来设计它们，以抵御地震横向荷载。使用无粘结后张拉筋，ISU开发了一种名为PreWEC的具有成本效益的自定心墙体系(即带有两个端柱的预制墙)，该体系已被分析和试验证明具有良好的抗震性能，结构破坏最小。在该体系中，以及采用无粘结后张法设计的单层摇摆墙(SRW)中，响应以摇摆模式为主。然而，由于对这方面的认识不足，在设计中还没有考虑到墙体在摇摆过程中撞击地基所造成的能量损失。有重要证据表明，仅这一机制可能就足以消散地震能量。此外，包含摇摆墙的建筑的弹性还取决于周围结构组件的行为，特别是楼板和重力柱，以及它们与抗震系统的相互作用。为了确保结构的完全弹性，这些相互作用应该通过了解墙-地板连接反应来解决。智力优势：与日本E-Defense和新西兰奥克兰大学的研究人员合作，该项目的智力优势是利用SRW和PreWEC的地震摇动基本特征开发出具有地震弹性的建筑解决方案。通过一个国际、跨学科的专家团队和两个NEES设施，该项目将通过完成以下目标来实现这一目标：1)通过NEES/国际试验了解自定心墙地震摇摆的基本特征，从而识别不同的能量耗散源(即冲击能量损失、粘性阻尼和滞回阻尼)；2)在摇动墙和楼板之间建立适当的连接，并通过大规模试验量化墙-地坪-柱的相互作用；3)通过对无粘结筋的足够锚固来确保摇摆系统的安全；4)设计具有地震弹性的结构；5)改进用摇摆墙和不同地板系统设计的建筑的数值模拟；6)制定设计指南；以及7)教育学生、从业者和其他人(如政策制定者)关于拟议研究的意义。更广泛的影响：该奖项还具有几个更广泛的影响。首先，它为来自不同人群的研究生和本科生提供了几个独特的机会，让他们在分布式的NEES环境中参与国际研究团队并与其合作。其次，它促进了未被充分代表的学生参与土木工程，并向K-12学生介绍了新的NEES协作模式和摇摆墙在抗震设计中的好处。研究团队将为项目领先(PLTW)做出贡献，该项目旨在通过让初中生接触工程课程来为大学水平的工程教育做好准备。UMD将在明尼苏达州北部的学校，包括部落学校，试行拟议的PLTW计划。下一步，将通过整合研究成果来开发一个独特的、面向团队的课程模块，以便它可以用于研究生和本科生的教学。该单元将通过NEEShub向地震工程界提供。利用项目内计划的NEES协作，项目组还将为推进NEES远程呈现技术做出贡献。最后，拟议的项目将加强三个参与机构的研究和教育，其中包括一所以本科生为主的大学。所有预期的项目成果最终将产生在地震区设计更安全、更具弹性的建筑所需的新的基本知识，从而为美国和世界各地的地震灾害缓解做出贡献。该项目的数据将被存档，并通过NEES数据库向公众提供。该奖项是国家减少地震灾害计划(NEHRP)的一部分。

This award is an outcome of the NSF 09-524 program solicitation "George E. Brown, Jr. Network for Earthquake Engineering Simulation (NEES) Research (NEESR)" competition and includes Iowa State University (ISU) as well as two University of Minnesota campuses: Twin Cities (UMN) and Duluth (UMD). This project will utilize the NEES facilities located at UMN and the University of Nevada at Reno.The motivation for this research is that damage caused by earthquakes, and the subsequent economic losses, underscore the need to focus on developing earthquake resilient buildings. One method of achieving resilient buildings is to design them with self-centering structural systems to resist earthquake lateral loads. Using unbonded post-tensioning tendons, a cost-effective, self-centering wall system known as PreWEC (i.e., Precast Wall with two End Columns) was developed at ISU, which has been proven analytically and experimentally to have excellent seismic performance with minimal structural damage. In this system, as well as in single rocking walls (SRWs) designed with unbonded post-tensioning, the response is dominated by a rocking mode. However, the energy loss caused by the wall impacting the foundation during rocking has not been given consideration in design due to lack of knowledge on this subject. Significant evidence suggests that this mechanism alone may be sufficient to dissipate the seismic energy. Furthermore, the resilience of a building containing rocking walls is also dependent on the behavior of surrounding structural components, especially floors and gravity columns, and their interactions with the seismic resistant systems. To ensure a fully resilient structure, these interactions should be addressed by understanding the wall-floor connection responses. Intellectual Merit: In collaboration with E-Defense in Japan and researchers at the University of Auckland in New Zealand, the intellectual merit of this project is the development of seismic resilient building solutions utilizing the fundamental characteristics of seismic rocking of both SRWs and PreWECs. By involving an international, cross-disciplinary team of experts and two NEES facilities, the project will accomplish this goal by completing the following objectives: 1) understand the fundamental characteristics of seismic rocking of self-centering walls through NEES/international tests, thereby identifying different energy dissipation sources (i.e., energy loss due to impact, viscous damping and hysteretic damping); 2) develop suitable connections between rocking walls and floors, and quantify the wall-floor-column interactions using large-scale tests; 3) ensure safety of the rocking systems through sufficient anchorage of the unbonded tendons; 4) design seismic resilient structures; 5) improve numerical simulation of buildings designed with rocking walls and different floor systems; 6) formulate design guidelines; and 7) educate students, practitioners, and others (e.g., policymakers) on the significance of the proposed study.Broader Impacts: This award also has several broader impacts. First, it offers several unique opportunities for graduate and undergraduate students from diverse populations to participate and collaborate with an international team of researchers in a distributed NEES environment. Second, it promotes the participation of underrepresented students in civil engineering and introduces K-12 students to the new NEES collaboration model and benefits of rocking walls in seismic resistant design. The research team will contribute to Project Lead the Way (PLTW), a program designed to prepare middle and high school students for college-level engineering education by exposing them to engineering courses. UMD will pilot the proposed PLTW program at schools in northern Minnesota, including tribal schools. Next, a unique, team-oriented course module will be developed by integrating the research outcomes so that it can be used for instruction at the graduate and undergraduate levels. This module will be made available to the earthquake engineering community through NEEShub. Using the planned NEES collaboration within the project, the project team will also contribute to advancing NEES telepresence technologies. Finally, the proposed project will enhance research and education at the three participating institutions, which includes a predominantly undergraduate university. All anticipated project outcomes will ultimately produce new basic knowledge needed to design safer, more resilient buildings in seismic regions and thus contribute to seismic hazard mitigation in the United States and around the world. Data from this project will be archived and made available to the public through the NEES data repository. This award is part of the National Earthquake Hazards Reduction Program (NEHRP).