NEESR: Reserve Capacity in New and Existing Low-Ductility Steel Braced Frames

该奖项旨在从基本层面上理解和描述储备能力对低延性钢同心支撑框架抗震性能的影响，直至其倒塌。虽然低延性钢支撑框架具有脆性支撑元件和连接，但如果其重力框架和扣板连接在支撑断裂后起到部分约束作用，则可以实现系统延性。这些部分约束连接形成了一个“备用”弯矩框架系统，即使在主要的抗侧力系统受到严重破坏时，也可以防止侧倒。低震区和中震区钢结构的设计规定隐含地依赖于防止倒塌的储备能力，尽管这种储备能力的性质尚未得到很好的理解，并且可能差异很大。因此，在考虑中等震区的地震设计储备能力时，有必要明确和一致。对储备能力的基本了解将为低、中震区新建筑的设计以及美国所有震区现有建筑的评估建立一个经济可靠的框架，从而为广泛的国家利益提供帮助。这些重要的贡献将通过大规模测试、设计研究、计算模拟和基于可靠性的性能评估的集成来完成。来自伊利诺伊大学厄巴纳-香槟分校和塔夫茨大学的研究小组将使用里海伊大学的小乔治·e·布朗地震工程模拟网络（NEES）设施。与蒙特利尔综合理工学院正在进行的互补研究的合作将提供宝贵的协同机会，并提高研究的影响。该项目的数据将通过NEES项目仓库/数据存储库（http://www.nees.org）.The)存档并向公众开放，该研究开发的系统储备能力的理念和应用将为所有地震区域的结构设计和评估开辟新的可能性，对中等地震区域，高地震区域的改造和特殊结构的设计具有特别重要的意义。工程师将有简单而有效的工具来合理设计和评估低延性结构，利用储备能力来防止地震倒塌。这种储备能力的理念优先考虑降低成本，而不是实现最佳延性水平，这也会对发展中国家的设计产生重大影响，在这些国家，已经成为美国标准的地震细节是负担不起的，也无法用现有技术实现。虽然这项工作的重点是钢结构，但储备能力的范围要广泛得多。一旦在钢铁的背景下被理解，储备能力也可以在美国和国外的其他材料和系统中找到用途。该奖项是国家减少地震灾害计划（NEHRP）的一部分。

This award aims to understand and characterize, at a fundamental level, the influence of reserve capacity on the seismic performance of low-ductility steel concentrically-braced frames up to the point of collapse. Although low-ductility steel braced frames have brittle brace elements and connections, they can achieve system ductility if their gravity framing and gusset plate connections act partially-restrained after braces fracture. These partially-restrained connections form a "reserve" moment frame system that can prevent sidesway collapse even when the primary lateral force resisting system is significantly damaged. Design provisions for steel structures in low and moderate seismic regions implicitly rely on reserve capacity for collapse prevention, even though the nature of this reserve capacity is not well-understood and can vary widely. Thus, there is an essential need for clarity and consistency in considering reserve capacity for seismic design in moderate seismic regions. Foundational understanding of reserve capacity will provide broad national benefit by establishing an economical and reliable framework for design of new buildings in low and moderate seismic regions and for evaluation of existing buildings in all seismic regions of the United States. These significant contributions will be accomplished through integration of large-scale testing, design studies, computational simulations, and reliability-based performance assessments. The research team from the University of Illinois at Urbana-Champaign and Tufts University will use the George E. Brown, Jr. Network for Earthquake Engineering Simulation (NEES) facilities at Lehigh University. Collaboration with complementary research being conducted at Ecole Polytechnique Montreal will provide valuable synergistic opportunities and enhance the research impact. Data from this project will be archived and made available to the public through the NEES Project Warehouse/data repository (http://www.nees.org).The philosophy and application of system reserve capacity developed out of this research will open new possibilities for designing and assessing structures in all seismic regions, with special importance for moderate seismic regions, renovation in high seismic regions, and the design of special structures. Engineers will have simple yet effective tools for rationally designing and assessing low-ductility structures using reserve capacity to prevent seismic collapse. This philosophy of reserve capacity, which prioritizes cost reduction over achieving optimum levels of ductility, can also significantly impact design in developing countries where the seismic details that have become standards in the United States are not affordable or achievable with available technology. While this work focuses on steel structures, the scope of reserve capacity is much broader and more general. Once understood in the context of steel, reserve capacity may also find uses in other materials and systems both in the United States and abroad. This award is part of the National Earthquake Hazards Reduction Program (NEHRP).