ERI: Segmented Braces for Improved Seismic Performance and Repairability of Concentrically Braced Frames

该工程研究启动奖(ERI)将为钢支撑框架开发一种新的抗震设计方法，该方法使用分段支撑配置用于地震后的快速修复。在美国，在易受地震危害的地区建造的建筑物被设计为在大地震期间保持安全，但结构部件，如对角撑，设计为在耗散地震能量的同时承受破坏。在受地震影响的社区，这种建筑破坏可能是严重的和广泛的，抑制了地震后入住率、功能和修复的速度或可能性。钢支撑框架在现有建筑基础设施中非常普遍，用途广泛，包括医院、学校、办公室和工业设施，这些设施对于震后避难所和人们的护理、货物分配和经济生产力至关重要。分段支撑方案将减轻这些常见系统中地震破坏的影响，并通过实现相对快速、低成本的跨中支撑更换来增强地震弹性，从而使大多数其他系统组件能够安全保留。试验测试将调查应用于新的建筑和维修方案的分段支撑的抗震性能。随之而来的一项计算研究将扩展这些发现，以评估其他设计参数，以制定适用于工程实践的设计程序和建模建议。研究活动将被纳入结构钢设计实验室体验课程模块，并通过本科生研究机会和推广计划吸引未被充分代表的群体参与工程。该奖项将为国家科学基金会在国家减少地震灾害计划(NEHRP)中的作用做出贡献。项目数据将在自然灾害工程研究基础设施(NHERI)数据仓库(https://www.DesignSafe-ci.org).)存档并公开提供在地震危险性高的地区使用的中心支撑框架预计将通过支撑在压缩中屈曲和在拉伸中屈服来承受较大的非弹性变形。这些作用集中在支撑和节点板连接的中跨处，断裂通常发生在支撑中跨处。因此，纵向分段支撑方案侧重于修复跨中支撑，同时保留支撑的其他区域、连接和框架构件。主要研究目标包括：(1)开发分段支撑界面连接，通过在支撑铰链外引入额外的受控屈服机制来促进更换和提高抗震性能；(2)评估维修过程中保留的构件的抗震性能，包括剩余能力和基于性能的工程考虑；以及(3)生成实用的建模方法、性能验收标准、设计指南和其他结合现有钢结构建筑设计和评估规定的工程工具。对带分段支撑的框架进行了大规模的装配试验，以研究新的分段支撑设计以及其他框架构件的损伤累积效应。将使用经过实验验证的连续介质有限元分析来研究更广泛的分段支撑连接配置和地震荷载历史的非弹性响应，以指导分段支撑的设计和建模指南。该奖项反映了NSF的法定使命，并已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。

This Engineering Research Initiation (ERI) award will develop a new seismic design approach for steel braced frames using segmented braces configured for rapid post-earthquake repair. Buildings constructed in regions vulnerable to seismic hazards in the United States are designed to remain safe during large earthquakes, but structural components, such as diagonal braces, are designed to sustain damage as they dissipate seismic energy. This building damage may be severe and widespread in earthquake-affected communities, inhibiting the speed or possibility of post-earthquake occupancy, functionality, and repair. Steel braced frames are prevalent in existing building infrastructure across a broad range of uses, including hospitals, schools, offices, and industrial facilities, which are critical for post-earthquake shelter and care of people, distribution of goods, and economic productivity. The segmented bracing scheme will mitigate the impact of seismic damage in these common systems and enhance seismic resiliency by enabling relatively fast, low-cost replacement of the brace midspan segment such that most other system components can be safely retained. Experimental testing will investigate the seismic behavior of segmented braces applied to new construction and repair scenarios. An accompanying computational study will expand these findings to evaluate additional design parameters toward the development of design procedures and modeling recommendations suitable for engineering practice. The research activities will be incorporated into a laboratory experience course module in structural steel design and engage underrepresented groups in engineering through undergraduate research opportunities and outreach programs. This award will contribute to the National Science Foundation role in the National Earthquake Hazards Reduction Program (NEHRP). Project data will be archived and made publicly available in the Natural Hazards Engineering Research Infrastructure (NHERI) Data Depot (https://www.DesignSafe-ci.org). Concentrically braced frames used in regions with high seismic hazard are expected to sustain large inelastic deformations through brace buckling in compression and yielding in tension. These actions concentrate damage to the midspan of the brace and gusset plate connections, and fracture typically precipitates at the brace midspan. The longitudinally segmented brace scheme, therefore, focuses on repair of the brace midspan while retaining other regions of the brace, the connections, and the framing members. The major research objectives include: (1) development of segmented brace interface connections that facilitate replacement and improve seismic performance through the introduction of additional controlled yielding mechanisms outside the brace hinge; (2) evaluation of seismic behavior of components retained in repair, including residual capacity and performance-based engineering considerations; and (3) generation of practical modeling approaches, performance acceptance criteria, design guides, and other engineering tools contextualized in existing steel building design and evaluation provisions. Large-scale subassemblage testing of frames with segmented braces will be conducted to investigate the new segmented brace design and the effect of damage accumulation in other frame components. The inelastic response of a broader range of segmented brace connection configurations and seismic load histories will be studied using experimentally validated continuum finite-element analysis to inform design and modeling guidelines for segmented braces.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.