Analysis, Design and System-Level Performance of Repairable Precast Concrete Buckling-Restrained Braced Frames under Seismic Loads

以往地震造成的损失规模表明，建筑物需要能够在自然灾害发生后迅速恢复其基本功能。这个概念称为功能恢复。该项目将通过创建和检查具有新型非专有斜撑的可修复预制混凝土防屈曲支撑（BRB）框架结构，为国家的功能恢复目标做出贡献。新支架具有低成本特点，可以在地震后进行实际更换。该项目将产生有关该建筑系统的抗震设计和性能的基础知识。数据将通过数值分析、孤立支撑及其连接的测试以及对三层建筑的抗震性能和修复的最终测试而生成，该建筑使用由加州大学圣地亚哥分校运营的六自由度大型高性能户外振动台，作为 NSF 资助的自然灾害工程研究基础设施 (NHERI) 的一部分。该项目将强调多样性和包容性，将让来自弱势群体的本科生参与教育和指导计划，并将为大学预科生创建工程学习模块。预制行业合作伙伴将提供样本和技术指导，强调该项目注重行业首选的结构细节以供实际验收。将通过预测振动台上的建筑响应的竞赛来实现更广泛的工程界的参与。该项目生成的数据将被存档并在 NHERI 数据仓库 (https://www.DesignSafe-CI.org) 中公开提供。该奖项将有助于 NSF 在国家地震减灾计划 (NEHRP) 中发挥作用。目前美国还没有关于预制 BRB 框架结构抗震性能的全面研究。该项目将通过以下方式填补这一研究空白：1）设计和表征新型可更换混凝土支撑的行为，2）评估多层支撑框架的设计和建模，以及3）评估建筑物内这些框架的抗震行为。新的支撑将通过结构高效的细节实现延性和稳定的性能，其中包括穿过支撑端部间隙接头的消能钢筋，并与螺纹耦合器和加大尺寸的钢筋拼接，以最大限度地减少梁和柱构件的损坏。这种螺纹间隙接头连接将允许在地震后用现浇混凝土支撑替换损坏的预制支撑。将开发详细的数值模型并进行实验验证，以预测可能导致支撑过早失效的三维应力梯度和损坏条件，并评估多层支撑框架的有效设计基础模型。建模和设计方法将通过对六自由度振动台上的预制支撑框架进行首次系统级测试来验证。这些最终测试将展示支撑框架、其连接以及支撑更换在多向需求下的性能。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

The scale of losses from previous earthquakes has demonstrated the need for buildings that can rapidly restore their essential functions after a natural disaster. This concept is called functional recovery. This project will contribute to the nation’s functional recovery objectives by creating and examining a repairable precast concrete buckling-restrained braced (BRB) frame structure with a new type of non-proprietary diagonal brace. The new brace will have low-cost features that permit practical replacement after an earthquake. This project will generate fundamental knowledge on the seismic design and performance of this building system. Data will be generated from numerical analyses, testing of isolated braces and their connections, and culminating tests on the seismic performance and repair of a three-story building utilizing the six-degree-of-freedom Large High-Performance Outdoor Shake Table operated by the University of California, San Diego, as part of the NSF-funded Natural Hazards Engineering Research Infrastructure (NHERI). The project will emphasize diversity and inclusion, will engage undergraduates from underrepresented groups in education and mentoring programs, and will create engineering learning modules for pre-college students. Precast industry partners will provide specimens and technical guidance emphasizing the project’s focus on industry-preferred structural details for practical acceptance. Engagement with the broader engineering community will be achieved through a competition to predict the building response on the shake table. Data generated from this project will be archived and made publicly available in the NHERI Data Depot (https://www.DesignSafe-CI.org). This award will contribute to NSF's role in the National Earthquake Hazards Reduction Program (NEHRP). There is currently no comprehensive U.S.-based research on the seismic performance of precast BRB frame structures. This project will fill this research gap by 1) designing and characterizing the behavior of a novel, replaceable concrete brace, 2) evaluating the design and modeling of multi-story braced frames, and 3) evaluating the seismic behavior of these frames within a building. The new brace will achieve ductile and stable behavior by structurally efficient details incorporating energy-dissipating reinforcing bars crossing gap-joints at the brace ends and spliced with threaded couplers and upsized bars to minimize damage in the beam and column members. This threaded gap-joint connection will permit damaged precast braces to be replaced with cast-in-place concrete braces after an earthquake. Detailed numerical models will be developed and experimentally validated to predict three-dimensional stress gradients and damage conditions that could lead to premature failure of the brace, and to evaluate efficient design-basis models for multi-story braced frames. The modeling and design methods will be validated with the first system-level testing of a precast braced frame building on the six-degree-of-freedom shake table. These culminating tests will demonstrate the performance of the braced frames, their connections, and brace replacement under multi-directional demands.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.