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

以往地震造成的巨大损失表明，需要在自然灾害发生后迅速恢复其基本功能的建筑。这个概念被称为功能恢复。该项目将通过创建和检查一种可修复的预制混凝土抗屈曲支撑（BRB）框架结构，以及一种新型的非专有对角支撑，为国家的功能恢复目标做出贡献。新的支撑具有低成本的特点，可以在地震后进行实际更换。这个项目将产生关于这个建筑系统的抗震设计和性能的基本知识。数据将从数值分析、隔离支撑及其连接的测试，以及利用加州大学圣地亚哥分校运营的六自由度大型高性能室外振动台对一栋三层建筑的抗震性能和修复进行的最终测试中产生，该测试是美国国家科学基金会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，将让来自代表性不足群体的本科生参与教育和指导项目，并将为大学预科学生创建工程学习模块。预制行业合作伙伴将提供样品和技术指导，强调项目的重点是行业首选的结构细节，以便实际验收。通过预测建筑物在振动台上的反应的竞赛，将与更广泛的工程界进行接触。该项目产生的数据将存档并在NHERI数据仓库（https://www.DesignSafe-CI.org）中公开提供。该奖项将有助于NSF在国家减少地震灾害计划（NEHRP）中的作用。美国目前还没有对预制BRB框架结构抗震性能进行全面的研究。本项目将填补这一研究空白：1)设计和表征一种新颖的、可替换的混凝土支撑的行为，2)评估多层支撑框架的设计和建模，以及3)评估这些框架在建筑物内的抗震行为。新型支撑将通过高效的结构细节实现延展性和稳定性，这些细节包括在支撑端部的缝隙接缝处安装耗能钢筋，并与螺纹耦合器和增大的钢筋拼接在一起，以最大限度地减少梁和柱构件的损坏。这种螺纹缝隙连接将允许损坏的预制支撑在地震后用现浇混凝土支撑代替。详细的数值模型将被开发和实验验证，以预测三维应力梯度和可能导致支撑过早破坏的损伤条件，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在六自由度振动台上对预制支撑框架建筑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的性能，它们的连接，以及在多向要求下的支撑更换。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识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.