Seismic Retrofit of Horizontal Lateral Force Resisting Systems in Buildings

该项目旨在提高对混凝土建筑物在地震荷载作用下水平侧向力抵抗体系的脆弱性的了解，并通过有针对性的加固和增强延性的模式，为纤维增强聚合物加固创造新的方法。水平侧向力抵抗系统由横隔板、弦杆和集热器组成，在翻新期间、在楼板中切入穿透时或在旧建筑中发现面内荷载路径、强度或延性方面的不足时，通常需要进行翻新。与传统的混凝土和钢材加固相比，外贴纤维增强聚合物更易于安装，并且不会增加建筑重量，因此越来越多地被用于提高横隔板的性能。然而，由于其相对较大的尺寸和其他因素，很少有人研究如何最好地使用外部粘结复合材料来改进不足的水平侧力抵抗系统。本研究将开发的新的翻新方法对于提高基础设施对地震等自然灾害的复原力以及通过适应性再利用而不是拆除和重建来改善基础设施的可持续性具有重要意义。该项目将为研究生和本科生提供培训，并将策划一个社交媒体微博，以刺激和激励在科学和工程领域未被充分代表的个人。该奖项将为国家科学基金会(NSF)在国家减少地震灾害计划(NEHRP)中的作用做出贡献。该项目的数据将被存档并在美国国家科学基金会支持的自然灾害工程研究基础设施(NHERI)数据仓库(http://www.designsafe-ci.org).)中公开提供该项目的目标是(1)阐明不受垂直建筑轴线限制的三角定向加固的有效模式，(2)通过新的混凝土约束技术增强楼板中轴向构件的循环性能，以及(3)建立水平和垂直系统之间的力传递，这种传递可能不会发生在垂直线上。新的基础知识将释放与非正交单元、更有效的力流模式和优化相关的机会，这些优化将用于推进膜片的新设计和分析方法。研究计划包括综合的计算和实验任务，包括：(1)使用拓扑优化和支撑和系杆概念对一组原型建筑进行有针对性的加固方法，(2)大规模实验研究以调查现有和翻新楼板的行为，(3)验证可以模拟复杂混凝土楼板系统性能的计算模型，(4)使用计算模型评估改造方法，以及(5)综合可应用于实际横隔板的概括性设计策略。通过向学术界、执业工程师和适当的建筑规范委员会广泛传播研究结果，将扩大研究的影响。该奖项反映了NSF的法定使命，并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 project aims to advance understanding of the vulnerabilities in the horizontal lateral force resisting system of concrete buildings subject to seismic loads and create new approaches for fiber reinforced polymer retrofit through patterns of targeted strengthening and enhanced ductility. The horizontal lateral force resisting system, consisting of the diaphragm, chords, and collectors, often requires retrofit during renovations, when penetrations are cut in the slab, or in older buildings when deficiencies in the in-plane load path, strength, or ductility are discovered. Externally bonded fiber reinforced polymers are increasingly being used to improve diaphragm performance because they are easier to install and do not increase the building weight as compared with conventional concrete and steel strengthening. However, because of their relatively large size and other factors, little research has been conducted to understand how externally bonded composites can be best used to retrofit deficient horizontal lateral force resisting systems. The new retrofit approaches to be developed in this research are important for their potential to increase infrastructure resilience to natural hazards such as earthquakes, as well as improving infrastructure sustainability through adaptive reuse rather than demolition and reconstruction. This project will provide training for graduate and undergraduate students and will curate a social media microblog to excite and inspire individuals underrepresented in science and engineering. This award will contribute to the National Science Foundation (NSF) role in the National Earthquake Hazards Reduction Program (NEHRP). Data from the project will be archived and made publicly available in the NSF-supported Natural Hazards Engineering Research Infrastructure (NHERI) Data Depot (http://www.designsafe-ci.org). The project objectives are to (1) elucidate efficient patterns of triangulated targeted strengthening that are not constrained to orthogonal building axes, (2) enhance cyclic behavior of axial elements in the floor through new concrete confinement techniques, and (3) establish force transfer between the horizontal and vertical systems that may not occur along orthogonal lines. The new fundamental knowledge will unlock opportunities related to nonorthogonal elements, more efficient force flow patterns, and optimization that will be used to advance new design and analysis approaches for diaphragms. The research plan consists of integrated computational and experimental tasks that include: (1) using topology optimization and strut and tie concepts on a set of archetype buildings to develop targeted strengthening approaches, (2) a large-scale experimental study to investigate behavior of existing and retrofitted floors, (3) validation of computational models that can capture the behavior of complex concrete floor systems with and without composite retrofitting, (4) evaluating retrofit approaches using computational models, and (5) synthesizing generalizable design strategies that can be applied to practical diaphragms. The research impact will be broadened through wide dissemination of the research results to the academic community, practicing engineers, and appropriate building code committees.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.