NEESR-SG: Seismic Performance Assessment and Retrofit of Non-Ductile RC Frames with Infill Walls

摘要无筋砌体在建筑物中常用作内隔墙和外墙，一般被视为非结构构件。然而，与大多数非结构构件不同，它们在受到地震荷载时可以与边界框架产生强烈的相互作用，因此，对结构的侧向刚度和抗荷载能力有很大贡献。尽管研究已经跨越了几十年，但这些结构在强烈地震中的性能仍然是结构工程师和研究人员之间的主要争议。建议的研究的主要目的是开发合理和可靠的方法来评估砌体空心RC框架的抗震安全性和性能，并开发实用和有效的技术，这些结构的抗震加固使用传统的以及创新的材料。该项目将包括开发可靠的分析工具，从先进的计算模型到可用于工程实践的简单分析方法。该项目将利用NEES提供的大量计算资源和实验设施。分析方法和改造技术将首先进行验证，中型实验，在博尔德的科罗拉多大学的NEES快速混合测试设施进行。最终的概念验证测试将在3/4比例的三层钢筋混凝土框架上进行，使用位于圣地亚哥的加州大学的NEES大型高性能室外振动台。斯坦福大学将重点开发用于填充物改造的可喷射高性能纤维增强水泥基复合材料。这项工作将作为一个多机构，跨学科的努力，由一个多元化的研究团队，在专业实践，结构设计，结构测试，结构分析，计算力学和复合材料的专业知识。了解和评估填充墙非延性钢筋混凝土框架的抗震性能是结构工程中的一个难题。目前，还没有可靠的工程指南。分析工具，以评估复杂的框架填充相互作用和由此产生的故障机制需要建立在力学和合理的工程判断的基本原则。这比分析纯钢筋混凝土或砌体结构更具挑战性。这项研究将填补此类现有结构建模和性能评估方面的重大空白，这些结构经常出现在地震高风险地区，并制定有效的改造策略，以从系统角度禁止不期望的失效机制。该项目将涉及开发新的设计和评估技术，新材料和尖端的计算方法，这将是智力刺激。加州大学圣地亚哥分校、加州大学和斯坦福大学已经实施的教育和外展成功计划所提供的杠杆作用，以及将在NEES之外获得的额外资源，将加强NEESinc的共同教育和外展目标。利用合作实验室工具以及NEESgrid提供的远程呈现、数据存档和挖掘能力，拟议的循环研究和外联活动将确保及时向广大工程界和非工程界传播信息。该项目开发的先进计算模型将适用于许多新的和现有的结构，并提供基于三维模型的模拟能力，在可预见的未来可能取代物理实验。在NEESgrid支持的公共领域软件OpenSEES中实现高级计算模型将使整个地震工程界受益。所探讨的改造技术可能会为建筑业主节省大量资金，并提高大量现有结构的抗震安全性。简化的分析工具、设计和评估方法以及实验数据将为这类结构的下一代基于性能的抗震设计指南提供急需的信息和工具。该项目将设计、计算和实验融为一体，为未来地震工程师的性能工程培训提供了独特的经验。

ABSTRACTUnreinforced masonry in fills are frequently found as interior partitions and exterior walls in buildings, and are normally treated as non-structural elements. However, unlike most non-structural components, they can develop a strong interaction with the bounding frames when subject to earthquake loads and, therefore, contribute significantly to the lateral stiffness and load resistance of the structure. In spite of the research that have spanned several decades, the performance of these structures in a severe earthquake remains a major controversy among structural engineers and researchers today. The main aim of the proposed research is to develop rational and reliable methodologies for assessing the seismic safety and performance of masonry unfilled RC frames, and develop practical and effective techniques for the seismic retrofit of these structures using conventional as well as innovative materials. The project will include the development of reliable analysis tools that range from advanced computational models to simple analytical methods that can be used in engineering practice. The project will take advantage of the vast computational resources and experimental facilities provided by NEES. The analysis methods and retrofit techniques will be first validated with medium-scale experiments to beconducted with the NEES Fast Hybrid Test facility at the University of Colorado at Boulder. Final proof-of-concept tests will be conducted on a 3/4-scale three-story RC frame using the NEES Large High Performance Outdoor Shake Table at the University of California at San Diego. Stanford University will focus on the development of sprayable high-performance fiber-reinforced cement-based composites for infill retrofit. The work will be carried out as a multi-institutional, inter-disciplinary effort by a diverse research team with expertise in professional practice, structural design, structural testing, structural analysis, computational mechanics, and composite materials. Understanding and assessing the seismic performance of masonry-infilled non-ductile RC frames presents a most difficult problem in structural engineering. Currently, there are no reliable engineering guidelines for this. Analytical tools to evaluate the complicated frame-infill interaction and the resulting failure mechanisms need to be built on the fundamental principles of mechanics and sound engineering judgment. It is far more challenging than analyzing a pure RC or masonry structure. This research will fill a major gap in the modeling and performance assessment of this class of existing structures that can be frequently found in regions of high seismic risk and the development of effective retrofit strategies to prohibit the undesired failure mechanisms from a system perspective. The project will involve the development of new design and assessment techniques, new materials, and cutting-edge computational methods, which will be intellectually stimulating. The leverage provided by the successful programs on education and outreach that are already in place at UCSD, CU, and Stanford, and the additional resources that will be secured outside NEES will reinforce the common education and outreach goals of NEESinc. The proposed round-robin studies and outreach activities using the collaboratory tools, and the telepresence and data archiving and mining capabilities provided by the NEESgrid will assure timely dissemination of information to the broad engineering and lay communities. The advanced computational models developed in this project will be readily applicable to many new and existing structures and provide a 3-D model-based simulation capability that can potentially replace physical experiments in a foreseeable future. The implementation of the advanced computational models in a public-domain software, OpenSEES, which is supported by the NEESgrid, will benefit the earthquake engineering community at large. The retrofit techniques explored can potentially lead to significant savings by building owners and enhance the seismic safety of a large number of existing structures. The simplified analytical tools, design and assessment methodologies, andexperimental data will provide the much needed information and tools for the next-generationperformance-based seismic design guidelines on this class of structures. The integration of design, computation, and experimentation in this project provide a unique experience for the training of future earthquake engineers on performance-based engineering.