NEESR-II: Sidesway Collapse of Deteriorating Structural Systems

NEESR-II：恶化结构系统的侧向倒塌

• 批准号: 0421551
• 负责人: Helmut Krawinkler
• 金额: $ 44.93万
• 依托单位: Stanford University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-10-01 至 2008-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0421551&HistoricalAwards=false
• 关键词: NEESR; II; Sidesway; Collapse; Deteriorating

Understanding, predicting, and preventing collapse have always been major objectives of earthquake engineering. Collapse is the main source of injuries and loss of lives. Thus, it constitutes an engineering limit state that needs to be predicted in order to evaluate, in a probabilistic format, the life safety performance level, which is of primary societal concern. In the context of earthquake risk management, a process is needed that permits a rigorous assessment of the probability of collapse to make informed decisions in the best interest of society. In the context of earthquake resistant design, this process needs to be simplified so that the engineering profession can use engineering techniques, which are based on parameters such as strength, stiffness, and ductility (deformability), to derive structural properties that comply with specified targets for a required level of collapse safety, or a tolerable probability of collapse. This project will address both contexts. It will provide a methodology and reliable data for predicting a critical mode of collapse, namely that associated with sidesway instability in which an individual story (or a series of stories) displaces sufficiently so that the second order P-delta effects fully offset the first order story shear resistance and dynamic instability occurs, i.e., the structural system loses its gravity load resistance. Prediction of this mode of collapse is a challenging problem because structural components will deteriorate in strength and stiffness before the collapse limit state is reached, and great uncertainties are associated with the description of the seismic input and of the parameters that control the response of structures close to collapse. The methodology will be based on a combination of analytical and experimental simulations, with the former being carried out at Stanford University and the main effort of the latter, a shaking table collapse test of a model of a steel structure, being carried out at the NEES facility at the University at Buffalo. The outcomes of the proposed research will be (a) a methodology for predicting sidesway collapse of deteriorating structural systems, (b) an extensive database on deterioration properties of structural steel and reinforced concrete components, including uncertainty measures accounting for modeling and material uncertainties, (c) incorporation of component deterioration models in the OpenSees platform, (d) documentation of a comprehensive collapse experiment with data that covers the range of response of a 5-story steel frame structure from elastic behavior to incipient collapse, (e) a methodology for computing the probability of sidesway collapse that accounts for hazard, ground motion, and structural (material, modeling) uncertainties, and (f) engineering recommendations for design for collapse safety. Intellectural Merit. The proposed research will lead to seminal advances in understanding and predicting sidesway collapse of structures subjected to severe earthquakes. The major challenges are to account for deterioration in structural behavior in combination with P-delta effect, and for the uncertainties inherent in ground motion description and in modeling the behavior of the components that control the dynamic response at large inelastic deformations (or at small deformations in the case of brittle elements). These challenges imply extensive modeling efforts at the component and structure level and the incorporation of reliability concepts in assessing collapse safety of structures. Another major challenge will be the planning and execution of a shaking table collapse experiment, whose main purpose is to demonstrate that collapse prediction indeed is feasible. The research involves an integrated approach of physical simulations at a NEES site shaking table and computational simulations on the OpenSees platform, while fully utilizing the simulation, visualization, and collaboration tools of the NEESgrid. Broader Impacts on Earthquake Engineering Research and Practice. The research is motivated by professional needs to provide adequate and consistent collapse safety in new designs and to assess the collapse hazard of existing structures. These needs require the filling of knowledge gaps that exist in regard to data and tools and the understanding of collapse phenomena. The impact of the proposed work on research and practice will be the development of databases, advanced deterioration models, and computational tools that will make it feasible to predict the collapse safety of complex structures and will permit more rational allocation of resources in the context of performance-based seismic risk management. The impact will be felt in the academic environment in teaching and research, in engineering design offices, and in organizations concerned with risk management.

认识、预测和预防倒塌一直是地震工程学的主要目标。 倒塌是造成伤亡的主要原因。 因此，它构成了一个需要预测的工程极限状态，以便以概率形式评估生命安全性能水平，这是主要的社会问题。 在地震风险管理方面，需要有一个程序，允许对倒塌的可能性进行严格评估，以便做出符合社会最佳利益的明智决定。 在抗震设计的背景下，这一过程需要简化，以便工程专业人员可以使用基于强度、刚度和延展性（变形性）等参数的工程技术来推导出符合指定目标的结构特性。倒塌安全水平或可容忍的倒塌概率。本项目将处理这两种情况。 它将为预测临界倒塌模式提供一种方法和可靠的数据，即与侧向不稳定性有关的模式，在这种模式下，单个楼层（或一系列楼层）发生足够的位移，使得二阶P-δ效应完全抵消一阶楼层剪切阻力，并发生动力不稳定性，即， 结构系统失去其重力负载抵抗力。 预测这种模式的崩溃是一个具有挑战性的问题，因为结构部件将在倒塌极限状态之前，在强度和刚度恶化，和很大的不确定性与地震输入的描述和控制接近崩溃的结构的响应的参数。该方法将以分析模拟和实验模拟相结合为基础，前者在斯坦福大学进行，后者的主要工作是在布法罗大学的NEES设施进行钢结构模型的振动台倒塌试验。 拟议研究的成果将是：（a）预测恶化结构系统侧向倒塌的方法，（B）关于结构钢和钢筋混凝土构件恶化特性的广泛数据库，包括考虑建模和材料不确定性的不确定性措施，（c）在OpenSees平台中纳入组件退化模型，（d）记录全面倒塌实验的数据，涵盖5层钢框架结构从弹性行为到初始倒塌的反应范围，（e）计算侧向坍塌概率的方法，该方法考虑了灾害、地面运动和结构（材料、模型）的不确定性，以及（f）坍塌安全设计的工程建议。智力上的优点。 拟议的研究将导致在理解和预测遭受严重地震的结构侧向倒塌方面取得重大进展。 主要的挑战是考虑结构性能的恶化与P-δ效应的结合，以及地面运动描述中固有的不确定性和控制大非弹性变形（或脆性元件情况下的小变形）下动态响应的组件行为建模中的不确定性。 这些挑战意味着广泛的建模工作，在组件和结构的水平，并纳入可靠性的概念，在评估结构的倒塌安全。 另一个主要的挑战将是计划和执行振动台倒塌实验，其主要目的是证明倒塌预测确实是可行的。 该研究涉及NEES现场振动台物理模拟和OpenSees平台计算模拟的综合方法，同时充分利用NEESgrid的模拟，可视化和协作工具。对地震工程研究和实践的广泛影响。 这项研究的动机是专业的需要，以提供足够的和一致的倒塌安全在新的设计，并评估现有结构的倒塌危险。 这些需求要求填补在数据和工具方面存在的知识空白，以及对坍塌现象的理解。 拟议的工作对研究和实践的影响将是数据库的发展，先进的恶化模型，和计算工具，这将使它可行的预测复杂结构的倒塌安全，并允许更合理的资源分配的情况下，基于性能的地震风险管理。 这种影响将体现在教学和研究的学术环境、工程设计办公室以及与风险管理有关的组织中。