Optimal Structural System Design for Catastrophic Unforeseen Events

9/11事件表明，需要考虑一个结构建筑安全的决策框架，以应对不可预见的事件。本研究计画将提供一个架构，以供在不可预见的灾难性事件下，进行建筑结构安全性的决策与约束最佳化。不可预见的事件（即，恐怖主义破坏、腐蚀构件）的重现期惊人地短，并打破了环境荷载与结构失效概率（Pf）之间的传统联系。目前的设计，只使用组件明智的可靠性，忽视冗余，缺乏一个正式的决策框架，是不够的。通过扩展最近的想法，在结构灵敏度，冗余度，概率地震工程，我们提出了一个表征Pf在不可预见的事件，通过两个随机变量：强度测量（IM）和工程需求参数（EDP）。IM描述了不可预见损坏的程度和相关性。EDP为给定IM提供到Pf的链接。还将考虑使用冗余索引（R）来提供Pf的粗略但计算上廉价的指示符。使用Pf和/或随机变量IM，EDP和R，我们将探索低概率，高风险，灾难性事件的决策。这些事件迫使我们重新考虑冯·诺依曼·摩根斯特伦效用理论的适用性。最近的研究在巨灾风险保险将被用来开发一个适当的目标函数优化建筑物的安全。无论人们认为世贸中心在9/11袭击期间的行为是设计上的成功，因为很多人都能够安全地到达，还是设计失败，在所有建筑物倒塌之后-一个可能在由此产生的讨论中被忽视的问题是，建筑物的行为不是我们的“建筑规范”或我们目前的设计方法的直接结果。拟议的工作结合了结构灵敏度，冗余，概率地震工程，不确定性下的优化和灾难性风险保险的新发现。这项研究将导致更好的决策，在建筑物的设计，并确保更高水平的建筑结构安全，在现实的经济限制，考虑灾难性破坏事件的可能性。

The events of 9/11 demonstrate the need for consideration of a decision-making framework for structural building safety in response to unforeseen events. This research project will provide such a framework for decision-making and constrained optimization of building structural safety under unforeseen catastrophic events. Unforeseen events (i.e., terrorism damage, corroded members) occur with a surprisingly short return period and break the traditional link between environmental loads and the probability of structural failure (Pf). Current design, using only component-wise reliability, ignoring redundancy, and lacking a formal decision-making framework, is inadequate. By extending recent ideas in structural sensitivity, redundancy, and probabilistic earthquake engineering we propose a characterization for Pf in unforeseen events through two stochastic variables: an intensity measure (IM) and an engineering demand parameter (EDP). The IM describes the magnitude and correlation of the unforeseen damage. The EDP provides a link to Pf for a given IM. The use of a redundancy index (R) to provide a coarse, but computationally cheap indicator of Pf, will also be considered. Using Pf and/or the stochastic variables IM, EDP and R we will explore decision-making for low-probability, high-risk, catastrophic events. Such events force us to reconsider the applicability of the von Neumann Morgenstren utility theory. Recent research in catastrophic risk insurance will be utilized to develop an appropriate objective function for optimization of building safety. Whether one views the behavior of the World Trade Center during the attacks of 9/11 as a design success, because so many people were able to get to safety, or a design failure, after all the buildings collapsed - one issue that may have been lost in the resulting discussion is that the building's behavior is not a direct result of our "building codes" nor our current design methodologies. The proposed work combines new findings in structural sensitivity, redundancy, probabilistic earthquake engineering, optimization under uncertainty and catastrophic risk insurance. This research will lead to better decision-making in the design of buildings and insure a higher level of building structural safety, within realistic economic constraints, when considering the possibility of catastrophic damage events.