Optimal Structural System Design for Catastrophic Unforeseen Events

9/11事件表明，有必要考虑结构建筑安全决策框架，以应对不可预见的事件。本研究项目将为不可预见的灾难性事件下的建筑结构安全决策和约束优化提供这样一个框架。不可预见的事件（如恐怖主义破坏、构件腐蚀）发生的回复期短得惊人，打破了环境荷载与结构破坏概率（Pf）之间的传统联系。目前的设计，只使用组件的可靠性，忽略冗余，缺乏正式的决策框架，是不够的。通过扩展结构敏感性、冗余度和概率地震工程方面的最新思想，我们提出了通过两个随机变量（强度测量（IM）和工程需求参数（EDP））表征不可预见事件中Pf的特征。IM描述了不可预见损害的大小和相关性。EDP为给定的IM提供到Pf的链接。还将考虑使用冗余指数(R)来提供一个粗略但计算成本较低的Pf指标。使用Pf和/或随机变量IM， EDP和R，我们将探讨低概率，高风险，灾难性事件的决策。这些事件迫使我们重新考虑冯·诺伊曼·摩根斯特伦效用理论的适用性。本文将利用巨灾保险的最新研究成果，为建筑安全优化制定合适的目标函数。无论是将世贸中心在9/11袭击期间的行为视为设计上的成功，因为很多人能够安全到达，还是将其视为所有建筑物倒塌后的设计失败，在讨论中可能忽略的一个问题是，建筑物的行为并不是我们的“建筑规范”或我们当前的设计方法的直接结果。提出的工作结合了结构敏感性，冗余，概率地震工程，不确定性下的优化和巨灾风险保险的新发现。这项研究将导致更好的决策，在建筑设计和确保更高水平的建筑结构安全，在现实的经济约束下，当考虑到灾难性的破坏事件的可能性。

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.