EAGER: A New Perspective on Seismic Intensity Measures and Fragility Analysis

这个探索性研究（EAGER）项目将研究一种评估结构系统抗震性能的新方法，该方法将提供准确的性能估计，而不考虑结构系统的复杂性，并将为基于性能的地震工程提供有效的工具。该方法将为基于性能的地震工程定义一个新的范例，这在当前实践中构成了一个重大的方向性变化。该项目将研究：(1)适合于基于性能的地震工程的脆弱性分析的新范式，(2)构建与结构类型/需求参数无关的低方差脆弱性的方法，以及(3)评估受部分已知随机输入影响的动态系统性能的一般方法。地震易损性分析的概率模型和方法也可以扩展到评估其他自然灾害对建筑环境的影响，如风、龙卷风和海啸波。这个项目的总体目标是：(1)表明以强度测量（IMs）函数定义的脆弱性可能有很大的方差，因此对结构体系抗震性能的预测可能是不准确的；(2)研究地震输入的替代特征，使用地震地面加速过程的物理参数，并利用它们来定义一类新的脆弱性；(3)通过数值算例和理论分析论证了脆弱性的优越性。为了实现这些目标，该项目将使用随机振动，随机向量的copula模型的性质，以及极值理论的概念。这项研究的结果将是一个可靠的方法来估计结构系统的地震脆弱性，可以直接扩展到自然灾害和其他灾害。脆弱性分析和基于性能的地震工程的基石IMs将不会被使用。易损性将被定义为地震地面加速度物理参数的函数，例如矩量级、震源距离和土壤类型。脆弱性的实施及其在基于性能的地震工程中的可行性将通过涉及现实结构体系和地震危险的例子来证明。

This EArly-concept Grant for Exploratory Research (EAGER) project will investigate a novel methodology for evaluating the seismic performance of structural systems, which will deliver accurate estimates of performance irrespective of the complexity of the structural system, and will provide efficient tools for performance-based earthquake engineering. The methodology will define a new paradigm for performance-based earthquake engineering, which constitutes a significant directional change in current practice. The project will investigate: (1) a novel paradigm for fragility analysis adequate for performance-based earthquake engineering, (2) a method for constructing fragilities that have low variance irrespective of structural types/demand parameters, and (3) a general methodology for assessing the performance of dynamic systems subjected to partially known random inputs. The probabilistic models and methods for seismic fragility analysis also can be extended to assess effects on the built environment of other natural hazards, such as wind, tornadoes, and tsunami waves. The overall objectives of this project are to: (1) show that fragilities defined as functions of intensity measures (IMs) are likely to have large variances so that predictions of the seismic performance of structural systems can be inaccurate, (2) investigate alternative characterizations of the seismic input, using physical parameters of the seismic ground acceleration process, and employ them to define a novel class of fragilities, and (3) demonstrate the superiority of the fragilities by numerical examples and theoretical considerations. To achieve these objectives, the project will use random vibration, properties of copula models for random vectors, and concepts of extreme value theory. The output of this research will be a robust methodology for estimating seismic fragilities of structural systems that can be extended directly to natural and other hazards. IMs, the cornerstone of fragility analysis and performance-based earthquake engineering, will not be used. Fragilities will be defined as functions of physical parameters of seismic ground acceleration, e.g., moment magnitude, site to source distance, and soil type. The implementation of the fragilities and their feasibility for performance-based earthquake engineering will be demonstrated by examples involving realistic structural systems and seismic hazards.