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

Cornell University, Ithaca NY

Investigators

Abstract

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.