STATISTICAL ANALYSIS OF FRAGILITY CURVES

This report presents methods of bridge fragility curve development on the basis of statistical analysis. Both empirical and analytical fragility curves are considered. The empirical fragility curves are developed utilizing bridge damage data obtained from past earthquakes, particularly the 1994 Northridge and 1995 Hyogo-ken Nanbu (Kobe) earthquakes. Analytical fragility curves are constructed for typical bridges in the Memphis, Tennessee area utilizing nonlinear dynamic analysis. Two-parameter lognormal distribution functions are used to represent the fragility curves. These two parameters (referred to as fragility parameters) are estimated by two distinct methods. The first method is more traditional and uses the maximum likelihood procedure treating each event of bridge damage as a realization from a Bernoulli experiment. The second method is unique in that it permits simultaneous estimation of the fragility parameters of the family of fragility curves, each representing a particular state of damage, associated with a population of bridges. The method still utilizes the maximum likelihood procedure, however, each event of bridge damage is treated as a realization from a multi-outcome Bernoulli type experiment. These two methods of parameter estimation are used for each of the populations of bridges inspected for damage after the Northridge and Kobe earthquakes and with numerically simulated damage for the population of typical Memphis area bridges. Corresponding to these two methods of estimation, this report introduces statistical procedures for testing goodness of fit of the fragility curves and of estimating the confidence intervals of the fragility parameters. Some preliminary evaluations are made on the significance of the fragility curves developed as a function of ground intensity measures other than PGA. Furthermore, applications of fragility curves in the seismic performance estimation of expressway network systems are demonstrated. Exploratory research was performed to compare the empirical and analytical fragility curves developed in the major part of this report with those constructed utilizing the nonlinear static method currently promoted by the profession in conjunction with performance-based structural design. The conceptual and theoretical treatment discussed herein is believed to provide a theoretical basis and practical analytical tools for the development of fragility curves, and their application in the assessment of seismic performance of expressway network systems.

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  • Corporate Authors:

    Multidisciplinary Center for Earthquake Engineering Research

    State University of New York, 107 Red Jacket Quadrangle, P.O. Box 610025
    Buffalo, NY  United States  14261-0025

    University of Southern California, Los Angeles

    Department of Civil and Environmental Engineering
    3620 South Vermont Avenue
    Los Angeles, CA  United States  90089-2531

    Federal Highway Administration

    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590
  • Authors:
    • Shinozuka, M
    • Feng, M Q
    • Kim, H Y
    • Uzawa, T
    • Ueda, T
  • Publication Date: 2003-6-16

Language

  • English

Media Info

Subject/Index Terms

Filing Info

  • Accession Number: 00962912
  • Record Type: Publication
  • Report/Paper Numbers: Technical Report,, MCEER-03-0002
  • Contract Numbers: DTFH61-92-C-00106
  • Files: TRIS, USDOT
  • Created Date: Sep 25 2003 12:00AM