This paper presents a statistical analysis of structural fragility curves.
Both empirical and analytical fragility curves are considered. The empirica
l fragility curves are developed utilizing bridge damage data obtained from
the 1995 Hyogo-ken Nanbu (Kobe) earthquake. The analytical fragility curve
s are constructed on the basis of the nonlinear dynamic analysis. Two-param
eter lognormal distribution functions are used to represent the fragility c
urves with the parameters estimated by the maximum likelihood method. This
paper also presents methods of testing the goodness of fit of the fragility
curves and estimating the confidence intervals of the two parameters (medi
an and log-standard deviation) of the distribution. An analytical interpret
ation of randomness and uncertainty associated with the median is provided.