This paper presents a statistical analysis of structural fragility curves, focusing on both empirical and analytical approaches. Empirical fragility curves are developed using damage data from the 1995 Hyogo-ken Nanbu (Kobe) earthquake, while analytical curves are constructed based on nonlinear dynamic analysis. Two-parameter lognormal distribution functions are used to represent these curves, with parameters estimated using the maximum likelihood method. The paper also introduces methods for testing the goodness of fit of the fragility curves and estimating confidence intervals for the parameters. Additionally, it provides an analytical interpretation of randomness and uncertainty associated with the median value of the lognormal distribution. The study demonstrates the development of fragility curves for bridges in the Memphis area and discusses the creation of combined and composite fragility curves for categories of bridges. The results are validated through hypothesis testing and confidence interval estimation, and the paper concludes with a discussion on the implications of these findings for seismic risk assessment.This paper presents a statistical analysis of structural fragility curves, focusing on both empirical and analytical approaches. Empirical fragility curves are developed using damage data from the 1995 Hyogo-ken Nanbu (Kobe) earthquake, while analytical curves are constructed based on nonlinear dynamic analysis. Two-parameter lognormal distribution functions are used to represent these curves, with parameters estimated using the maximum likelihood method. The paper also introduces methods for testing the goodness of fit of the fragility curves and estimating confidence intervals for the parameters. Additionally, it provides an analytical interpretation of randomness and uncertainty associated with the median value of the lognormal distribution. The study demonstrates the development of fragility curves for bridges in the Memphis area and discusses the creation of combined and composite fragility curves for categories of bridges. The results are validated through hypothesis testing and confidence interval estimation, and the paper concludes with a discussion on the implications of these findings for seismic risk assessment.