Probabilistic Seismic Demand Models and Life-Cycle Fragility Estimates for High-Rise Buildings

This paper presents a probabilistic framework for estimating the time-variant seismic fragility of high-rise buildings under carbonation-induced corrosion with a multiple damage model. A 42-story steel frame RC core tube (SFRCT) building was selected as a representative high-rise building to illustrate the proposed method. The main novelties of this study are that (1) a Bayesian updating method is used to determine the posterior probability distributions of the unknown parameters in the time-varying demand models of the maximum interstory drift and the residual drift at the top floor, (2) an analytical derivation method is used to compute the probability distribution of the corrosion initiation time in reinforcements, (3) the uncertainties associated with the corrosion initiation time and unknown parameters in demand models are incorporated into fragility estimates based on total probability theory, and (4) the elliptical copula and Archimedean copula are used to develop bivariate fragility estimates that consider the correlations among the limit states associated with maximum drifts and residual drifts, respectively. The results indicate that the seismic demand and fragility estimates of this high-rise building increase as the corrosion initiation time, which highlights the necessity of accounting for the uncertainty in the corrosion initiation time. In addition, the Gaussian copula and the Clayton copula (special cases of the elliptical copula and the Archimedean copula, respectively) produce similar joint probability distributions for the two-dimensional limit states; however, the Clayton copula can be used in a more general condition. The proposed methodology is applicable for evaluating the seismic life-cycle fragility of both existing and new high-rise buildings under multicriteria performance indicators.