Seismic Reliability Analysis of Elevated Liquid‐Storage Vessels

Abstract

The objective of this paper is to consider variations in the overall weight of structures and the resulting changes in fundamental periods, base shears, and spectral characteristics in seismic reliability analyses. A methodology is presented for assessing the annual failure probabilities of critical structural components, as a result of seismic excitation, for elevated liquid‐storage vessels, which typically have highly uncertain weight (mass) fluctuations throughout their service lives because of the changes in the amount of liquid stored in the vessel. A dis‐cretized‐mass mechanical system is used to model the forces induced by sloshing liquid. The seismic load input is obtained by combining the seismic hazard curve of the region and the site‐dependent dynamic amplification spectrum. The various sources of uncertainty are quantified in the analysis and a generalized limit‐state equation is derived for structural components. The analysis of a liquid‐containing elevated spherical vessel 65 ft (20 m) in diameter in the seismically active San Francisco Bay region is presented as an illustrative application of the method.