Seismic Fragility Curves for On-Grade Steel Tanks

The study reported herein attempts to characterize the seismic behavior of cylindrical on-grade, steel liquid storage tanks subject to the ground shaking hazard. The behavior is quantified by fragility curves that resulted from an analysis of the reported performance of over 400 tanks in nine separate earthquake events. The damage states used herein to characterize damage (i.e., slight, moderate, etc.) are intended to mirror damage state descriptions in the HAZUS Earthquake Loss Estimation Methodology. The amount of ground shaking is quantified by the peak ground acceleration (PGA) at the site. The influence of the tank's height to diameter ratio, H/D, as well as the relative amount of stored contents, % Full, are investigated and were found to have had a significant effect upon tank seismic performance. Finally, the fragility curves developed herein are compared to corresponding relations currently available in the technical literature.