Seismic Capacity and Failure Modes of Flat‐Bottom Vertical Tanks

Abstract

Flat‐bottom vertical storage tanks are vital components in nuclear power plant safety systems. Potential failure modes of such tanks due to earthquake ground motion and current methods available to evaluate the seismic capacities of tanks against these failure modes are identified. Substantial data on tank failure modes, seismic response, and seismic capacity are cited. These data are distinguished into three types: (1) Earthquake experience data from the performance of tanks in actual earthquakes; (2) test data from laboratory specimens or tanks in the field; and (3) analytical data from theoretical derivations or analyses. It is concluded that these data provide clear guidance on probable failure modes. Limited analyses have been performed to benchmark current seismic evaluation methods for tanks against test and earthquake experience data. In general, these studies demonstrate that current analytical evaluation methods provide sufficiently accurate means to predict the seismic capacities of flat‐bottom tanks at nuclear power plants.