Fragility assessment of liquid storage tanks under seismic loads by integration of two software packages

Abstract

Storage tanks are one of the most important structural components in an industrial complex. Damage to these structures due to seismic ground motions may cause leakage of hazardous materials, fires, or structural collapse. It is therefore important to analyze the seismic fragility of storage tanks, particularly when filled with liquid. When a storage tank is filled with liquid that oscillates during an earthquake, additional forces can affect the wall and roof owing to hydrodynamic pressure. For this reason, sophisticated structural analysis is required to take into account such a liquid-structure interaction in a seismic fragility assessment. In this study, a reliability analysis software package is integrated with commercial finite element analysis software to estimate the seismic fragility of liquid storage tanks. This integrated system enables the automatic exchange of the input and output of reliability and finite element analyses and the effective calculation of the probability of failure for a given limit state using the first order reliability method (FORM). This computational platform for finite element reliability analysis is applied to an example of a liquid storage tank, and the seismic fragility is successfully estimated in consideration of liquid-structure interaction.