Performance-based seismic evaluation is usually done by considering simplified models for the liquid storage tanks therefore, it is important to validate those simplified models before conducting such evaluation. The purpose of this study is to compare the seismic response results of the FSI (fluid-structure interaction) model and the simplified models for the cylindrical liquid storage tanks and to verify the applicability of the simplified models for estimating failure probability. Seismic analyses were carried out for two types of storage tanks with different aspect ratios (H/D) of 0.45 and 0.86. FSI model represents detailed 3D fluid-structure interaction model and simplified models are modeled as cantilever mass-spring model, frame type mass-spring model and shell type mass-spring model, considering impulsive and convective components. Seismic analyses were performed with modal analysis followed by time history analysis. Analysis results from all the models were verified by comparing with the results calculated by the code and literature. The results from simplified models show good agreement with the ones from detailed FSI model and calculated results from code and literature, confirming that all three types of simplified models are very valid for conducting failure probability analysis of the cylindrical liquid storage tanks.

ABSTRACT
 1. Introduction
 2. Finite Element Model Formulation
  2.1 FSI model formulation
  2.2 Simplified model formulation
 3. Numerical studies
  3.1 Modal analysis
  3.2 Time history analysis
 4. Conclusions
 Nomenclature
 REFERENCES

• Nabin Raj Chaulagain(Ph.D. candidate, Department of Civil and Environmental Engineering, University of Ulsan)
• Sun Chang Ho(Department of Civil and Environmental Engineering, University of Ulsan)
• Kim Ick Hyun(Department of Civil and Environmental Engineering, University of Ulsan) Corresponding author