A STUDY OF FORMULARIZATION OF UPLIFT BEHAVIOR AT THE BOTTOM PLATE OF LARGE LNG STORAGE TANKS DURING EARTHQUAKE

摘要

In recent years, it has been found that seismic demand tends to be higher for LNG storage tanks and it requires detail estimations about the tank uplift. Generally FE analysis is performed for this aim, since the most of present design standards do not specify the design formula to calculate the stress of the bottom plate. In the case of establishing the bottom plate model with the uplift, several properties have to be considered, such as tank dimension and plate thickness, magnitude and distribution of dynamic liquid pressure that is affected by width and height of the uplift, elasticity of the bottom insulation, and bulging displacement of the tank sidewall. As an another approach for detail estimations including these properties, this study presents the mathematical solution of the bottom plate for estimating uplift height and stress distribution based on a theory of elastic bearing beam. To increase accuracy but maintain practicality, the thin cylindrical theory is also coupled to the bottom plate model for considering the influence of bulging displacement of the tank sidewall on the bottom plate. From the parameter study by the proposed model, it is found that the bulging displacement of the sidewall has significant effect to the uplift height of the bottom plate.