Rainfall in Korea is characterized by concentration of rainfall in summer, so a considerable number of water storage facilities (dams, weirs, reservoirs, etc.) have been constructed. In addition, due to the fact that the population is concentrated in large cities, the number of water and wastewater treatment facilities has been increasing, and the gradually growing demand on natural gas, a clean fuel, also is increasing the number of Liquefied Natural Gas(LNG) storage facilities. Moreover, there is a growing concern that Korea is no longer safe for earthquakes because an earthquake has occurred recently in Gyeongju. Therefore, it is necessary to pay attention to the safety of these various fluid storage structures against earthquakes.
When a seismic load is applied to the fluid storage structure, hydrostatic pressure generated by the interaction of the structure and the internal fluid in addition to the inertial force additionally acts on the structure. However, there is a practical limit to proceed with precise dynamic analysis taking into account fluid-structure interaction effects in the design stage. Currently, domestic and international design criteria for seismic design of fluid storage structures mostly use the concentrated mass model by Houser or additional mass model by Westergaard. However, the concentrated mass model proposed by Housner has the problem that the aspect ratio (h/B) of the fluid storage structure can not be considered. The additional mass model proposed by Westergaard also differs from the actual hydrostatic pressure because the structure is assumed to be a rigid body.
An additional mass function that can estimate the effect of hydrostatic pressure acting on a structure by the additional mass method is proposed in this study. Shaking table experiments and structural analysis for model tanks were conducted for this purpose. The shaking table test for model tanks was conducted in an acrylic tank filled with 25% and 40% water. The vibration test of this acrylic model tank was reproduced by FEM analysis using SPH technique. The sloshing profile of the free surface of the model water tank was compared to evaluate the accuracy of the FEM analysis. In particular, the comparison of the shape of the free surface at the time of maximum slushing showed that the FEM analysis using the SPH technique predicts the slushing behavior of the fluid very accurately. In order to evaluate the effect of different seismic waves on the sloshing characteristics and free water surface shape of the fluid, FEM analysis was carried out by applying 5 artificial earthquakes covering the design response spectrum to the tank. Also, the effect of the ratio of the structure width to the fluid height on the slushing characteristics and the free water surface shape was analytically evaluated. Finally, structural analysis for water tank was carried out by applying Housner’s model, Westergaard’s model, and additional mass model using additional mass function obtained from this analytical study. The validity of the proposed additional mass model was verified by analyzing the analysis results.