FSI effects and seismic performance evaluation of water storage tank of AP1000 subjected to earthquake loading

• Water sloshing and oscillation of water tank under earthquake are simulated by FEM.
• The influences of various water levels on seismic response are investigated.
• ALE algorithm is applied to study the fluid–structure interaction effects.
• The effects of different water levels in reducing seismic response are compared.
• The optimal water level of water tank under seismic loading is obtained.

The gravity water storage tank of AP1000 is designed to cool down the temperature of containment vessel by spray water when accident releases mass energy. However, the influence of fluid–structure interaction between water and water tank of AP1000 on dynamic behavior of shield building is still a hot research question. The main objective of the current study is to investigate how the fluid–structure interaction affects the dynamic behavior of water tank and whether the water sloshing and oscillation can reduce the seismic response of the shield building subjected to earthquake. For this purpose, a fluid–structure interaction algorithm of finite element technique is employed for the seismic analysis of water storage tank of AP1000. In the finite element model, 8 cases height of water, such as 10.8, 9.8, 8.8, 7.8, 6.8, 5.8, 4.8, and 3.8 m, are established and compared with the empty water tank in order to demonstrate the positive effect in mitigating the seismic response. An Arbitrary Lagrangian Eulerian (ALE) algorithm is used to simulate the fluid–structure interaction, fluid sloshing and oscillation of water tank under the El-Centro earthquake. The correlation between seismic response and parameters of water tank in terms of height of air (h1), height of water (h2), height ratio of water to tank (h2/Hw) and mass ratio of water to total structure (mw/mt) is also analyzed. The numerical results clearly show that the optimal h2, h2/Hw and mw/mt to structure are 8.8 m, 0.7458 and 5.7235%, which can reduce the seismic response under earthquake loading most effectively. In addition, the maximum pressure distribution, maximum principle stress distribution, oscillation frequency and overturning moment of water tank and shield building are also obtained and analyzed.

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