Major earthquakes have demonstrated that Natech events can be triggered by liquid overtopping in liquid storage tanks equipped with floating roofs. Thus, research on the dynamic behaviour of steel storage tanks with floating roofs is still required. In this paper, the seismic risk against liquid overtopping in a real steel storage tank with a floating roof was analysed using a simplified model that was validated by a refined finite element model based on the arbitrary Lagrangian-Eulerian approach. The simplified model utilizes the Lagrangian of a floating roof-fluid system and is capable of providing a response history of the floating roof. It was demonstrated that it could predict the maximum vertical displacement very accurately, while some differences were observed in the response history of vertical displacement. The computational time for a single response history analysis based on the simplified model amounted to a few minutes, which is significantly less demanding compared to hours required for response history analysis in the case of the refined FE model. The simplified model is thus appropriate for the seismic fragility analysis considering the overtopping limit state. It is shown that the fragility curves are significantly affected by the liquid filling level. The risk for liquid overtopping is quite high in the case of a full tank. However, by considering the variation of filling level during the year, the overtopping risk was observed reduced by approximately 30%. Alternatively, the approximate fragility analysis for the liquid overtopping can be performed by utilizing the Eurocode formula for the vertical displacement of liquid. This approach is straightforward, but the formula does not account for the higher mode effects, which may result in overestimated seismic intensity causing overtopping, as discussed in the paper.

重大地震表明，Natech事件可以由配备浮顶的储液罐中的液体超载引发。因此，仍然需要研究具有浮顶的钢制储罐的动力特性。在本文中，使用简化模型分析了在具有浮动顶板的真实钢制储罐中液体翻倒的地震风险，该简化模型已通过基于任意拉格朗日-欧拉方法的改进有限元模型进行了验证。简化模型利用了浮动屋顶流体系统的拉格朗日模型，并且能够提供浮动屋顶的响应历史。结果表明，它可以非常准确地预测最大垂直位移，而在垂直位移的响应历史中观察到一些差异。基于简化模型的单个响应历史记录分析的计算时间为几分钟，与精简的FE模型情况下响应历史记录分析所需的时间相比，所需时间明显更少。因此，考虑到超越极限状态，简化模型适用于地震脆性分析。结果表明，脆性曲线受液位的影响很大。在满罐的情况下，液体翻倒的风险非常高。但是，通过考虑一年中的填充水平变化，可以发现超车风险降低了约30％。可替代地，可以通过利用用于液体的垂直位移的Eurocode公式来执行用于液体溢出的近似脆性分析。