# Understanding the Seismic Resilience of Metallic Cylindrical Tanks Through Parametric Analysis
## 6 Conclusions
These analyses were performed using the LS-DYNA software, treating the FSI problem according to the ALE formulation. The modeling approach was verified by comparing the results from a shake table test performed by other researchers with the numerical results obtained from the model developed in this study. The comparison demonstrated that the chosen modeling approach provides a sufficiently accurate prediction of the tank's seismic response, making it a reliable reference for future research in this area. 7. Nonlinear transient analyses were performed to assess the seismic response of ten case study tanks, which were designed to represent both squat and slender configurations. Each tank was analyzed using the seismic excitation corresponding to the acceleration time history from the experimental test by [PERSON] and [PERSON] [42]. The pressure profiles obtained from these analyses exhibited similar trends across the five different \(R/t\) ratios investigated. A noticeable peak in pressures occurred at the top of the wall for both rigid and flexible wall tanks: around 0.9 normalized height (\(z/H\)). However, the \(H/R\) = 1.5 case study showed a smaller peak due to a significantly reduced convective contribution, which is attributed to the different slenderness of the containment structure. This peak has been shown to be related to the sloshing motion, specifically the impact of the convective wave on the tank wall, which generates the pressure peak. The \(H/R\) = 1.5 case represents the transition point between squat and slender tanks. Based on the analysis of all the cases studied, the following conclusions can be drawn: 1. For squat tanks (0.5 \(<H/R\) < 1.5), the largest pressure peak occurred in rigid tanks and decreased as the wall flexibility increased. 2. For slender tanks (1.5 \(<H/R\) < 6), the largest pressure peak occurred in flexible tanks and decreased as the rigidity of the wall increased. These findings highlight the significant influence of tank flexibility and slenderness ratio on the seismic pressure distribution, emphasizing the need for careful consideration of these factors in the design and analysis of cylindrical tanks subjected to seismic excitation. 8. The pressure profiles obtained from the FE analyses were compared with the predictions from the three standard approaches (EC8-4, NZSEE, and AWWA) using the input motion response spectrum and the combination rule for impulsive and convective pressure components specified in each corresponding code. Generally, a good agreement was observed in the lower part of the wall. However, the impact of the convective waves on the tank shell causes a peak in pressure at the top of the wall, which cannot be predicted by the design approaches proposed by the three regulations, except for the \(H/R\) = 1.5 case study. It is important to note that these peaks could lead to significant problems during seismic events and should be taken into account during the design of steel tanks. Although small discrepancies at the base can be easily accounted for in design, the considerable underestimation of pressures in the upper portion of the tank could lead to an unsafe and non-conservative design, particularly if there is a large reduction in thickness along the tank height. Comparing the pressure response values obtained from the FE simulations with those predicted by the standard codes, the following conclusions can be drawn:  
1. AWWA underestimated the FE results for all studied cases, including both squat and slender tanks. 2. EC8-4 for rigid tanks underestimated the FE results across all cases: both squat and slender tanks. EC8-4 for flexible tanks overestimated the FE results only for squat tanks (\(0.5<H/R<1.5\)) but underestimated the results for slender tanks (\(1.5<H/R<6\)). 3. NZSEE recommendations, both for rigid and flexible tanks, led to similar pressure values for squat tanks (\(0.5<H/R<1.5\)) but underestimated the FE results for slender tanks (\(1.5<H/R<6\)).