Evaluating Large Aboveground Storage Tanks Subject to Seismic Loading: Part II — Explicit Dynamic Analysis With Liquid Sloshing Effects

Abstract

The dynamic response of storage tanks subjected to seismic loading is complex. Analyzing the structural response of a tank is not only dependent on accurately modeling the major design features and simulating the seismic loading, but also the sloshing of the fluid contained within the tank can affect the overall behavior and likely failure modes. Advanced dynamic simulation techniques, such as the ones discussed herein, permit comparison between these closed-form methods and computational predictions; that is, any potential conservatism or lack thereof associated with traditional design by rule methodologies can be identified using computational analysis. Additionally, for tanks that were not originally designed to a modern Code or recommended practice that includes consideration for seismic loading, the computational analysis methods discussed in this study offer a means to evaluate the structural integrity of vintage tanks under seismic loading conditions that are still in service today. This paper discusses explicit dynamic finite element analysis (FEA) techniques to simulate seismic loading on a large, aboveground, in-service Ammonia storage tank that carries a high consequence of failure. The fluid-structure interaction and sloshing behavior of the contained fluid are directly accounted for. Commentary on using smooth particle hydrodynamics (SPH), coupled Eulerian-Lagrangian (CEL), and computational fluid dynamics (CFD) analysis techniques is provided. The underlying methodology behind these simulation techniques is discussed, and the overall dynamic response of the tank is investigated. The results from the explicit dynamic seismic simulations are compared with the current seismic design guidance provided in API 650 [1] and equivalent static simulation techniques (documented in Part I of this study [2]). Furthermore, this case study highlights a practical application where advanced analysis is employed to investigate a real-life fluid-structure interaction problem.