Constrained Floatation to Prevent Above-Ground Storage Tank Failures during Flood Events

Document Type

Article

Publication Date

10-1-2025

Abstract

This research aimed to study the feasibility of constrained flotation of above-ground storage tanks (ASTs) as a structural mitigation measure during flood and storm surge events. Conventional structural mitigation measures, such as anchor chairs and straps, have proven inadequate in preventing dislocation, buckling, and bottom plate failures during storm surge and flood events. Therefore, a novel approach of constrained flotation for ASTs was proposed, allowing tanks to rise with flood waters to a height where these failures, mainly bottom plate failure, do not occur. First, analysis was performed to assess the stability of ASTs during flotation and to calculate the critical surge height required for flotation. Feasibility analysis was performed for 5-m-diameter and a 70-m-diameter tanks using finite-element analysis (FEA). The behavior of tethered tanks during flotation with various anchor chair configurations and placement of anchor chairs were assessed, and stresses were recorded in the tank bottom plates and shells. The findings revealed that the bottom plate can fail before flotation for a 5-m-diameter tank, which suggests that the conventional anchor chair design recommended by the American Petroleum Institute (API) 650 is ineffective for constrained flotation. To address this issue, the number of anchor chairs were increased, delaying yielding of the bottom plates; however, this could be cost-prohibitive. Two other anchor chair configurations were also analyzed, and they were ineffective for constrained floatation. Finally, shifting anchor chairs upward by 0.3 m allowed tanks of both diameters to achieve floatation before bottom plate failure or shell failure, thereby demonstrating the proof of concept for cost-effective constrained flotation of tanks.

Publication Source (Journal or Book title)

Journal of Structural Engineering

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