Distortion of Steel Tanks Due to Settlement of Their Walls

Abstract

The relationship between settlements and lateral deflections of the walls of floating‐roof steel tanks, and methods that can be used to estimate lateral wall deflections, are the main focus of this paper. As the walls of floating‐roof steel tanks settle unevenly, the upper parts of the walls deflect inward or outward, producing what has been termed “ovalization” of the tank. Ovalization leads to problems with floating roofs. Inward deflections may cause the roof to bind. Outward deflections may cause loss of seal and resulting emission problems. The amount of inward or outward deflection of the walls of floating‐roof tanks can be estimated readily once the basic shape has been recognized and the deformation axes, called fold lines, have been located. A simple procedure for recognizing fold lines and for calculating lateral deflections of walls is explained. Comparisons with other methods of analysis and with field measurements show that the fold‐line method is accurate enough for practical purposes, and that it provides a clear understanding of tank deformations.