Simple Design Procedure for Liquid-Filled Steel Conical Tanks

Conical steel vessels, having an upper cylindrical section and supported by a reinforced concrete shaft, are becoming widely used for water containment in elevated tanks. However, the current codes of practice for water structures in North America do not include any rational method for designing such vessels. In this study, a simple and rational design procedure that considers instability, yielding, large deformations, geometric imperfections, and residual stresses is developed for these hydrostatically loaded steel vessels. The procedure is based on a verified finite-element model and employs a multiple-regression analysis to develop formulas that relate the maximum stresses resulting from the hydrostatic pressure to geometric and thickness parameters. The approach uses these formulas to permit the design of variable thickness liquid-filled conical tanks that are subjected to both hydrostatic and snow load. Verification of the design procedure is carried out to prove that the procedure is accurate, economical, and conservative.