Analysis and design of elevated liquid-filled reinforced concrete conical tanks

Reinforced concrete conical tanks are used in municipalities and industrial applications as liquid containing vessels. These tanks can be ground supported tanks or elevated on a supporting shaft. Although most design codes provide guidelines for rectangular and cylindrical tanks, no guidance is provided in these codes for conical tanks. This study focuses on assessing the accuracy of a design approach based on the provisions of Portland Cement Association Circular Concrete Tanks without Pre-stressing code for cylindrical tanks combined with an equivalent cylinder approach provided by the American Water Works Association-D100. Several reinforced concrete conical tanks with different geometric configurations are analyzed under the effect of hydrostatic loading using this approach. The internal forces obtained according to code provisions are compared with those predicted by a linear finite element analysis model developed for all studied tanks. The finite element analysis model is based on a degenerated consistent sub-parametric triangular shell element developed in-house. The results of this comparison show that Portland Cement Association Circular Concrete Tanks without Pre-stressing approach leads to larger hoop tension and smaller meridional moment compared to those obtained from the finite element analysis. Therefore, the Portland Cement Association Circular Concrete Tanks without Pre-stressing provisions combined with the equivalent cylinder approach lead to an inadequate design if applied to conical-shaped tanks.