Hyperbolic Cooling Towers, Development and Practice

The development and practice of hyperbolic reinforced concrete cooling towers are described. The collapse of three large towers in England caused concern and it initiated research in this field in Belgium and England, both through analysis and with wind-tunnel models. Unlike ordinary structures for which projected wind forces are acceptable, hyperbolic towers have to be analyzed for the rapidly changing positive and negative wind pressures. The solution lies in the membrane theory preferably including the moments caused by deformations. To protect against ovalling, a strong top ring is recommended, while the transition between the thin shell and the diagonal columns has to be designed as a deep beam. Unyielding foundations are mandatory, otherwise prohibitive flexural moments effect the membrane forces. Continuous heavy ring footing are recommended either directly on soil or on pilings or caissons.