Buckling of Stiffened Hyperboloidal Cooling Towers

With increasing dimensions of the cooling towers built of reinforced concrete, the buckling behavior becomes crucial in the proportioning of the shell. Ring stiffeners prove to be most effective in this respect with up to four stiffening rings the so called optimal position provides the highest efficiency. After five rings the equidistant positioning becomes effective as well. However, after a value of approx 6 this ratio doesn't influence the buckling load because the local buckling between the stiffening rings becomes decisive. The quality of the numerical analysis is checked by calculating the buckling loads obtained in tests on stiffened hyperboloidal models. The deviation between the theoretical results and experimental values is approximately the same and about 0.83 both for unstiffened models and stiffened models with five or nine rings. Also the high efficiency of the rings with ring depth to shell thickness ratio of about 6 could be verified.