Wind Effects on Water Towers-influence of Various Dynamic Parameters

Wind flows relative to the surface of ground and produces loads on the structures standing on the ground. The effect of the wind on the structures is of prime importance. Most of the designers consider the static effect of wind on the structure. But for tall structures the wind interacts with the structure dynamically. The Indian standard code IS 875 (Part-3) 1987 deals with the wind effects on the structures. Water towers are critical structures from the point of the wind effect. Towers of height 16 m, 20 m, 24 m and 28 m are considered in the present analysis. Fundamental frequency is computed by the method given in Indian standard IS 1893-1984. In the computation of fundamental frequency two conditions a) Tank empty and b) Tank full with water are considered. It is found from the study that static pressures are less compared to those given by the gust effectiveness factor method (GEFM). Dynamic interaction between the fluctuating wind component and the structure are considered in GEFM and equivalent static wind pressures are evolved. GEFM is more rational and realistic and recommended for wind load design of water towers.