Dynamic Study Of Hyperbolic Cooling Towers

The cooling tower is the device used to complete hot commutation between water and air, and it is in common use in the industry .Therefore, the cooling tower occupies an importance position in industry construction .Hyperbolic cooling tower is a kind of typical axisymmetric revolve thin shell. The current typical large cooling tower is about 150m high with the bottom diameter about 100 m. Once the cooling tower falls in, the result will be very seriously. The most cooling towers were built successfully, and are running in good condition. But there are also some cooling towers broken down under the strong wind or strong earthquake in the world. For example, three cooling towers, which are the part of England Ferrybrighe power plant, collapsed under strong wind at November 1,1965. Thereby, engineers gradually know that it is important to take vibration computing when design the large cooling towers.The free vibration characteristic of cooling tower is the base to compute the wind and earthquake response of cooling tower. This paper has done some research on free vibration of cooling tower, which is based on the varying section pole free vibration theories.Firstly, the author looked back the development process of research method for pole free vibration, and analyzed the merit and weakness of the main method; Secondly, the author theoretically deduce out the free vibration differential eguation of revolving shell, which is based on some basic presume. At the course of deducing , both consider the bend moment and shearing force, and it makes more near to the actual problem. Then this paper simplified the differential eguation contraposing the cooling tower which is a special structure, and adopted the power series method to solve the differential eguation. Among the engineering literatures worldwide, there are no similar method to calculate free vibration of revolving shell, so this method has certain of unique. Finally the author analyzed variety factors which may influence the vibration frequency and mode of cooling tower.In order to make clear accuracy of the result, this paper made dynamical analysis to hyperbolic cooling tower by the large finite element software ANSYS. And consequently made the contrast of calculation result that ANSYS computed and this paper brought up.