Failure Analysis And Optimization Design Of Large-scale Natural Draft Cooling Tower

The natural draft cooling tower is widely used in the thermal power stations and other industrial departments, with the concrete thin-wall structure supported with columns at bottom. The safety of the large scale cooling tower under wind and earthquake is much important. This paper analyzes the failure modes of a large scale cooling tower according to working conditions in national code GB/T 50102-2003. Then the sequential quadratic programming method is applied to structural optimum design of the cooling tower. The main body of this paper includes two parts:Partâ… . The finite element model of the natural draft cooling tower is built with the commercial finite element analysis software ANSYS, while the strength failure mode and the buckling failure mode are analyzed, and the stresses of the cooling tower due to wind, gravity and temperature change are calculated. The results reveal that wind loading is the key factor to the design of the cooling tower. After that the critical wind velocities and buckling modes of the eigenvalue buckling and the geometrical nonlinear buckling are calculated in this paper, and the load-displacement curves of geometrical nonlinear buckling are plotted. The results indicate that the suction reduces the critical buckling wind velocity. The strength failure under earthquake is also studied, while the results demonstrate that the cooling tower can withstand both the minor earthquake of intensity 9 and the severe earthquake of intensity 7. The numerical results show that the dominant failure mode of cooling tower is the strength failure due to wind load rather than the buckling failure.Partâ…¡. Based on analysis results in partâ… , the sequential quadratic programming method is used for structural design to minimize the tower weight and to optimize other properties, using the commercial software Isight. Finally the obtained optimal solution indicates that the uniform thickness of the bottom half of tower shell should also be adopted to reduce the stress just like the upper half, which shows its great superiority compared with the original design of traditional variable thickness, and can simplify the construction process.