Evaluation of the natural draught cooling tower shell using linearly and non-linearly numerical analysis

The shell shape of the natural cooling tower determines the sensitivity of the whole structure against wind excitation. This study analyses influence of the tower shell geometric parameters on the structural behavior, evaluated by linearly and nonlinearly numerical analyses. The goal of the study is to give an informative statement for the form-finding process of the cooling tower shell in the engineering practice. The generated 32 towers from an existing cooling tower are linearly analyzed base on the natural frequency. Further three representative models were selected, they were analyzed based on the buckling factor and the reinforced amount required according to a design guideline. The hyperbolic shell with overall radii as small as possible yielded not only a higher first natural frequency, thus less wind-insensitivity, but also a safer buckling behavior and a economical design due to less requirement of concrete and reinforcement. This advantageous structural behavior could be consistently verified in the nonlinear analysis, evaluated by load-deformation curves and damage indices based on the natural frequencies and modal contribution factors.