Nonlinear stability analysis of steel cooling towers considering imperfection sensitivity

There is a lack of investigation on the nonlinear stability analysis of large steel hyperbolic cooling towers considering imperfection sensitivity. In this paper, nonlinear stability analysis of 150m-height steel hyperbolic cooling towers was assessed. Models with five structural systems were established, including two types of reticulated shells (i.e., single-layer and double-layer shells) and three forms of girds (i.e., triangular grid, rectangular grid and square pyramid grid). Additionally, geometrically and material nonlinear stability analyses for more than 220 cases were conducted considering various distributions and amplitudes of imperfections. The results showed that the five hyperbolic steel cooling towers are of relatively low imperfection sensitivity, which is different from most other thin-walled shells, and the imperfection sensitivity of rectangular grid is high, while triangle grid and square pyramid grid are of low imperfection sensitivity. In addition, structures with double-layer reticulated shells are more sensitive to imperfection than those with single-layer ones. It is recommended that the design of steel cooling towers can give priority to the scheme of single-layer reticulated shell with triangular grid. Furthermore, the imperfection amplitude of H/300 could reasonably represents the most unfavorable instability state for this type of structures.