The critical buckling load factor λcr is routinely used as predesign indicator for natural-draft cooling towers, yet its safety meaning is often opaque because imperfection sensitivity and modelling options are embedded implicitly. In this study, λcr is formalised as a product of partial contributions within a screening-level predesign framework—?not a normative limit-state format—and the contributions associated with geometric imperfections and FE discretization are calibrated explicitly. Eigenvalue analyses on representative tower geometries under combined self-weight and wind actions are complemented by imperfection-sensitivity curves and a systematic mesh/element-type study. The numerical implementation is additionally verified against published benchmark towers to provide a traceable reference before the parametric analyses. The results show that admissible modelling options can produce non-negligible scatter in λcr, while realistic geometric imperfections lead to a comparatively stable range. By separating actions, material, brittle failure, imperfection and discretization contributions, λcr can be interpreted consistently as a predesign global stability factor of the order of four for typical cooling-tower configurations, with the discretization-related term interpreted as a framework-dependent epistemic contribution, providing a transparent bridge between linear indicators and nonlinear verification.
Tomás et al. (Sat,) studied this question.