On the imperfection sensitivity and design of buckling critical wind turbine towers

• Analysis of wind turbine tower shell with state-of-the-art imperfection concepts. • Summary of the results of the international shell buckling exercise. • Improved version of the popular single-perturbation load approach (SPLA) presented. • Potential for significantly increased design factors for plastic buckling is shown by means of finite element analyzes. Wind turbine towers pose major challenges for design engineers due to their complex geometry, nonlinear material behavior and imperfection sensitivity. In service, these thin-walled shells are burdened by a combination of complex load cases and prone to buckling. In fact, one of the main design drivers of wind turbine towers is stability failure for which often the design recommendation of the EN-1993–1–6 are used. Recently an international shell buckling exercise was caried out by the team behind the EN-1993–1–6 design standard. Within this exercise 29 teams from academia and industry were asked to perform a series of linear and non-linear finite element simulations of an 8-MW multi-strake steel wind turbine support tower segment. In general, the linear and nonlinear analyzes posed no challenge for the shell buckling experts from around the world. However, the imperfection sensitivity analysis results scattered significantly among the participants. In addition, there was little consensus as to whether the given tower design is actually safe. The authors, whose background is aerospace engineering, participated in this exercise and show in this article how they overcome the challenges of this typical civil engineering problem. Among linear and non-linear analyzes the authors show the results of state-of-the-art shell buckling concepts which were developed for aerospace shells like interstage tanks and adapters but are also applicable to wind turbine towers.