Finite element modelling and design of concrete wind turbine towers subjected to combined compression and bending

The combined compression and bending condition is primarily considered in the design of concrete wind turbine towers. However, the design methods specified in existing standards fail to accurately predict the compression-bending capacity of the concrete tower upon the occurrence of cracks at horizontal joints. Therefore, this study aims to develop a new method for calculating the compression-bending capacity of concrete wind turbine towers. A finite element (FE) model was firstly developed and validated against experimental results regarding to the load-displacement curves, compression-bending capacities and failure modes. Upon validation, a parametric study was conducted to generate 125 numerical results and investigate the effects of key parameters, including concrete strength, yielding strength of the steel reinforcement, precompression ratio, cross-sectional dimensions, and prestressing force. The results indicated that the compression-bending capacity of concrete wind turbine towers are significantly influenced by the concrete strength, cross-sectional dimensions, and precompression ratio. Based on the newly generated results, new design rules are proposed and compared against both experimental and numerical results. Subsequently, the applicability of the existing design methods of compression-bending capacity for concrete wind turbine towers was evaluated; unfortunately, they were found to be unsafe due to the neglection of the increment of prestressing force and the change of the cross-sectional second moment of inertia. Finally, the new design method yields a mean ratio of predicted to experimental (and simulated) compression-bending capacity of 1.01, with a coefficient of variation (CoV) of 0.0454, demonstrating enhanced accuracy and consistency.