A prediction method for the compression‐bending capacity of horizontal joints in externally prestressed wind turbine towers

Accurate evaluation of compression‐bending capacity is essential for the design of concrete wind turbine towers. After a horizontal joint opens, the unbonded external tendons do not follow the local concrete strain distribution, limiting the applicability of conventional annular‐section design methods. This study proposes a non‐iterative method that derives tendon strain increments from the global deformation of the tower using an equivalent plastic‐hinge model. The resulting expressions are combined with sectional force and moment equilibrium to predict ultimate bending capacity. Predictions are evaluated against 14 externally prestressed annular specimens reported in six studies and compared with two existing analytical models and three code‐based methods. The code‐based methods give mean predicted‐to‐measured moment ratios of 1.50, 1.53, and 1.79, corresponding to average overestimations of approximately 50%, 53%, and 79%. The proposed method gives a mean ratio of 0.95 and a coefficient of variation of 0.16. Its absolute mean bias is 5.4%, compared with 8.1% for the Tan JK model and 13.3% for the Ren W model—reductions of 33% and 59%, respectively. Parametric analysis indicates that capacity increases with concrete strength, varies non‐monotonically with precompression ratio, and decreases as the prestressing reinforcement ratio increases at a fixed precompression ratio. The method offers a direct calculation procedure for horizontal‐joint design, although validation at the larger diameter‐to‐thickness ratios typical of prototype towers is still needed.