Evaluation of load-carrying capacity of horizontal joints in concrete wind turbine towers

Concrete wind turbine towers are typically subjected to complex combined loading, including compression, bending, shear, and torsion, due to wind actions and prestressing forces. However, current design methodologies are inadequate for accurately assessing the load-carrying capacity of horizontal joints under such multi-axial stress conditions. To accurately evaluate the load-carrying capacity of horizontal joints in concrete wind turbine towers subjected to combined compression, bending, shear, and torsion, three scaled-down concrete tower specimens were tested under representative multi-axial loading conditions. The failure modes, load-displacement responses, and other key parameters were measured and analysed. The results demonstrated that the torsional and shear resistance of the horizontal joint regions was primarily governed by the frictional force developed at the joint interface as a result of prestressing. While higher prestress level enhanced the ultimate load-carrying capacity, they also led to a reduction in the ductility of the specimens. A refined finite element (FE) model was subsequently developed in ABAQUS and calibrated against the experimental results. Building upon established calculation methods for evaluating the torsional and flexural capacities of horizontal joints in concrete towers, and based on the fundamental form of the interaction equation for structural load-carrying capacity under combined loads, a new analytical framework was established to evaluate the load-carrying capacity of horizontal joints under combined loading conditions. Based on the refined FE model, a series of parametric numerical analyses were performed. Subsequently, the coefficients in the proposed evaluation equations were calibrated using the numerical simulation results, leading to the development of a comprehensive method for evaluating the load-carrying capacity of horizontal joints.