Effects of imperfections on joint bearing capacity of segmented tower structures. Hybrid tower structures for wind turbines have become established in recent years, especially for turbines with large hub heights. The upper part of these towers consists of steel sections, whereas the lower part is made up of prestressed precast concrete rings. The horizontal joints between the precast concrete elements are usually designed as dry joints. Due to the lack of a compensation layer in the joint, increased demands are made on the accuracy of the joint surfaces. From measurement data of real segments of wind turbines, it could be deduced that the joint surfaces show imperfections with respect to the cross-sectional shape and flatness. Numerical simulations were used to investigate the influence of these imperfections on the joint support behaviour under combined loading of prestressing, bending and torsion. It is shown that, depending on the type of imperfection and the degree of prestressing, imperfections can have a considerable influence on the joint load-bearing behaviour.