Static behavior of the prestressed concrete wind tower section under combined compression-bending-shear-torsion loading

The prestressed concrete wind towers have applications potential in lower wind velocity region. The calculation of the ultimate limit states of thin-walled concrete structures under combined loads has attracted widespread attention. In this paper, a series of works have been conducted on its combined compressive-flexural-shear-torsional behaviour. A test system was designed using a combined loading method and considering various types of damage. The results show that the composite failure modes can involve multiple failure phenomena occurring simultaneously. Increasing the reinforcement ratio can enhance the post-yield bearing capacity of the specimens but has little effect on their stiffness. Finally, based on the unified formula for the ultimate bearing capacity of reinforced concrete, two assumptions of the eccentric compression formula for circular ring sections were derived using the strut-and-tie model and compared with the test results. The results indicate that the method recommended by the code is generally conservative for many conditions but has higher coefficient of variability. In contrast, the improved method reduces computational variability by 28.8 % while maintaining safety, providing more consistent and reliable predictions. This indicates that the improved method exhibits higher applicability across various loading conditions. The improved method addresses the gaps in current codes for design under combined loading conditions, integrating the verification of individual loading states into a more effective verification approach.