Study on thin-walled Circular Hollow Section with and without stiffeners subjected to bending

The wind industry continues to grow rapidly throughout the world. The turbine tower, which plays an important role in supporting the equipment, is mainly subjected to bending moment caused by lateral wind load or earthquake load. Commonly, thin-walled Circular Hollow Section (CHS) is widely used in wind turbine towers. However, there is little research on this part. This paper presents an experimental study by using 6 thin-walled steel tubes and 4 thin-walled steel tubes with stiffeners. The diameter-to-thickness ratio and those for stiffener are main parameters, and in design the diameter-to-thickness ratio varies from 100 to 300. Based on the finite element model, the influence of initial geometric imperfection in steel tube is analyzed. The experimental results show that local buckling appeared at the top of compression part could result in the significant decrease of ductility and load-carrying capacity. The stiffeners, however, could effectively delay the appearance of local buckling and change the failure modes of steel tube. Compared with the specimen without stiffeners, the load-carrying capacity and ductility of specimens with stiffeners can be improved. The bending capacity could decrease due to the appearance of geometric imperfection, and the influence will become more evident for CHS with the diameter-to-thickness ratio increasing. Hence, during fabrication the initial geometric imperfections and their amplitudes in CHS tubes should be strictly controlled.