Study on ultimate bearing capacity of main member in transmission tubular tower leg

Transmission tubular towers are widely used as voltage increasing. One assumption usually made in transmission-tower analysis is that the joints are pinned. However, due to the fabrication difficulties, this assumption is rarely realized. Thus in practice, the tower members may produce secondary stresses not included in the analysis. Space tower leg structure model test and multi-scale FEM calculation were performed to investigate the magnitude of the secondary stresses and the effect on the ultimate bearing capacity of the main member in the tower leg according to the Chinese Standard Code of Practice. The result indicates that the secondary stresses of the main member in the tower leg could be up to 58% of the axial stress significant enough to cause failure of the main member even under normal working-load conditions. Meanwhile, it has been conclusively shown that the influence of the secondary stresses less than 30% of axial stress of main members is negligible, and the failure mode of the main member for the structure design is the plastic zone near the tower foot extends beyond the specifications' limit.