A steel tower typically consists of three sections: the tower head (including crossarms), the middle section, and the legs. Each section plays a different mechanical role.
The tower head directly bears the vertical load and horizontal tension of the conductors, converting these into pressure and bending moments on the tower body. The middle section acts like an elastic column, resisting the bending moments from the tower head and the wind loads it bears. The legs are responsible for distributing all the load to the foundation; therefore, their cross-sections are usually innovative, and their angle with the ground is rigorously calculated-too steep and stability is insufficient, too gentle and material is wasted.
The tower body's cross-section gradually narrows from bottom to top, forming a cone shape. This shape is not for aesthetic reasons, but based on the distribution of bending moments: the bending moment is greatest at the base and smallest at the top. The base requires a wider cross-section to resist the overturning moment.