As a tall structure supporting transmission lines, power towers must withstand various external forces (i.e., "loads"). The core of load calculation is to determine the magnitude, direction, point of application, and combination of various forces acting on the tower, providing fundamental data for calculating internal forces and deformations. Loads are categorized into permanent loads (gravity loads from conductors, ground wires, insulators and accessories, structural components, and various fixed equipment on the tower) and variable loads (wind and snow loads, conductor and ground wire tension, various additional loads from installation and maintenance, secondary loads caused by structural deformation, and various vibration loads). Loads acting on transmission towers can be classified according to their direction of action as lateral loads, longitudinal loads, and vertical loads.
Large-range loads: These are horizontal loads acting along the direction of the crossarm. Lateral loads include: wind loads on conductors and ground wires on the tower, the lateral distribution of conductor and ground wire tension on angle towers, the lateral wind load on the tower itself, and the lateral wind load on insulators.
Longitudinal loads: These are horizontal loads acting perpendicular to the direction of the crossarm. Longitudinal loads include: the component of conductor and ground wire tension in the direction perpendicular to the crossarm; the longitudinal component of wind load generated by oblique wind on the conductor and ground wire; the longitudinal wind load on the tower itself; the unbalanced tension of the ground wire; the breaking tension of the conductor and the supporting force of the ground wire during a break; and the traction load during installation and maintenance.
Envelope: the self-weight and ice weight of the conductor and ground wire; the self-weight and ice weight of the tower; the weight of insulators and hardware; the vertical component of the guy wire tension on guyed towers; and the weight of operators, tools, and accessories during installation and maintenance.
