Investigating Different Horizontal Bracing Schemes on the Deflection and Behavior of Latticed Steel Transmission Line Towers

In steel lattice transmission line towers, an internal horizontal bracing diaphragm is required to redistribute shear forces along the structure and to provide enough rigidity. Horizontal bracing is used in various configurations in a square layout to provide a stiffer system to assist in reducing distortion caused by nonsymmetric loads and oblique wind loads. The spacing of bracing diaphragm is assigned according to general stiffness requirements to maintain tower geometry, while the brace configuration could vary in complexity and adequacy. The main objective of this study is to examine the effect of various horizontal bracing schemes currently used in the industry. Six different bracing schemes are studied on three different tower types. The tower models were analyzed under several load cases including gravity and environmental loads, oblique wind load, cable loads, and maintenance and construction loads. The analysis of the schemes is carried with reference to both the tower lateral deflection and internal forces development in horizontal braces. The results of the analysis present recommendations on the most efficient diaphragm bracing scheme.