Sixty-Degree Steel Angle Sections for Communication Towers with Triangular Bases

A triangular configuration is preferred over square configuration for communication towers due to significant weight reduction and less space for installation. Using 60° angles as leg members in triangular towers will facilitate the connection between the leg and bracing members, evading the use of bent-up gusset plates. The 60° angle sections are stronger in flexural buckling but weaker in torsional-flexural buckling. In this paper, experimental and numerical investigations are conducted at the component and structural levels to evaluate the torsional-flexural buckling behavior of 60° angle sections. Component-level experimental experiments, including material characterization and geometric imperfection studies, have been carried out on two types of typical 60° angle sections, such as v110×110×10 mm and v80×80×6 mm, with varying effective lengths, such that these sections fail in torsional-flexural buckling mode. Numerical investigations using nonlinear FEA software have been carried out for validation with experimental and ASCE/SEI 10-15 code buckling strength predictions. Full-scale prototype test conducted on a 5.5 m high roof-top triangular communication tower with antennae loads. The tower is fabricated using 60° angle leg members and conventional 90° angle sections for all other members. The leg member failed in torsional-flexural buckling mode, similar to component-level test results. Based on the numerical investigation, the structural performance in terms of deflection and self-weight is found to be 30% and 10% less when compared with similar triangular tower configuration subjected to same load using a 90° angle section as leg member with bent-up-gusset plates. Further, a comparative numerical investigation study carried out to examine the behavior of 60° angle sections at the structural level conducted on two numbers of a 24 m high triangular communication tower made of 60° and 90° angle sections, respectively, as leg members, designed for same wind speed and antennae loading. The deflection and self-weight of the 24 m high triangular tower made of 60° angle section as a leg member are 40% and 16% less compared with the triangular tower made of a 90° angle section as a leg member with bent-up gusset plates.