Buckling Behavior of Schifflerized Angle Sections

Abstract

Triangular-based communication towers result in significant weight reduction compared to conventional square-based towers. Hot-rolled 90° steel equal angle sections with bent-up gusset plates are used for triangular towers, since 60° angles are not readily available in India. In triangular towers, the included angle between two flanges of the main leg member shall be 60° for smooth connection between leg and bracing members. The required included angle of 60° between the two flanges of a leg member can be achieved by “schifflerizing” the hot-rolled 90° angles. Numerical models were developed for the three different schifflerized angle sections 90 × 90 × 6 mm, 100 × 100 × 8 mm and 130 × 130 × 10 mm using general purpose finite element software NE-Nastran and calibrated with the test failure modes. Using this as base model, parametric studies are conducted on the same three angle sections by varying the lengths from 500 to 2500 mm. The compression capacities of these angles are predicted using the analytical methods given in the literature and compared with the parametric study and the available test results. For schifflerized angle sections, the warping constant is maximum when 90° and 60° flange portions are equal. The study result shows that schifflerized angle sections with width-to-thickness ratio ‘w/t’ below 13 are governed by torsional–flexural buckling up to slenderness ratio 70 and the sections with ‘w/t’ ratio above 15 are governed by flexural buckling.