Compressive Strength and Design Provisions for Continuous Steel Angle Braces in Telecommunication Towers: Stability-Based Approach

Abstract

Steel angle towers are commonly used in telecommunication infrastructure due to their structural efficiency and cost-effectiveness. Their performance under horizontal loading depends mainly on the behavior of their cross-bracing angles. When one brace goes into compression and the other into tension, the tensioned brace provides elastic restraint to the cross-bracing point through stress stiffening, which enhances the system’s buckling resistance. The magnitude of this interaction is governed by the tension-to-compression force ratio (T/C) which plays a critical role in defining the compressive strength of the bracing system. However, current design provisions for steel telecommunication towers offer inconsistent guidance for continuous cross bracing, especially under unsymmetrical loading that induces compression in both diagonals, leading to significant discrepancies in predicted strength. To address these inconsistencies, this study develops a detailed finite element (FE) model to study the compressive strength for continuous steel angle braces in telecommunication towers. The developed FE model is validated using full-scale experimental data and applied in an extensive parametric study of 220 bracing configurations covering a broad range of slenderness ratios, steel grades, and T/C force ratios. Results show that brace capacity is governed by global slenderness, force imbalance between diagonals, and the presence of redundant bracing. The FE analyses reveal a gradual reduction in compressive strength with increasing T/C, contrary to the abrupt strength drops assumed in current provisions. Although some provisions capture this trend more accurately, it remains sensitive to member slenderness. Based on these findings, a stability-based design approach is proposed to supplement current provisions, requiring both individual member and system-level buckling checks when multiple diagonals experience compression, offering improved accuracy while remaining compatible with existing design equations. The proposed design approach shows excellent agreement with the FE results, with a coefficient of determination approaching 1, confirming its accuracy and practical reliability.