Axial compression behavior of angle steel members reinforced non-destructively with double-sided GFRP

As the service life of transmission towers increases, there is a significant demand for upgrading existing structures. This study investigates angle steel, a primary structural component in lattice steel transmission towers, and proposes a non-destructive double-sided reinforcement scheme using GFRP material. This scheme is designed for convenient installation on existing transmission towers. The strengthened members were subjected to axial compression tests, which revealed that the non-destructive reinforcement significantly improves the bearing capacity by 22.32% compared to unreinforced members. A refined finite element model (FEM) of the strengthened member was developed, and the axial compression tests confirmed the reliability of the simulation, demonstrating the viability of using composite materials for angle steel reinforcement. The study explores how the double-sided reinforcement system enhances bearing capacity by examining the impact of four parameters: slenderness ratio, reinforcement ratio, bolt spacing, and the thickness ratio of the strengthening component on failure mechanisms and bearing performance. The results indicate that the improvement in bearing capacity is primarily due to the lateral elastic constraint provided by the strengthening component, which enhances the flexural stiffness of the member. Additionally, as the slenderness ratio of the substrate member increases, the improvement rate of the bearing capacity also increases. Based on the parametric analysis, a modified design approach incorporating the specific constraints of the non-destructive scheme is proposed and validated. The results of this study can serve as a reference for the reinforcement and upgrading of in-service transmission towers.