Geometry and load eccentricity effects on the failure response of pultruded GFRP single-angle trusses

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Pultruded glass fibre-reinforced polymer (GFRP) trusses provide a lightweight and corrosion-resistant alternative for structural applications such as transmission towers, bridge components, and modular structural systems. However, planar trusses fabricated from open single-angle members remain susceptible to local instability and secondary effects induced by geometric asymmetry and load eccentricity, which may significantly influence their failure response. As such, this study presents an integrated experimental–numerical investigation of the failure behaviour of pultruded GFRP single-angle trusses subjected to concentric and eccentric nodal loading. Six specimens in rectangular, trapezoidal, and triangular configurations undergo load-controlled testing to examine the influence of truss geometry and load eccentricity on the structural response and failure behaviour of pultruded GFRP single-angle trusses. The results show that truss geometry governs the failure response, with the triangular trusses exhibiting the highest stiffness and load-carrying capacity together with the smallest mid-span deflection, and the rectangular trusses showing the lowest resistance accompanied by the largest deformation demand. Load eccentricity results in significant reductions in ultimate load and stiffness in all configurations, with the rectangular trusses showing a more pronounced loss of structural capacity, whereas the triangular trusses retain a larger portion of their initial resistance and stiffness. Furthermore, scanning electron microscopy (SEM) observations identify matrix cracking, matrix pulverisation, fibre–matrix debonding, fibre pullout, and fibre fracture as the governing micromechanical damage characteristics. In parallel, three-dimensional finite element models developed in ABAQUS predict the measured load–deflection response and governing failure patterns with reasonable agreement, with peak-load discrepancies ranging from 0.03% to 16.34%.