Numerical analysis of shear behavior and resistance of horizontally curved steel I-girders

Curved steel I-girders are widely used in modern bridge engineering, particularly in highway interchanges and urban viaducts, where horizontal alignment requires curvature. These elements are structurally efficient but present complex behavior, under shear, due to the combined effects of curvature, web slenderness, and bracing conditions. Existing design provisions, such as AASHTO and EN 1993–1–5, are primarily derived from the behavior of straight girders and may not fully capture the structural response of curved members in shear-critical regions. Although FprEN 1993–2 includes provisions for in-plan curved I-girders, these rules are applicable within specified ranges of slenderness and curvature, and their predictive performance for geometries outside such ranges has not yet been comprehensively assessed. This study presents a comprehensive numerical investigation into the shear behavior of curved I-girders using nonlinear finite element modeling. A wide parametric analysis is carried out, covering a range of web slenderness ratios, curvature levels, panel aspect ratios, and two distinct bracing effect configurations. The study evaluates both the elastic critical shear buckling force and the ultimate shear resistance, with particular attention to post-buckling behavior and the presence of reserve strength. The numerical results offer information about the influence of curvature on shear resistance and deformation patterns. It is shown that increased curvature reduces the ultimate shear strength, while higher web slenderness enhances post-buckling reserve strength. Comparisons with predictions from EN 1993–1–5 and FprEN 1993–2 reveal variations in accuracy, with both conservative and non-conservative estimates depending on the geometric and boundary conditions. These findings highlight the need to further investigate how curvature effects influence shear response, even at moderate levels.