Shear resistance of bridge I-girders with diagonal stiffener: Design proposal

Steel I-girders with diagonal stiffeners offer an effective means of increasing shear resistance in bridge applications by enhancing both elastic buckling and post-buckling resistance. However, no dedicated design rules exist for such configurations in current structural design standards, particularly for carbon steel girders. This study addresses this gap through an extensive numerical investigation of the shear buckling behaviour and ultimate resistance of web panels stiffened along the compression diagonal. A finite element model (FEM), validated against full-scale experiments, supports a broad parametric study covering aspect ratio, web slenderness, stiffener rigidity and geometric imperfections. The numerical results are used to assess existing resistance models, to develop a new expression for the shear buckling coefficient, and to propose several design models for ultimate shear resistance. A reliability assessment confirms compliance with Eurocode target safety levels. The study provides the first validated and comprehensive design framework for carbon-steel I-girders with diagonal stiffeners placed along the compression diagonal, bridging a key gap in current design standards and enabling more efficient and reliable shear design of steel bridge girders. • Extensive FEM study on I-girders stiffened with a single-sided flat diagonal stiffener along the compression diagonal. • New shear buckling coefficient expression calibrated against 4900 LBA simulations. • Five ultimate shear resistance models benchmarked against 441 GMNIA analyses. • Proposed design models provide accurate, safe-side predictions and meet Eurocode reliability targets.