Optimum position and minimum flexural rigidity of longitudinal stiffeners in steel web plates subjected to bending-shear interaction

This study investigates the optimum position and minimum flexural rigidity of longitudinal stiffeners for steel web plates under coupled bending and shear stresses. Given that existing codes and literature mostly focus on pure bending or shear, a systematic stiffening design framework for bending-shear interaction is established by integrating finite element eigenvalue buckling analysis with mathematical optimisation algorithms. Parametric analyses are carried out on steel web plates with 1–3 longitudinal stiffeners, covering a wide range of geometric and stress parameters. The optimum stiffener position is determined by maximising the buckling coefficient, and the minimum flexural rigidity is defined to ensure effective restraint of web subpanels. Comparisons with existing codes show that current stiffness provisions may be unconservative under bending-shear interaction, indicating the need for refined design methods. The optimisation results are used to train artificial neural networks, which accurately capture the nonlinear mapping between input parameters and optimum stiffener designs. A graphical user interface tool is further developed based on the trained models for practical engineering application. The proposed framework and tool provide valuable guidance for the design of stiffened steel web plates under complex stress states.