Optimisation of shear connector design and shear lag behaviour in composite continuous beam bridges using multi-scale finite element modelling

This study presents a multi-scale finite element modelling approach for full-scale continuous steel-concrete composite beam bridges, aimed at achieving a balance between computational efficiency and local accuracy. The method integrates detailed solid elements in critical regions, such as the negative moment zones and beam ends, with simplified beam elements elsewhere, using coupling constraints to ensure compatibility across scales. The approach is validated through static load testing of a two-span continuous beam, demonstrating strong agreement with experimental results and a significant reduction in computational time. Building on this framework, a full-scale three-span bridge model is developed to investigate the influence of shear connector parameters on structural performance in the negative moment region. The results show that reducing connector shear stiffness and increasing spacing can effectively release interface slip, reduce tensile stress concentrations in the concrete slab, and enhance crack resistance. Additionally, the model is used to analyse shear lag effects under realistic vehicle loading conditions. The findings reveal that eccentric loading markedly amplifies local tensile stresses, underscoring the importance of accounting for shear lag in serviceability and durability assessments. • Validated multi-scale FE model for composite continuous beam bridges cuts compute time 49.6% without compromising accuracy. • Reducing shear connector stiffness and increasing spacing significantly improves crack resistance. • Shear lag effects are shown to intensify under eccentric loading, with peak stress concentrations shifting across the slab width. • A performance-based connector design strategy is proposed, enabling targeted stiffness and spacing adjustments across moment regions.