Stress intensity factor of double fatigue cracks at the rib-to-diaphragm connection in orthotropic steel decks

Abstract

This study investigates the interaction behavior of double fatigue cracks in rib-to-diaphragm connections of orthotropic steel decks (OSDs) through numerical simulations. Finite element models were developed using ABAQUS and FRANC3D software to analyze Mode I stress intensity factors (SIFs) under vehicle loading conditions. The numerical findings demonstrate that when vehicle loads approach both mid-diaphragm sides, the SIF of initial cracks increases due to interaction with artificial penetrating cracks. The study introduces an interaction factor (λ) to quantify this crack interference (amplification or reduction) effect. Parametric analyses reveal that interaction effects intensify with decreasing diaphragm thickness and increasing crack length. At diaphragm cutouts, crack interaction becomes more significant as initial crack shape ratios approach unity, while at weld locations, this effect diminishes with similar shape ratios. The research further develops a hybrid computational approach combining backpropagation neural networks with particle swarm optimization (BP-PSO) to predict multi-crack SIF interaction factors. Validation shows the model achieves satisfactory prediction accuracy, offering practical value for fatigue crack assessment and repair strategies in OSD bridge connections. The proposed methodology and findings provide engineers with quantitative tools for evaluating crack interaction effects in actual orthotropic deck applications.