Fatigue performance of root-to-throat cracks repaired by bonding steel: experimental and numerical investigations

Root-to-throat cracks are one of typical fatigue cracking modes in rib-to-deck welded joints of orthotropic steel bridge decks (OSDs). An efficient technique of non-destructive bonding steel plates (BSP) was proposed to address the cracking issue. A series of local full-scale test specimens with and without strengthening were per -formed under different loading cases. Meanwhile, the typical failure modes and fatigue performance of welded joints were evaluated. Subsequently, fracture mechanical models were developed to deepen the understanding on crack propagation behavior and strengthening effectiveness. Finally, a parametric study was carried out to explore the effects of various parameters on stress intensity factors (SIFs) at the crack tips. The results showed that fatigue cracks dominated the crack propagation of the welded throats in the case of rib bending. External BSP on rib-to-deck welded joints contributed greatly to the extended in-service life of existing cracked structures. To be more specific, the fatigue stress range response at the cracked region was reduced by an average of 90.6% by means of the BSP method. By comparing SIFs, it was found that the BSP retrofit method led to a reduction of at least 78%. The predicted directions of crack propagation agreed well with the observations from fatigue tests. Moreover, the thickness of bonded plates exerted more significant effects on fatigue improvement.