Cold Reinforcement and Evaluation of Steel Bridges with Fatigue Cracks

Abstract

Cold reinforcement techniques refer to reinforcement methods that produce no or only low tensile residual stresses in structural details, avoiding new fatigue vulnerable details. To ensure the fatigue safety and extend the fatigue life of steel bridges, cold reinforcement techniques are proposed to stop the fatigue cracking of the critical details of orthotropic steel decks (OSDs) and web gap zones. Cold reinforcement techniques were evaluated by fatigue testing in the laboratory, in situ steel bridge case studies, and numerical fracture mechanics analysis using the extended FEM. Compared with drilling stop-holes, cold bonding of steel plates or bonding and bolting of steel angles have shown to effectively decrease local stresses, increase local rigidity, and extend fatigue lives. For in situ case studies on both a railway and a highway bridge, measured fatigue stress range spectra indicated that the bonding and bolting steel plate methods significantly enhance local rigidity and decrease local stresses. Numerical fracture mechanics results reveal fatigue stresses at the crack tip below the threshold of crack propagation.