Rib loading effects on weld root fatigue failure modes at rib‐to‐deck welded joint

Abstract

The service life of orthotropic steel decks is dependent on the fatigue resistance of rib-to-deck welded joints, which is often tested using two kinds of experimental models in terms of the rib loading condition. Different weld root fatigue failure modes have been observed in the different models, but the role of rib loading remains unclear. This paper aims to clarify the effect of rib loadings on the weld root fatigue failure modes at rib-to-deck welded joints. The loadings are decomposed into the deck loadings and rib loadings according to the principle of superposition. Formulae of the weld root notch stress intensity factors and T-stress under rib loadings are developed by multiparameter regression analysis and subsequently used for the local stress analysis. The fatigue failure modes determined from the local stress field agree well with the experimental results. The results reveal that the weld root failure modes depend on the rib loadings but are independent of the weld geometries. The averaged strain energy density (SED) that can capture both weld geometry and loading condition effects is used to correlate the fatigue test data of different weld root failure modes. The SED is capable of evaluating the fatigue strength of the rib-to-deck welded joint failed by different weld root failure modes with a narrow scatter band. K E Y W O R D Sfatigue failure mode, fatigue test model, local stress field, notch stress intensity factor, weld geometry

Fatigue failure modes of rib‐to‐deck joints under the multiaxial stress states caused by various wheel loading characteristics

“…Considering the diversity of fatigue failure modes, it is crucial to determine the dominant failure mode for fatigue life prediction. 8 Owing to the complexity of the bridge deck structure, it is difficult to accurately calculate the nominal stress at the fatigue failure location based on classical mechanics methods 9 ; similarly, owing to the characteristic of the evaluation method, the hot spot stress method can only be applied to the issues that fatigue cracks originate from the weld toe 10 ; comparatively, the structural stress method, which is based on the mechanic's principle of the free body cut, could evaluate the fatigue performance of complex structures in the case of both toe failure and root failure. 11 Yang et al 12 analyzed the fatigue behavior of welded joints in OSBD through the above-mentioned evaluation methods; the traction structural stress with 95% confidence intervals is more accurate than those calculated by the other S-N curves based on nominal, hotspot, and effective notch stresses.…”

“…By comparison, the fatigue failure mode of U‐rib toe has been reported 7 ; however, it was less focused and researched. Considering the diversity of fatigue failure modes, it is crucial to determine the dominant failure mode for fatigue life prediction 8 …”