Abstract
The cracks with different shape ratios propagating along the deck direction are extremely harmful for the deck-to-rib welded details in orthotropic steel decks (OSDs). To provide an effective and reliable fatigue life assessment method for OSDs, the 2D and 3D crack propagation simulations were carried out to solve the crack (including the penetrating crack) propagation problems based on linear elastic fracture mechanics (LEFM), respectively. Firstly, the fatigue experiment was carried out for the investigation of crack propagation characteristics and fatigue life evaluation of deck-to-rib weld details. Secondly, a solid finite element model (FEM) was established. The simulated hot spot stresses at the weld toe and the simulated nominal stresses at the weld root were compared with those of the experiment to verify the accuracy of the FEM. Thirdly, based on LEFM and the two-level method, the finite element method and the finite element/boundary element method were presented to analyze the penetrating crack with growth using the 2D stain model and 3D quarter-elliptical crack growth using 3D models with different initial shapes of the fatigue specimen respectively. Finally, the 2D and 3D numerical crack propagation morphologies, stress intensity factor ranges, fatigue life and crack growth rates were analyzed and discussed. The results indicate that the fatigue crack at the weld root of the specimen is an I-II-III mixed-type crack dominated by the I-type crack. The simulated fatigue life of 3D models is accurate with an error of about 10%. The fatigue life is mainly consumed in the initial stage of crack propagation. The fatigue life of the penetrating crack propagation simulated using the 2D stain model is only 60% of that of the 3D quarter-elliptical crack propagation. The initial shape of the crack is flatter, the fatigue life of the specimen is shorter, and the crack growth rate of it is faster. The penetrating cracks seriously affect the service life of the steel bridge decks. Therefore, it is necessary to detect the OSDs in time and take measures to prevent the further propagation of the crack.
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