Fatigue process of rib-to-deck welded joints of orthotropic steel decks

Abstract

The numerous welded joints in orthotropic steel decks (OSDs) lead to a high probability of fatigue damage. One of the most detrimental problems is the severe reduction of the serviceability due to cracks in rib-to-deck welded joints, which require in-depth studies on the entire fatigue process. The linear elastic fracture mechanics has been proven to be effective in this aspect. When put into practice on actual projects, however, its accuracy and feasibility are largely dependent on features in various scales. This paper presents an investigation on the fatigue behavior of orthotropic steel decks with respect to multiscale concerns. By performing fatigue tests on OSD specimens welded by 15-mm-thick deck plates and 6-mm-thick stiffeners of S355 steel, the rib-to-deck weld toe crack that penetrates the deck plate is produced and the crack growth path is addressed using beach mark method. Afterwards, a two-dimensional local model of the rib-to-deck weld toe crack is built using the extended finite element method by which the stress intensity factors for early-stage cracks can be obtained. Based on the similar concept of nominal stresses, it can easily be linked to the macroscopic model and forms a non-concurrent method that enables to simulate the crack growth at rib-to-deck weld toe. As a result, a crack growth rate curve for the test specimen is given and different stages are analyzed with respect to the Paris law, indicating a clear influence of the early-stage fatigue cracks. The material constants of crack growth are obtained and validated, which may further be introduced to the fatigue assessment and life estimation for the maintenance work of OSDs.