A non-concurrent multiscale simulation of fatigue crack on orthotropic steel decks

The numerous welded joints on orthotropic steel deck lead to high probability to the emerge of fatigue cracks. Numerical simulation based on linear elastic fracture mechanics has been proven to be effective on reproducing the crack growth process. When put into practice on actual projects, however, its accuracy and feasibility are largely dependent on features in various scales. This paper presents a non-concurrent multiscale method on investigating the crack on orthotropic steel decks. According to the fatigue test, the rib-to-deck weld toe crack that penetrates the deck plate was addressed, and the key factors were the crack shape and size, especially for the shallow and long early-stage cracks. Therefore, a two-dimensional local model of rib-to-deck weld toe crack was built using extended finite element method, by which the stress intensity factors for early-stage cracks can be calculated. Based on the similar concept of nominal stress, it can be easily linked to the macroscopic model, and forms a non-concurrent multiscale method that enables to simulate the crack growth at rib-to-deck weld toe. As a result, a detailed analysis on different stages in crack growth rate curve were given with respect to Paris law, implying the influences from welding process on early-stage fatigue cracks. The results will benefit the fatigue assessment and life estimation of orthotropic steel decks, and may further be introduced to the maintenance work by combining with inspections