Abstract
An orthotropic steel deck (OSD) has a complicated structure, and its fatigue life is mainly determined by various welding details. Fatigue assessment of deck-to-rib welding details (DRWDs) under long-term train loads is an important concern for engineers. Properly assessing the initial residual stress and the mechanism of stress relaxation in DRWDs under long-term external loading is a prerequisite for predicting the fatigue damage and service life of OSDs. In this paper, a finite element analysis method is proposed to calculate the residual stress relaxation in DRWDs of OSDs under constant/variable amplitude cyclic loading. First, experiments on full-size OSD specimens were carried out using the hole drilling strain-gauge method, and the multi-axial distribution characteristics of residual stress on the sub-surface of the deck were obtained. On this basis, a refined residual stress analysis model of DRWDs using thermal-structural sequence coupling analysis and life and death unit technology is established, and the accuracy of the model is verified by the test data. Second, a coupling stress analysis model that considers the welding residual stress and mechanical stress using cyclic plastic constitutive model is established. The combined influence of number of cycles, stress amplitude, and stress ratio on multi-axial residual stress relaxation effect under constant/variable amplitude cyclic loading is investigated. Finally, a release formula of welding residual stress relaxation coefficient is proposed based on the external loading stress amplitude, stress ratio, and material yield stress. The results show that (1) with the increase in the number of loading cycles, the stress decreases until it is stabilized, while the global distribution of welding residual stress remains unchanged. Most of the welding residual stress release (about 95%) occurs in the first cycle; (2) the residual stress relaxation decreases with the increase in stress amplitude and increases linearly with the stress ratio; (3) the residual stress release is controlled by the maximum amplitude stress in the variable amplitude cyclic loading. After the residual stress is released, the stress will not continue to be released if the DRWDs have the same or smaller amplitude loading.
Highlights
Orthotropic steel decks (OSDs) have been widely used as main girders in long-span bridges as a result of their high load-loading capacity, light weight, excellent aerodynamic, and speedy construction [1,2]
Fifteen years after the Rio-Niterói Bridge was built in Brazil and opened to traffic, it was found that serious cracks of OSDs had developed, mainly distributed in deck-to-rib welding details (DRWDs)
The influence of cyclic reinforcement on the ratchet effect and the stress relaxation effect was considered by using a Chaboche combined hardening model (CCHM), which includes the characteristics of the kinematic hardening model and the nonlinear isotropic hardening model based on the Von Mises flow rule [27]
Summary
Orthotropic steel decks (OSDs) have been widely used as main girders in long-span bridges as a result of their high load-loading capacity, light weight, excellent aerodynamic, and speedy construction [1,2]. Cui et al [18] studied transverse residual stress relaxation in innovative both-side welded rib-to-deck joints of OSDs under constant amplitude cyclic loading. All of the existing literature investigates the uniaxial residual stress relaxation of simple welded joints under constant amplitude cyclic loading, but seems to lack information on the release behavior of multi-axial residual stress under variable cyclic loading at the heat-affected zone of complex DRWDs. In this paper, a FE analysis method is proposed to calculate the relaxation effect of the welding residual stress under the external cyclic loading of DRWDs in OSDs. First, a refined residual stress analysis model of DRWDs is established based on the element birth and death technology in the FE software ANSYS and the thermal-structure sequence coupling analysis method, and the initial distribution of transverse/longitudinal welding residual stresses are obtained. The Solid element, an eight-node hexahedral solid element, is used in FEM and its correci. 2021, 11, x FOR PEER REVIEW
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