Residual stress relaxation at innovative both-side welded rib-to-deck joints under cyclic loading

Abstract

Innovative both-side welded rib-to-deck joints of orthotropic steel decks (OSDs) was developed to enhance the fatigue resistance and extend the service life of bridges. Compared with the conventional welded joints, the both-side welded joints are subjected to different weld residual stresses (WRS) and WRS relaxation (WRSR) due to the different welding processes. Properly assessing the WRS and WRSR is a prerequisite for predicting fatigue damage and service life of OSDs. This study presents a new method to analyze the WRSR in rib-to-deck welded joints under cyclic loading. The initial WRS at a both-side welded rib-to-deck joint was measured using an ultrasonic method and simulated using a sequentially-coupled thermo-mechanical finite element model. The model is validated against the test data, and then used to analyze the WRSR. The influence of cyclic stress amplitude and stress ratio on the WRSR is investigated. The WRS rapidly drops in the first cycle and then gradually deceases until stabilized after about 5 cycles. The magnitude of the WRSR increases with the stress amplitude and the stress ratio. Finally, a formula is derived to predict the WRSR based on the stress amplitude and stress ratio.