Fatigue assessment of a long-span suspension bridge with an orthotropic deck in aluminium

A novel grain scale plasticity-based approach for multiaxial fatigue life assessment is introduced to evaluate the fatigue life of friction stir welded (FSW) joints of the aluminium orthotropic bridge girder of a long-span suspension bridge. The proposed method is validated using multiaxial fatigue tests on FSW specimens and random variable amplitude uniaxial loading tests on FSW and MIG welded joints. A framework for simulating the combined effect of stochastic traffic and wind loading on the considered suspension bridge is presented and the fatigue lives of eight selected details are calculated using the nominal stress, the critical plane method and the proposed grain scale plasticity-based model. The critical plane method provides the shortest fatigue life while the proposed model predicts the longest fatigue life, aligning with the findings from the experimental data used for validation of the proposed model.