Fatigue Life Prediction on Rib-to-Deck Welded Joints of Steel Bridge Deck Based on LEFM

In order to explore the fatigue performance of U-shaped rib-to-deck welded joints of orthotropic steel bridge deck under cyclic loading, based on linear elastic fracture mechanics (LEFM), fatigue life evaluation was carried out using finite element method (FEM). According to the structure features of rib-to-deck welded joints of orthotropic steel bridge deck, 2D FEM model with 3 U-shaped ribs was built using ANSYS software. Presetting 4 kinds of initial cracks for weld detail, the equivalent stress intensity factors (ESIF) at each crack with 2 loading cases were calculated. The relationship between stress intensity factor and influential parameters, including initial cracks length, thickness of deck plate, height and thickness of U-shaped rib, was analyzed. In accordance with weld detail category of orthotropic steel bridge deck in Eurocode 3, ESIF at every crack were obtained, and fatigue life prediction method of weld joint of orthotropic steel deck were proposed based on fatigue crack propagation model in LEFM theory. Results show that fatigue life calculated with LEFM is greater than the value in Eurocode 3, and fatigue life of the welded joint will be enhanced when the deck plate thickness is 16-18 mm and initial crack length is less than 0.1 mm.