Fatigue Performance Study Of The Orthotropic Steel Deck Based On Fracture Mechanics

Orthotropic steel deck has been widely used in steel bridges because of its light weight, low building height and high bearing capacity, etc. However, fatigue problems are prominently arisen from the combined effect of complex structure, numerous weld joints, and overloading. For the convenience to apply in engineering of fatigue crack residual life assessment, based on the fracture mechanics theory, and choosing the most important parameter-the stress intensity factor K, which has significant influence on the propagation of fatigue crack, the fatigue performance of the position of arc-shaped cutouts on diaphragms with the intersection of longitudinal ribs was studied. The thesis has basically accomplished five aspects as following:(1) The emergence, development process, geometry structure and mechanical characteristics of the orthotropic steel deck are elaborated, while the fatigue problems occurred during its development are introduced.(2) The development process and current situation of fatigue research on the orthotropic steel deck at home and abroad are dicribed; fatigue research by using common methods and means by using the fracture mechanics are introduced. At the same time, some current problems about fatigue research that our country faced are summarized.(3) Aimming at figuring out prominent fatigue problems of the orthotropic steel deck, the key point at the position of arc-shaped cutouts on diaphragms with the intersection of longitudinal ribs is selected to be studied, and a simulation analysis model is established to calculate the stress intensity factor K under different parameter combinations and crack length condition. After that, regression equation about K is got by using regression analysis.(4) By substituting the stress intensity factor K into the Paris formula, a curve of fatigue crack propagation has been acquired by numerical integration, and then some full-scale model tests are carried out to verify the reasonableness of this curve.(5) To provide a reference for practical application in engineering, a process for assessing the residual life assessment is established for the orthotropic steel deck under different parameter combinations.