Numerical Evaluation of Toe-Deck Fatigue in Orthotropic Steel Bridge Deck

Some toe-deck crack cases in China have been reported after about 10 years of service in suspension and beam bridge steel orthotropic decks with trough stiffeners. In this paper, a reference stress method used in design practice and a hot-spot stress method provided by the International Institute of Welding are used to investigate toe-deck fatigue of the newly built Taizhou Yangtze River Bridge. Shell and solid finite element models with different mesh sizes are compared. The hot spot at the weld toe and the point at the trough-deck intersection are discussed. One is a shell-model hot spot with no weld. The other is a solid-model hot spot with the weld. Hot-spot stress calculated with the shell model is larger than that with the solid model. Different extrapolation methods of hot-spot stress are discussed; stress calculated with the linear extrapolation method is almost the same as with the quadratic method. The stress of the joint under a moving unit wheel load is studied. Fatigue strengths against reference and hot-spot stresses are derived. Fatigue damages under the truck load, evaluated based on the reference stress method and the hot-spot stress method, are compared. (C) 2014 American Society of Civil Engineers.