Stress concentration in steel bridge orthotropic decks

The structural behaviour of orthotropic steel decks is characterized by the complex interaction between its components (deck plate, ribs and floorbeams) and also by the interaction between the structure, the pavement and the vehicle's wheels tyres. Stress concentration resulting from out-of-plane bending of deck components at typical welded joints can make these structures quite susceptible to traffic-induced fatigue cracks. This paper addresses some of these issues through numerical modeling of orthotropic decks with trapezoidal closed ribs, via finite element method and elastic analysis of the structure under heavy vehicle wheel loading. The numerical model was calibrated with experimental results obtained from laboratory tests on a deck model. The obtained numerical results lead to a better understanding of the complex structural behaviour of slender orthotropic decks, with emphasis on the stress distribution and concentration at the rib to deck plate welded connection. A parametric analysis was performed to determine possible and rational combinations of the geometric parameters leading to the lowest values of stress peaks and the best consequent fatigue performance of the focused welded connection. Hence, the overall output can be addressed towards a safe and rational design as far as fatigue life is concerned.