Fatigue Behaviour of Closed Stiffener to Crossbeam Connections in Orthotropic Steel Bridge Decks

Abstract

This study concerns the behaviour of the closed stiffener (trough) to crossbeam connection in orthotropic steel bridge decks and in particular, the connection where a continuous closed stiffener passes through the crossbeam. For this connection, the crossbeam in-plane and out-of-plane behaviour is analysed. The nominal stresses for unit loads on the crossbeam, unit rotations of the connection and the deck bending are determined for locations that are relevant for fatigue. For these locations, the geometrical stress concentration factors are also determined. Traffic loads for fatigue from ENV 1991-3 (EN 1991-2) are simulated by maximum crossbeam load, connection rotation and deck bending moment intervals with equivalent numbers of cycles. By applying geometrical stress concentration factors to the nominal stresses the geometrical stresses are obtained. By scaling these geometrical stresses of the unit loads, rotations and deck bending moments, the resulting geometrical stress intervals are used for a fatigue assessment of an example crossbeam with three different types of connections: - Closed stiffener through a cut-out with a cope hole, - Closed stiffener through a close fitting cut-out, - Closed stiffener fitted between the crossbeams. The restraints generated by local bending in the deck and torsion in the closed stiffeners are analysed separately. The results of the calculations obtained by analytical models and FE models, are compared with measurements. Conclusions are drawn about the analytical models and the sensitivity of the analysed locations to fatigue cracks.