09.16: Edge clamping effect on the fatigue resistance of an orthotropic steel bridge deck

Abstract

ABSTRACTOrthotropic steel decks are an excellent solution for long span bridges, except if the spreading of wheel loads through the pavement is poor. In the latter case they are heavily sensitive to fatigue cracking. The most critical locations of fatigue cracks are the connection of longitudinal stiffeners to the deck plate and the cutouts and cope‐holes in the webs of the transverse stiffeners. OSD with variable depth are seldom used, since the idea contradicts with one of the main assets to limit the bridge deck depth. However, in few cases variable depth may be meaningful as in the case of a railway bridge across river Dyle, recently built in Mechelen (Belgium). This 50 m span bridge consists of 2 lateral stubs of 1.55 m diameter connected by the OSD. The tubes are slightly bent to foster arch thrust action and rotated towards the bridge axis. In addition, the arch springs are encased in the concrete abutment. Due to this arrangement, the crossbeams are partially clamped in the lateral tubes of high torsion stiffness. The effect of the end clamping of crossbeams reduces the tension in the lower part of the crossbeam web, also near the outer cope holes, where the largest stress concentrations occur and fatigue resistance is the lowest. The reduction of the magnitude of these stress concentrations is significant and depends on the crossbeam span. However, the effect disappears if the crossbeam web is higher, thus confirming it is due to bending tension of the crossbeams. In addition, the influence length of crossbeams has been verified in the case of river Dyle bridge and complies well with Eurocode.