Bending of Converging Hangers in Steel Tied Arch Bridges

Two alternatives of hanger arrangement have been proposed for the new twin bridges, which constitute the crossing of the river Nete by the main railway lines from Brussels to Antwerp. The alternative with a fan arrangement of hangers concurring at a centre above the arch top was preferred. For steel railway bridges, deformations of the structure must be closely limited and fatigue resistance is an important issue. For this, closed section hangers have been used, and fatigue strength requires increasing the hanger cross section, bending moments appear at the hanger nodes. This frame effect and the bending moments in the hangers may be of the same magnitude as in the lower chord. Further increasing of the hanger stiffness, introduces even larger bending. At least for the case of the river Nete crossings, an optimal combination of node and hanger reinforcing was obtained, by a short and discrete node reinforcement. This solution has been implemented successfully and the construction by launching of the twin bridges is now in progress.