Desing System
Accelerating construction: the Zandhazen
railway bridge’s swift assembly with Niobium-enhanced steel
Engineering excellence: the strategic
material choices of Zandhazen bridge
The decision to employ S460 steel over the lower-strength alternative, S355 (355 MPa), stemmed from practical constraints. Thicker plates would have been necessitated by S355 steel, contravening the maximum permissible thickness values outlined in EN 1993-1-10 standards. Since neither fatigue strength nor stiffness dictated the design of the main structural elements, the adoption of S460 proved technically feasible and yielded a significant weight reduction of approximately 30%.
As the Dutch Railway Authority, ProRail, specified that the S460 steel be thermomechanically rolled in order to improve weldability, a Niobium micro-alloyed steel alloy design was used. In addition, ProRail imposed tighter limits on carbon content, carbon equivalent, and yield to tensile strength ratio than that defined in the product standard EN 10025-4 and design standard Eurocode 3.
S355K2+N was used for the crossbeams of the deck section, in order to expedite repair works in the event of vehicular impact. In total, 8400 tonnes of steel were used in the bridge for the main girders, arch sections, hangers and cross beams, roughly equal to the quantity of steel used in the Eiffel Tower.
Overcoming challenges in the
Zandhazen railway bridge
The final design involved two arches which slope towards each other, connected by four horizontal couplings. These 50m high steel arches, with 25 diagonal hangers, make the long span possible without inducing excessive bending moments in the deck. This design concept ensures that the bridge behaves more like a lattice girder, and the greater stiffness leads to smaller deflections. The diagonal hangers, designed to carry axial compressive forces, are hollow steel tubes with a diameter of over 600mm. The use of tube sections, as opposed to cables, obviates the need for continuous tightening during construction.