A DUPLEX ARCH FOR THE NEW MALIZIA BRIDGE IN SIENA The project for the reconstruction of the Malizia bridge arose both from the need to improve the flow of traffic and that of inserting an element into the landscape which was architecturally qualifying for the town of Siena (Fig. 1). A functional and technologically innovative solution for a bridge which will cross over the vast railway seat below was found in the construction of a large arch, positioned between the two previously built carriageways (Fig. 2). Uranus 35N duplex stainless steel was chosen for the construction of the arch, made up of 5 segments of welded tube, with an external diameter of 820 mm, obtained from plates with a thickness of 35 mm and width of 2,480 mm, supplied simply pickled. The segment tubes of the arch, each 10,700 mm long, were brake formed and joined longitudinally by submerged arc welding. A second brake forming process gave the elements their correct curvature. Lastly, the connections for the hangers were then inserted and welded (Fig. 3). The external surface was shot-blasted using grit and protected by means of adhesive plastic. The five elements were pre-assembled (with welding) on site and subsequently hoisted onto a temporary pier (Fig. 4). After the geometry of the structure had been checked, the final welds were carried out. The joints made on site were obtained by means of electrode welding (Fig. 5). Once assembly was complete, any damaged or welded parts were repaired on site, again using shot-blasting. The arch and the deck were finally connected by means of hangers.

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• Industeel

• Alloy Steel

• Bridge

• Duplex Stainless

• Article