G. Sarcina, F. Poltronieri, M. Raccagni, S. Dal Zotto, L. Sartori, V. Cardella, A. Morbin: Genoa San Giorgio Bridge – The realization of an iconic artifact
was also necessary for the reinforced concrete works to be carried out simultaneously in such a way as to give enough anticipation to the laying of the deck (Fig. 2). The Fincantieri Group used the sites in Valeggio sul Mincio (VR), Castellammare di Stabia (NA) and Sestri Ponente (GE) to produce the Genoa Bridge for the construction of the metal structures the deck was made of. Only through the preliminary analysis of the potential and skills of the individual sites was it possible to focus the objective of each plant and maximise productivity. The dressing elements of the macro elements and all the upper structures such as longitudinal beams, transverse elements and profiles were made, welded and checked at the production site Valeggio S/M equipped with automatic welding systems such as the T-Master, with tandem configuration, and manipulators with one and two opposing welding heads; the technologies used maximize the repeatability of the welding process, ensuring its quality. The macro elements that form the bottom of the deck were made in the shipyards of Castellammare di Stabia and Sestri Ponente with a bottom plate welded in a single solution through the use of automatic „Panel Line“ welding equipment, to then be structured with longitudinal beams and transverse stiffeners. In an equally strategic way, the pier elements, structural elements of considerable constructive complexity due to the presence of heavy stresses and welds of particular difficulty and size, were separated from in-line production. The decision to make the 18 pier segments as complete structural elements was fundamental to optimise construction times. After the completion of the geometric control activities and the execution of Non-Destructive Testing (NDT), the structural elements were painted with a highly durable C5 VH paint cycle in a very aggressive environment in accordance with UNI EN ISO 12994 – 2 and a decisive finishing colour wanted by the Architectural Management of RAL Design 220 80 05 with a surface gloss of 30 %. The macro elements made at the production sites of Castellammare di Stabia and Sestri Ponente were transported by barges across the Tyrrhenian Sea to the pier near the mouth of the Polcevera river (Fig. 3); once disembarked and positioned on particular multi-axle and high lift trailers, they
were transported to the construction site with big overnight transport vehicles. The maximum width of 10 m of the macro elements was analysed in the design phase to allow the particular transport method, performed with a few spare centimetres in relation to the passage areas. The entire metal deck has a total weight of about 17,500 tons of which about 77 % was processed at Valeggio S/M. Part of this material was delivered directly to the shipyard in Val Polcevera while 30 % was transported to the Naval production sites where the structural elements were welded to the metal sheets of the previously prepared keeled bottom. The construction and shipment of the 262 macro segments based on the management programme prepared and monitored daily was essential for respecting the project’s challenging implementation deadlines.
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Assembly and monitoring of the works
The spans were assembled starting from the calendered bottoms placed on provisional works on which each segment was progressively based with the diaphragms, main beams, side panels and, finally, the panels. The upper main beams were welded to the lower beams along with the bottom of the segment by means of longitudinal corner bead welding. The segments were subsequently welded together at full penetration before being moved to be raised. The joint preparation, preheating and welding control activities were supervised by the welding coordinators and checked upon completion of the same in accordance with the inspection plan with visual, magnetic and ultrasound methods. All the personnel used for welding activities on the ground and at height were in possession of licenses issued by the accredited third party Accredia. The upper transverse elements and the diaphragms were assembled by means of bolted joints using HRC bolts. This particular bolt allows the reduction of the tightening control times required by the standards to ensure the successful application of the tightening torque. All the movements of the segments and the macro elements of the spans were carried out with SPMT (Self Propelled Modular Transport) trolleys, in modules with 4 or 6 axes that can be assembled according to transport needs. The system offered great versatility in displacements and made it possible to move from the smallest macro-segments, weighing about ten tons, up to 100 m fully assembled spans of 1,800 tons (Fig. 4).
Fig. 3 Loading on barge of the macro blocks in Castellammare di Stabia (Naples)
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The construction site faced extremely adverse environmental conditions, with almost 100 days of hydrogeological weather alert from September 2019 to June 2020 with whole days of intense rain or strong wind. In addition to this, in a paroxysm of complications, the Covid19 pandemic exploded in Italy. The first strong containment countermeasures that almost stopped the nation were es-
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