Design and construction of two integral bridges for the runway of Milan Malpensa Airport

In this study, two bridges recently completed at the Malpensa Airport are presented. The bridges overpass the trench where the railway track from Malpensa Airport runs to the city of Milan. They are part of a U-shaped path, called the hotel (H) ring, which connects the southern ends of the two existing taxiways. Such a crossing had to: (a) intersect the railway track twice with a high skew angle, (b) carry the maximum aeronautical loads, corresponding to the gears of an AIRBUS 380 aircraft and (c) host a 60-m wide taxiway strip, plus a lateral safety lane and a service road, for a total width of 96 m. For a bridge operating in such an environment, it was imperative to reduce inspections and maintenance activities to a minimum. Therefore, the designers excluded any detail arrangements or auxiliary devices having life-cycle performances much shorter than that of the main structure. In particular, expansion joints and movable or deformable bearing supports were excluded. Such constraints led to design two structures having the peculiar features that characterise them as integral bridges. This paper will firstly recall the aeronautical and railway specifications and the other operating constraints that characterised the design. In the second part, the criteria followed in designing the foundations, the abutments and the deck are presented. The structural analyses were set out in accordance to the sequence of the construction stages. For the bridge in its service configuration, self-weight and permanent loads give rise to a set of internal forces typical of a portal frame, while the localised loads, due to the aircraft gears, induce bubble deformed shapes characterised by particular transversal load distribution mechanisms. Details of completions and finishing works are finally given.