The Mollet Railway Interchange has a major role in the European freight railway network. The interchange includes four railway viaducts: E2, E3, E7 and E8. The first three structures consist of a reinforced concrete deck supported by two precast concrete U-girders. The lengths of the structures are 719 ft (219.2 m), 471 ft (143.7 m) and 2,114 ft (644.3 m), respectively.
E8 allows the crossing of a railway intersection over two major tollways. This structure is a steel bridge with an X-shaped plan view. The bridge is 1,092 ft (333 m) long with a maximum span of 181 ft (55 m). It consists of a steel box girder with a top concrete slab of variable depth.
The superstructure is designed with double composite action and includes a bottom concrete slab in negative bending moment regions. This allows for the reduction of the steel quantities and the increase in ductility.
All foundations consist of 5ft (1.50 m) CIDH piles.
A detailed track-bridge interaction was performed to assess the behavior of the track-bridge system under live loads. This non-linear analysis avoided the placement of track expansion joints on the first three structures despite their length. The structure E8, given its length and complex shape, required the location of a fixed point on the substructure at the smaller abutment, in order to support the braking/acceleration and seismic loads. All non-fixed supports were defined as sliding POT bearings.
The complexity of the structures geometry (E8 in particular) and their interaction with the heavy traffic roadways underneath required a careful approach in terms of construction planning and scheduling. These requirements were considered during the design phase in order to correctly assess the long time-dependent concrete effects (creep and shrinkage).