The viaduct over the A-3002, N-I and Zadorra River, is part of the project: Vitoria - Bilbao - San Sebastian High-Speed Railway.
This viaduct has a total length of 463 meters, divided into six spans distributed as follows, 64.5 +2x85.5 +77.5 +85.5 +64.5 m. This longitudinal span scheme is conditioned by having to cross, with a large skew, the N-I, A-3002 and Zadorra River, involving spans of 85 m, rare in structures of high-speed railway. The fact that the deck serves to a two-way line, determines its width which raises the 14 m.
The deck is resolved by a hollow box section of pre-stressed concrete with a single cell and constant depth in all spans, except at pier support, where a linear variation of depth is planned, from the 3.00 m deck in the constant region to the 6.60 meters on the pier support.
On one hand, the Environmental Impact Statement did not allow the use of temporary supports in the river Zadorra, and on the other hand, crossing the N-I Highway should be carried out minimizing the affection to the heavy traffic. Therefore, the pre-stressed concrete box section was replaced in the mentioned crossing spans, by a composite section to ease its erection. These spans follow therefore a hybrid solution that combines in one structure the types of pre-stressed concrete and composite deck, in the main spans, which is entirely a new solution in rail infrastructure for high-speed lines.
The construction process consists in the execution of the concrete spans in phases, with complete span false-work for the deck, and erection of the composite spans with the help of cranes.