The Viaduct over the Longra River has a total length, between abutments axes, of 502,0 m (46,6 + 7×58,4 + 46,6). The platform is divided into two decks, materialising two independent structures, of similar characteristics. Each deck has a total width of 14,05 m, including traffic lanes, shoulders and walkways.
The designed solution was developed in line with the contractor ’s request for a concrete box girder solution, executed with an inferior movable scaffolding system, with a span not superior to 60 m. The decks are continuous reinforced concrete structures, longitudinally pre-stressed, using post-tension cables.
Each deck is formed by a concrete box girder with a constant height of 3,40 m. It presents a width at the base of 5,20 m, increasing linearly up to 7,20 m at the top slab. At the supports, columns and abutments, the concrete box girder presents a diaphragm, with 1,20 m thickness. The diaphragms have a fairly large opening, to allow the movement of the inner box girder formwork system, from one span to another.
Each deck is supported by the abutments, in the extremities, and columns in the remaining alignments, always with the use of bearing devices. In the abutments, in addition to the bearings for vertical loads, there were installed anti-seismic devices.
Each deck construction was processed in sequence, span after span, using a movable scaffolding system. The deck concreting joints are located at 11,6 m of the column axes, corresponding to approximately 1/5 of the span.
There is one column in each deck, equal for all alignments and both decks. The column has a constant section from base to top. It’s an octagonal hollow polygonal section, but not far from a rectangle. Its dimensions are 2,50m x 5,40m (dimensions of involving exterior rectangle) and 0,40m thickness. In the central zone of the valley, the columns have heights above 50,0 m. The foundations are materialised by individual footing or piles cap for each column, depending on the terrain’s resistance conditions.