The new Dão Bridge is located on the 3rd main route (IP3) and crosses the existing Aguieira’s reservoir dam. The old bridge presented serious pathologies due to concrete internal expansive reactions, requiring, therefore, to be replaced.
The bridge superstructure consists of a continuous single-celled box girder deck 390m long with a central span of 170m. The deck is in prestressed concrete and was built by the balanced cantilever method with cast “in situ” segments of 5m long.
The two piers are twin flexible thin legs in reinforced prestressed concrete. Their deep foundations entailed, for each pier, the construction of nine piles, with a 2m diameter, that are well-grounded in a schist bed rock, which is almost superficial.
The foundation construction was especially critical and demanding due to the local implementation conditions. Thus, the adopted construction methodology required special fluvial means and featured a box caisson in reinforced concrete in order to allow a dry concreting of the piers pile cap.
The bridge was opened to traffic in August 2015 and the deck’s 4 x 17 segments construction took only 9 months.