Montabliz Viaduct, Cantabria (Spain)

Located in the Cantabria Mountain Range, the Montabliz Viaduct forms part of the Meseta Motorway crossing the river Bisueña valley in a beautiful natural site with very rough terrain. Amongst the sixth highest built to date in Europe, this is a unique structure as demonstrated by its 145 m high pier (the highest in Spain), 175 m clear centre span and cross-section design using a single box section supporting both carriageways with a 26,1 m wide roadway. The viaduct's piers were built with self-climbing formwork, used for the first time in the construction of bridge piers in Spain. The cantilever system used in the in situ concrete deck construction was the result of the specific design and because the segments forming the deck girder are the largest and heaviest built in Spain to date and among the largest in the world. The viaduct's height and spans called for the structural response system to be statically and dynamically monitored in real time, both during construction and service life. As the wind force on the bridge was a determining factor in its design and had to be accurately defined, two wind tunnel tests were required, using three dimensional (3D) models reproducing both the actual geometry of the structure and of the valley where it is located.