Swivel Lowering Operation of the Viaduct over the River Tera

The deck is a concrete box girder which shall be launched from one the abutments and has a total length of 645 m. It is simply supported on concrete piers spaced 75 m. However, because of the wide riverbed, one of the theoretical piers has been replaced by a pair of inclined steel semi-arches. These semi-arches are joined at their upper end so they provide the support that the deck needs. At their lower end they are fixed to the foundation of that adjacent concrete piers. A distinct feature of this viaduct lies in the special construction method used for the erection of the inclined semi-arches: they have been lifted into a vertical position and, by means of a swivel lowering operation and external cables, erected and joined at their upper end. This method involved the provision of pins at the base of the semi-arches. In addition, the hinges were designed to be able to allow the adjustment of the semi-arches during the final phase of the erection.