Work description:
The Loja Viaduct project, executed in the vicinity of the Granada town of Loja, is a structure designed to provide service to the new Antequera-Granada High-Speed Line. It is integrated into the Loja-Riofrío Bypass, which is an intervention on the already existing conventional railway layout that aims to adapt it to the standard parameters of High Speed in Spain. The promoter is the Administrator of Railway Infrastructures (ADIF) and the main contractor is Grupo Copisa, which subcontracts TECOZAM to build the bridge deck. The Loja Viaduct, of the double-track railway type, is a concrete structure with a single-cell box girder, continuous and with a constant depth. It has a total length of 580 meters distributed in 12 spans, with a standard span of 50 meters, a deck width of 14 meters and a maximum gauge of 35 metres.
Works done:
TECOZAM has built the viaduct deck using self-launching formwork (self-casting) with the exception of the last two spans, which have been executed using full-frame formwork due to the impossibility of continuing to use self-casting due to the existence, below the bridge, of the conventional railway track, still in service, which will be replaced by the variant to which this viaduct belongs.
Own singular resources:
To build the deck of the viaduct, the ZAMORA I auto-centre has been used, one of the three auto-centre that TECOZAM currently owns. This self-supporting formwork was designed and manufactured by the Norwegian company NRS-AS for the construction of the MERSEY GATEWAY viaduct (England) in 2017 and later, after being acquired by TECOZAM, it was used for the first time in Spain for the construction of this viaduct. It is a self-supporting formwork under deck, designed to build decks with spans of up to 70 meters, although for this viaduct it has been assembled in a smaller configuration, 130 meters long, given the characteristics of this structure (in full configuration the length is 157 meters). The auto shoring is supported by a temporary metal system, fixed to the shafts of the viaduct piers, which is made up of a pair of brackets on which the machine rests and a pair of props to the ground, whose mission is to lower the loads from the machine to the foundation, avoiding loading the pile for this task. The empty weight of the autoform, with the configuration used in this project, is about 850 tons. The deck is built at the corresponding level of concreting of the opening established by topography and, after finishing, the entire self-centering is lowered to the launch level, located about 30 centimeters below the previous level, to immediately proceed to open the crosswise machine and launch it longitudinally to the next opening, where it will be closed again and raised to the new level of concreting. All these maneuvers are carried out by means of a complex and powerful hydraulic system.
Yields:
A complete span construction cycle was achieved every three calendar weeks. The complete cycle consisted of lowering the autoform to the launching level, opening it, launching it to the next span, closing it, raising it to the concreting level, topographic adjustments, placement of passive reinforcement, placement of active reinforcement, placement of interior formwork (gables, top slab ), concreting (two: one for the lower slab and gables, and another for the upper slab) and stressing.
