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Bridge over the Tagus River in Carregado

The New Tagus Crossing in Carregado is about 12 km long. It comprises the North Viaduct, with about 1700 m in length, the Bridge over the Tagus River with 970 m, crossing the smaller bed, and the South Viaduct with about 9300 m.

This project was co-authored with Coba, Civilser and Arcadis, with PC&A being responsible for the Bridge project.


The deck platform accommodates the transverse profile of the motorway with 2x3 lanes, comprising in each direction half a central separator with 0.3 m wide, an inner berm with 0.50 m, three traffic lanes with 3.50 m each, external berm with 2.525 m and service walkways, with 1.15 m, resulting in a platform with a total width of 29.95 m.


The North Viaduct, with a total length of 1695 m, is made up of four viaducts with beamed slab decks cast in situ, with current spans of 33 m and 2.0 m in height, monolithically connected to pillars/piles measuring 1.5 m in height. diameter. In the area of Viaduct V3 there is a span of 62.00 m for the crossing of the North Line, with the adjacent spans of 44.90 m. This crossing is carried out by the lower closing of each pair of beams, thus constituting a double box of variable height up to a maximum of 3.0 m next to the pillars adjacent to the railway line.


The South Viaduct consists of a set of twenty-two viaducts, totaling 9230 m in length, with decks in slab beams in reinforced and longitudinally pre-stressed concrete, with a current span of 36 m, monolithic with pillars/pile of 1.50 m in diameter that locally reach more than 50 m in depth. The decks were built using prefabricated box beams, on which the upper slab was concreted, using collaborating pre-slabs for this purpose.

The bridge has a total length of 970 m, divided into partial spans of 95 127 133 4 x 130 95 m, with a single deck in a single-cell pre-stressed reinforced concrete box, with a height varying between 8.00 m in the support at 4 .0 m in the middle span and next to the transition pillars. The coffin is equipped with large lateral consoles that are supported by metallic struts that discharge into the bottom slab of the coffin; its spacing is constant and equal to 5.00 m.


The deck is longitudinally prestressed by internal and external prestressing cables. Transversely, the slab is also prestressed.


Columns P1 to P5 are monolithic with the deck, consisting of two 1.20 m thick reinforced concrete sheets spaced 5.00 m apart. Each of these blades is in turn divided into two by a one meter long central void.


Pillars P6 and P7 are formally identical to the others; the spacing between slats is 7.40 m, which are equipped with a 2.0 m thick header slab, where the longitudinal sliding support devices are installed.


The foundations are indirect by piles of 2.20 m in diameter that reach more than 40 meters in depth. In columns P3 to P7 there are eight piles and ten in columns P1 and P2. The piles were made with integral metal casing.


The pile headers are large elements. There are two types of massive: those of pillars P1 and P2 with a thickness of 7.22 m and 33 m in width, in the area of the navigation channel, and those of the remaining pillars with 4.52 m in thickness and 27.5 m in width. In plan, these massifs have a rectangular shape topped by circular tops, which gives them less resistance to flow.

The transition pillars consist of a stirrup beam sized to accommodate the supports of both the bridge and the adjacent viaducts. This stirrup beam rests on four hollow hexagonal shafts. The foundation consists of a massive reinforced concrete header that connects ten piles of 1.5 m in diameter executed using a methodology similar to the piles of the adjacent viaducts.

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