The construction of the new Lisbon-Algarda rail connection requires the crossing of the Sado River, which flows into the Atlantic Ocean south of the capital.

The topographical characteristics of this alluvial valley require the construction of two approach viaducts of 1,115 m and 1,140 m and a bowstring bridge, which is a continuous structure consisting of 3 spans of 160 m each. 

In each span, the single-girder deck, capable of carrying two rail tracks, is supported by a central arch and vertical metal hangers, giving the whole a bowstring-type behaviour.
The particularity of this structure is in the hexagonal cross-section of the arches and the structural continuity of the deck between the three bridges.

The infrastructure of the complex, which is made of reinforced concrete, is based on piles and equipped with seismic load-absorbing devices.
The height of the piles varies from 4.5 m to 23 m.

SECO’s assignment consists of the technical inspection services of the design of the bowstring bridge and the approach viaducts.