The Viaduct over the Arade River stands out for being one of the few Viaducts in Portugal Mainland whose deck consists of a single-celled box post-tensioned prestressed concrete girder, with precast segments and built by the cantilever method with a launching girder. The prestressing was applied in the longitudinal direction. The constructor’s experience in this kind of engineering structures may be regarded as the main reason for this design option.
The bridge is located in the Lagos/Lagoa stretch of IC4 (A22), between the km 23+865 and the km 24+415. The deck, with 550m long, consists of 7 spans, with 5 middle spans of 96m and side spans of 35m.
The twin blade piers in reinforced concrete reach heights of about 15m above the ground. The abutments have typical configuration. Both shallow and deep foundations were used, the latter being applied only on the alluvial soil of the Arade River.