S. Miguel, Azores, Portugal
The Viaduct over the Espigão Stream is located in the 3.1 Stretch – Algarvia/Nordeste of the Expressway Concession on S. Miguel Island already mentioned in this publication. Due to the geodynamic environment, the S. Miguel Island, located at the intersection of three tectonic plates (Eurasian, African and North-American), is subjected to high seismicity, with tectonic and volcanic activity origin, almost permanent, sometimes with a very high microseisms intensity peaks. From the structural point of view the main peculiarities of this project resulted from the geomorphology of the valleys in which the main viaducts are set in, very deep, with very steep ridges, dense vegetation and difficult accesses, resulting in the need of minimizing the number of piers leading to a set of viaducts with large spans. These characteristics also conditioned, above all, the ability to carry out topographic surveys in the preliminary stages of the project, and geological assessment, which, in the end, revealed particularly difficult and heterogeneous foundation conditions even within the same valley. The structural solution is the same described for the Viaduct over the Caldeirões Stream resulting in 3 spans and a total length of 218,8m between abutments, comprising a middle span of 100,8m and 2 side spans of 59m.