Construction works for the variant of State Road No. 29 bypassing the town of Dego (SV), between km 120+000 and km 124+750 – Lot 1 and Lot 2.

Project objective

Our Company prepared the construction design on behalf of the two Contractors for the bypass of the town of Dego, in the Province of Savona.
Within the works related to Lot 2, the main structure was the viaduct over the Bormida River.
The viaduct design required a change in the construction typology compared to that originally envisaged by the contracting authority ANAS S.p.A.

Main works

Viaduct over the Bormida River
The detailed design was based on a comprehensive topographic survey and an in-depth geognostic investigation.
In particular, it was necessary to modify the span arrangement and the construction typology compared to the preliminary design developed by ANAS S.p.A.
The viaduct, with a total length of 300 m, was built with a constant pier spacing of 50.0 m, adopting a construction method that allowed erection of the deck without using mobile cranes due to the inaccessibility of the areas below for heavy vehicles.
The adopted structure is a composite steel–concrete system with twin CORTEN steel girders, launched incrementally (“pushed”) from the Savona-side abutment to form a continuous girder along the entire length.
Based on the results of the geognostic investigation, a differentiated foundation system was selected for piers and abutments according to local geostratigraphic and geotechnical conditions and the need to prevent scour phenomena at the piers adjacent to the riverbed.
Adoption of the new construction technique enabled completion of the structure in shorter times than originally envisaged, without significant cost increases.