ABSTRACT

The aging of the structures, together with the new seismic design guidelines, brings the Autostrada Torino Savona S.p.A. to investigate and control with more details the viaducts and bridges along the highway. One of the peculiarity of this motorway is that was built in three different stages, from 1960 to 2000, and it crosses a very rough path with different climate from mountains to sea area.

In this paper is presented the seismic analysis, structure vulnerability and the design solution applied to the structural rehabilitation of the one of the most important viaduct: Generale Franco Romano, located near Fossano in Cuneo district.

The bridge was designed in 1968 by famous bridge Engineer Silvano Zorzi (1921–1994) and it is the most significant structure of the highway. It crosses the Stura di Demonte river, with a total length of 2317 m with variable height from 30 to 85 m. The particular structural scheme of the bridge consists in multiple asymmetrical frames in prestressed concrete. The viaduct is composed of 52 spans with 45 m length and 12.3 m width. The static scheme defined a hyperstatic system between piers/decks. It is important to underlain that the structure was not designed with seismic loads.

The first part of the paper describes in details the innovative way of construction and unusually structure solution for those year together with the studies of the seismic risk assessment applied. The critical situations detected in the dynamic analysis, in particular to the connection between pier/deck and longitudinal beams close to the expansion joints, are presented. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315207681/cd556cd4-4dcf-4efe-8e29-56fc67b8bfbd/content/pg456_1.jpg"/>

The second part describes the strengthening design solution defined to solve the problems together the cost/benefits studies that are performed to define the best seismic retrofitting in according with economic budget and out of service of the highway during the work.