This unique bridge is a perfect example of the new generation of slender structures with large spans that could be realized in a very short time.
Project description
The old bridge that connected the cantonal road to the Walo Bertschinger AG works yard in Ticino was no longer flood-proof and had to be replaced by a new bridge downstream. Taking advantage of the unique opportunity to be both client and contractor, WALO decided to use this bridge as a showcase for innovation, realizing a project that would hardly stand a chance in a public tender. The variant chosen consists of four girders prefabricated on site from 75 to 125 cm, connected by a 5 cm thick binder course, which also serves as the deck. The thickness of the deck is limited to 15 cm between the girders. The structure is a semi-integral jointless bridge with flexible transition plates connected to the deck. This filigree bridge blends perfectly into the landscape.
Durability and speed
High performance fiber reinforced concrete (UHPC) has much better mechanical properties than conventional concrete. This makes it possible to greatly reduce the amount of material used and obtain a slender structure. The upward bending of the beam resulted from the constraints of the height to be left for the flow and the height limitations imposed by the abutments.
Due to its extremely dense matrix, UHFB is up to 1000 times more resistant to external attack than conventional concrete. This eliminates not only the need for waterproofing, but also the need for maintenance over the life cycle of the structure. The semi-integral bridge with transition slabs attached to the deck avoids any joints and limits all possible causes of degradation.
The prefabrication of the girders on site solved the problems and costs associated with transportation (26 m long - 40 tons). In addition, it allowed the direct installation of all necessary piping and avoided any work in the riverbed. Guidance barriers were installed on the girders before lifting to avoid the use of scaffolding for the safety of the workers.
The 5 cm thick surface layer provides a monolithic connection with the girders, resistant to freeze-thaw and road traffic forces.
Special features
The chosen concept allowed the commissioning of a bridge in a very short construction period. It was therefore possible to assemble the girders on Friday evening, pour the roadway on Saturday and put the bridge into service on Monday after appropriate post-treatment.
This unique bridge is a perfect example of the new generation of slender structures with large spans that could be realized in a very short time.
