Rehabilitation of St. Ursanne Railway Viaduct, Switzerland

The construction of the first curved viaduct to span the Maran valley in 1875 consisted of a steel truss bridge with six spans of 40 m resting on imposing masonry piers. The truss superstructure soon displayed weakness and traffic loads were continually increasing. Finally, the shift to electricity at the end of the 1920s accelerated the decision to renew the superstructure. The alternative selected was a complete transformation of the viaduct into a 12-vault concrete arched bridge. The refurbishment of a large viaduct was an opportunity to put in place an innovative method developed by the Swiss Federal Railway for the construction of a 270 m long deck in as little as three weeks. This method proved successful and represents an economical alternative to traditional methods. This is especially important since Swiss Federal Railways will be confronted with similar refurbishment projects in the future.