Motorway viaduct over SBB line, Bülach

The deck slab of the busy motorway bridge near Bülach, Switzerland, exhibited severely inadequate calculated fatigue resistance. The standard-compliant fatigue verification could not be verified mathematically, even using detailed static models. To determine the actual fatigue stress, enertec engineering ag developed a measurement concept. The stress in the reinforcement from permanent loads was measured with MME at selected points on the underside of the carriageway slab. Furthermore, the stress changes in the reinforcement and the changes in crack width were measured when lorries drove over it for three months and during individual load tests. The measurement results were used to carry out a service life analysis. Taking into account past and future traffic development, the fatigue safety of the carriageway slab was verified for the planned remaining service life. The client and users were spared the need for complex and expensive reinforcement.