The complexity of the project was quite considerable:
- The existing structures had to remain in operation for the duration of the works.
- Systematic use of pre-fabricated elements to widen the bridge, because it was virtually impossible to set up the formwork for the reinforced concrete structural elements above the Moselle river bed.
This concerned the following elements:
- Formwork base pre-slabs for piers and abutments.
- Shells for pier and abutment formwork, and support of cladding stones recovered from the existing structure.
- Pre-fabricated archways
Presence of numerous networks on Rue de la Garde and for the Pucelles slab, resulting in thin slabs and comprising large depressions and openings. Metallic brackets for the walkway, with widely varying distances and geometries. Balancing slabs for these same brackets with flat geometry and thicknesses that vary considerably.
Due to these technical complexities it was necessary to use complex calculation methods:
- Overall 3D modelling of the bridge, taking into account the thermal gradient and shrinkage gradient. Phased calculations taking into account mechanical properties of the concrete, the micro-piles, the piles and also the short and medium-term geotechnical parameters.
- Systematic modelling of all the slab studs (Rue de la Garde and Vestige des Pucelles).