The Alpes-Maritimes departmental administrative centre in Nice is home to the region’s facilities management services. The building complex was inaugurated in 1982 and comprises 20 cube-shaped “bubbles” that are superimposed in pairs with a cantilevered design. The complex started showing signs of ageing with the floor level at the far end of each bubble dropping by some 14 cm.

  • Name of the owner and client
    Alpes-Maritimes Departmental Council
  • Delivery date
    October 2012
  • Partners of the project
    Consortium including an architectural firm: SARL Stanislas Chevalier & Gilles Triquenot
    Co-contractor: STS Côte d’Azur

Emergency work to make the “bubbles” safe

Even before work started on the project, the authorities decided to evacuate 1,000 employees from the 10 “bubbles” on the east side of the building late 2010 due to fears that the facade elements might break away from the main structure. Employees were moved down to the ground floors so that they could continue working. Freyssinet was asked to provide emergency repairs to make the buildings safe. After working nights and weekends, our 50-strong team rolled out three complementary processes in less than two weeks, including tie rods within each floor to link the columns to the floor slabs, fitting mechanically welded cradles to reinforce the bearings for the walkways connecting the “bubbles” to the central section, and shoring up the floor bearings.

Stopping creep in the floor slabs

After our consulting team had completed a three-month investigations phase, the main work began on strengthening the building. To prevent further creep in the lower floor slab, which was causing the upper floors to drop and the structural columns to come free, Freyssinet reduced the cantilever of the “bubbles” by installing beams and struts under the lower floors using dry process shotcrete. The connections between the floor slabs and columns were strengthened by fixing ringed braids and fitting carbon fibre fabric strips from the Foreva® TFC® range. Finally, the damaged concrete linking the floors to the central sections was replaced with a stronger concrete mix.

  • 14
    Maximum deflection of the floor nosings (cm)
  • 2,408
    Number of ringed braids used
  • 1,050
    Surface area of the carbon fibre reinforcing strips used (m²)
  • 880
    Amount of dry process shotcrete (tons)

Activities as usual during the repair work

While the teams were urgently making the premises safe and later when carrying out the final strengthening work, the client wanted to keep the buildings’ ground floors open to the public (beneath the “bubbles”). To keep employees and users safe while work was in progress, Freyssinet proposed and installed a wide array of safety devices, including secure access tunnels to the buildings and debris netting.Special measures were also taken to tackle sound pollution, such as addressing all noise sources and reserving specific time periods for carrying out the noisiest activities.

The structural reinforcements that we fitted to stabilise the floors were designed to be as discreet as possible. They have helped safeguard the building’s ethereal appearance while maintaining the avant-gardist design of architects Honoré Toscan and Michel Mosser.

Works Group Leader, Building Agency – Freyssinet France