Canada bridge hangers replacement

Before Freyssinet’s intervention, the suspension bridge suffered from major structural defects on certain hangers which showed significant section losses.

Freyssinet was commissioned by the Côtes d’Armor Department to secure the structure in 2017, and then hangers replacement in 2018.

The existing hangers were made up of 40 metal wires 7 mm in diameter arranged parallel to form a rectangular section. Due to several wire breaks and an advanced general state of corrosion, the structure could not be adjusted without weakening the rest of the structure. It was therefore decided to replace the faulty hangers.

The works required consisted of identical hangers replacement. As this operation is very costly, Freyssinet proposed a technically reliable and economically advantageous alternative solution to replace the hangers.

The solution was to install two hangers in the place of an existing hanger, allowing the new hangers to be installed before the existing hangers were removed.

The existing hangers were made up of 40 metal wires 7 mm in diameter arranged parallel to form a rectangular section. Due to several wire breaks and an advanced general state of corrosion, the structure could not be adjusted without weakening the rest of the structure. It was therefore decided to replace the faulty hangers.

The works required the installation of scaffolding on the arches of the structure in order to access the upper part of the suspension. A detailed study was conducted before the commencement of work to best adapt access to the top of the structure in order to work in safety. The bridge was to remain open to traffic during most of the work, forcing the site crew to organise themselves methodically for the supply of the various materials. Only the installation of the hangers was carried out at night with interruption to traffic.

The installation of the new hangers required core drilling into the existing structure. As the structure was highly reinforced, it was necessary to install the cores very precisely so as not to damage the existing reinforcement.
To avoid damaging the existing structure, the new hangers were tensioned simultaneously on either half of the structure (2 tensionings – 36 hangers simultaneously), requiring perfect synchronisation of the site team.