Earthquake reinforcement protection for Collège Dillon, Martinique

Collège Dillon is a school establishment built in the early 70’s. It comprises 4 buildings all of which received the same earthquake reinforcement. An earthquake hit Martinique on 29 November 2007 at 3 pm (local time). Of a magnitude of 7.3 at a depth of 152 km, this earthquake damaged Collège Dillon. The intensity at the level of Collège Dillon was qualified as degree IV on the MSK scale. The building was built without applying earthquake protection rules. No bracing system is present in the longitudinal direction. The expansion joint was not sufficient to ensure both parts of the structure would not come into contact. In addition, most bracket ends are deteriorated with a risk of concrete pieces falling down. The building was reinforced by means of a metal triangulated system. This system called “metal stools” is a 3D structure introduced into the building and having its own foundations (single pile at the location of each support). All the solicitations generated by an earthquake are borne by the new metal stools. It was necessary to create breaches at the level of the existing slabs to enable implementation of metal elements. Efficient transmission of stress between the metal structure and existing reinforced concrete floors was provided by putting in place over-reinforced concrete at the level of these local pockets, thus preventing the concrete from being crushed. In addition, pre-stressing and post-tensioning under the floor on every storey enabled uniform compression of the horizontal diaphragm. The studies were carried out under the direction of Professor Victor Davidovici.