During once in a millennium type storms, such as the 1999 storm, gusts of wind can reach 140 kph. Faced with these exceptional weather conditions, the client wished to have confirmation that this event had not had any structural impact on the roof of the Stade de France. The dynamic measurements made by the OSMOS sensors revealed that the oscillation frequency before, during and after the storm had not changed. Proof that no post or tie rod had been deformed beyond its elastic range. Installed as a predictive maintenance tool at the time of construction, the Optical Strands made it possible to optimise maintenance and assess the impact of non-standard events.