This building of the Fondation Louis Vuitton which was just inaugurated is situated in the Bois de Boulogne, a huge park west of Paris. Frank Gehry, its architect, wanted a building which looked like a sailing vessel. Its concrete structures inside, in fact called icebergs, thus support glass sails. One specificity is that those sails are higher than the trees in the Bois de Boulogne so they are quite exposed to the wind. The area covered by those sails represents more than 13,000 square meters, the biggest sail being about 3,000 square meters, so that represents an area as large as 5 to 6 soccer fields, and they can be as high as 70 meters above ground! So it was necessary to study how well those sails would resist to the wind. They are connected to the ground by pylons called tripods, to the concrete structure inside. The main risk is the damage that the wind can cause to the sails and to their support system It is necessary to anticipate and calculate those risks very precisely, especially in case of wind bursts. In this area of Paris, wind usually comes from the west. As I said, those sails are very high and so they are exposed to the wind. In case of bursts, winds can go as fast as 120km per hour, so that is already quite a storm! We are talking of 90km per hour on average and 180km per hour when there are bursts: it could break a sail. <i>What was the novelty of this project?</i> The novelty is first the size of the sails. A building with sails like this had never been built before. Its geometry is quite complex, the architect Frank Gehry and his team have developed special technical tools for it. The novelty first comes from this aspect of the building, which the company Vinci took in charge. Another novelty according to me on such a building is that we have simulated with a statistical approach the effects of wind bursts on the building over time. We have simulated about 2 hours of storm on the building, and of course we were focusing on the maximum risk that we observed. To do this, we needed to collect aerodynamic data that we obtained first on a model we made. To do the calculations, we needed to develop a method which would work for an industrial environment, as we were working hand in hand with Vinci on that project. The problem of working with an industrial partner is that you have to deal fast with a lot of data. We had to invent a way to compress the data in order to do the calculations as fast as needed. Fast and well obviously! Compressing the data is a bit like compressing a video file: you have codecs, and you have a kind of algorithm which compresses them. This enabled us to do the calculations faster and to do them for every possible scenario. On such a building, the wind can come from any direction. In this area, wind usually comes from the west, but wind can also come from east or north, so we did our calculations for 36 different scenarios for the whole building. Each sail has to be treated specifically according to its exposure, so everything has been calculated 36 times! In the future, the methods we developed for the Fondation Louis Vuitton will be useful both for the researchers as well as Vinci and other firms which worked on the building. This building was already very complex, but we can do even better next time: architects are never short of ideas, I trust them to design even larger buildings, always more complex!