Notre-Dame de Paris Cathedral is preparing to reopen its doors, five years after the fire of April 2019. The official ceremony takes place this Saturday, December 8, in the presence of President Emmanuel Macron and other heads of state foreigners. The public will be able to rediscover the building from Sunday, even if images of the interior have already been revealed. We discover a brighter and almost warm cathedral. What visitors will not see, however, is the new fire-fighting system located in the frame.
It is north of Paris, 70 kilometers from the cathedral Notre-Dame of Paristhat we have an appointment. Benjamin Truchot, head of the “Dispersion, fire, experimentation and modeling” unit at Ineris, welcomes us to his office. On his computer screen, a three-dimensional reproduction of the nave of Notre-Dame. “ THISa, this is the result of a digital simulation of the propagation of the fire in the nave of Notre-Dameexplains the engineer. And what you see in orange and black is the fire and the spread of the fire. »
In fact, it only takes one click to start the animation and observe the spread of the fire in the digital version. “ The objective is to see how quickly the fire spreads, how quickly it reaches the upper part, how it interacts with the ventilation and that, then, allows us to imagine the safety measures that will allow to curb the spread of fire and then test them », says Benjamin Truchot.
Full-scale test
This is the next step: testing the results of the simulation on a full-scale basis. For this, Benjamin Truchot takes us to a huge hangar, “ an experiment chamber, where all the fire experiments are carried out. »Here the frame of Notre-Dame has been reproduced identically, in a smaller version, which did not serve very long, and for good reason: “ We have reproduced on this frame a start identical to a fire which could start on the real frame. »
The experiment took place a few weeks ago. It demonstrated that the fire spreads as predicted by the computer simulation. Until suddenly dying out. Jean-Pierre Bertrand, technician at Ineris, supervised the test: “ It has been shown that after a fairly massive fire outbreak, the water mist was able to extinguish the start of the fire on the frame. “. The millions of micro-droplets sent by the water mist make it possible to reduce the ambient temperature and smother the flames by driving out the oxygen. Result, ” it is the water mist system which is installed today in the framework of the cathedral », explains Benjamin Truchot.
The modern at the service of history
The choice of water mist to fight a possible new fire is the conclusion of several months of work and a challenge: that of adapting the latest digital technologies to the needs of historic architecture, underlines Benjamin Truchot. “ This is the interest of modernity and scientific progress. It is modernity at the service of the reconstruction of a historic building. »
Jean-Pierre Bertrand sees another benefit in these weeks of experimentation. That of making your profession known. “ People understand the usefulness of my job. They understand that we are trying to strengthen security so that nothing happens the same way in the future.. »
Benjamin Truchot is more modest. “ There is a little touch of our touch at Notre-Dame, yes. » But if a new fire was contained more quickly, should we consider that it is also thanks to Ineris? “ Partly thanks to us, yes. » The engineer, however, makes a promise: this option will not happen.
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