FIRE RISK IN HISTORICAL BUILDINGS. THE CASE STUDY OF THE ARSON OF A SAVOY RESIDENCE DURING RESTORATION WORKS

摘要

The fire that destroyed a tower in the Savoy residence in Moncalieri, Turin, Italy, on 5 April 2008 isdescribed in this paper. The results of the field inquiry made it possible to describe the fire dynamics. The firestarted from a very interesting char combustion which was ignited from restoration works on a wooden floor.The works were suspended at 16.30 pm and the fire was observed at 5.00 a.m. from the town outside the castle.Char combustion occurred in the space between the false ceiling on the 3rd floor and the floor above. Thestructure was made completely of wood.Transition to flaming combustion occurred when the ambient on the fourth floor was heated by the charcombustion, which quickly led to the flames spreading to the 4th floor ambient. Vertical spreading was alsofacilitated by vertical walls made of a wooded structure filled with bamboo. The flames thus spread to the attic,where they then spread to the roof structure. No continuity solution in the wood structure was found at thislevel.In order to verify the assumptions and the fire hypothesis made on the basis of the investigation, a CFD firedynamics simulation has been performed using FDS 5. the simulation input data has been derived from fieldobservations and specialized literature. A three-stage simulation has been conducted to deal with the complexmechanism of fire dynamics in this situation, where each fire step takes input data from the previous. Thisapproach also makes it possible to avoid the calculation of steady times, which were not useful to represent theevolution of the fire. Three main phases, each characterized by precise behaviour, have been identified andsimulated for a suitable time to be able to characterize their evolution and the transition to the following phase.The three main phases were: a) smouldering combustion, b) flaming combustion with surface flame spreadingand c) general involvement of the main compartment. During the activities the authors also investigated thereduction of the fire risk by fire detectors in order to understand whereas, in this particular case, suchprevention measures would have significatively changed the evolution of the fire.