Notre-Dame de Paris as a validation case to improve fire safety modelling in historic buildings

The analysis of the thermal damages in Notre-Dame de Paris is necessary to estimate the impact of the dramatic 2019 fire on the remaining structure prior to reconstruction. In doing so, the large amount of data being generated creates a benchmark environment to test the relevance of numerical fire models in the unconventional configuration of a medieval roof. While being an uncontrolled and complex configuration, it can provide insights regarding the relevance of numerical tools for fire risk assessment in historic buildings. Analysing the thermal degradation of the Lutetian limestone in a vault of the choir, experimental techniques are developed to track the in-depth maximum temperature profile reached during the fire. Numerical simulations of the fire development in the roof space then aim at replicating the observations through the evaluation of the heat flux impinging the vaults during the fire. These simulations are carried out using Fire Dynamic Simulator, which requires a large range of assumptions prior to any simulation regarding materials, geometry, meshing and scale. These assumptions are described and pave the way to a future sensitivity analysis to confront the upcoming outcomes of the simulations with the experimental observations

Measurement of Water Content in a Wood Sample by Terahertz Imaging

International audienc

Effect of compressive loading on the risk of spalling

Mechanical loading is an important parameter of spalling phenomenon likely to occur in concrete during heating. Several tests in laboratory have shown an increase of the risk of spalling in the compressed areas. In this study, a specific metallic frame has been developed to apply uniaxial and biaxial stresses on slabs during fire tests. Tests carried out on an ordinary concrete (fc28 = 37 MPa) exposed to ISO 834-1 temperature curve with several levels of uniaxial loading are presented. No spalling was observed when samples were loaded at 0, 5 and 10 MPa. In the opposite, spalling was observed when the compressive stress was increased to 15 MPa

Contactless Transient THz Temperature Imaging by Thermo-transmittance Technique on Semi-transparent Materials

International audienc

Strategies to challenge the simulation of confined fires

The numerical simulation of fires concerns an increasingly wide range of applications, among which archaeology. The Chauvet-Pont d’Arc Cave (France) presents thermal marks on some of its walls. These marks result from prehistorical fires and archaeologists would like to know their characteristics (fire location, mass of fuel, number of fires, etc) to make assumptions about their functions. Being impossible to carry out fires in the cave, combustion simulation is a suitable tool to discuss this question. However, simulating a fire in a confined geometry is still challenging and some inherent difficulties must be overcome. In that respect, we reproduced four experimental fires in a cave-like geometry. Four tepee-like hearths, composed of different initial wood masses (16, 32, 60 and 90 kg), were burnt in an underground quarry. Twenty-seven thermocouples measured the temperature in the cold and hot gas layers, as well as in the ceiling jet area. The measurements in the ceiling jet resulting from the 90 kg fire are successfully compared to the corrected Delichatsios correlations. In addition, the measured mass loss rate is compared to a tailored modeling for tepee hearths. We also propose three strategies to simulate the combustion process of the 90 kg hearth: (i) with a significant refinement in the ceiling jet area (approximately 1,500,000 cells) and the law of the wall, (ii) without refinement but with Newton’s law of cooling and (iii) without refinement but with simplifying assumptions and adjustments. While the first and third approaches provide meaningful results, the second case is found to be inconvenient for compartment fires. Based on experimental data, this study aims to give some keys to perform simulations of compartment fires (in tunnels, buildings, car parks, etc) and numerically approximate the combustion of wood

Literature review on the behaviour of UHPFRC at high temperature

The results of several experimental campaigns concerning eight Ultra High-Performance Fibre-Reinforced Concretes (UHPFRCs) carried out in different European industrial and university laboratories are presented and compared in this paper. In the temperature range from 20°C to 850°C the results concerning the compressive strength, the elastic modulus and the thermal strain are presented and analysed. The influence of the testing procedures is discussed as well (for instance, with/without pre-loading during the heating phase). Comparisons are made with the decay curves provided by EC 2, for both ordinary and high-performance concrete. The presentation of the mechanical properties is accompanied by suitable observations made during several fire-resistance tests on small structural members (slabs, columns and beams). The temperature-time curves adopted in the tests were the well-known curves ISO 834 and the Increased Hydrocarbon Temperature Curve (HCinc). Once more, the effectiveness of polypropylene fibres against the risk of spalling is confirmed by the rather extended family of UHPFRCs and by the various geometries of the specimens considered in this paper