Characterization of TRAvelling FIRes in large compartments

Inspection of information pertaining to fires in large compartments over recent two decades reveals them to have a great deal of non-uniformity. They generally burn locally and move across entire floor plates over a period of time. This phenomenon generates non-uniform temperatures and transient heating of the structure. A representation of this type of fire scenario is being established in the concept of a “travelling fire”.

The travelling fire models that exist in the literature neglect some important aspects of fire dynamics and furthermore, don’t consider the conditions in which such fires can develop. This project aims to define those conditions as well as to improve the characterization of a travelling fire: the fire trajectory, its spread rate as well as the temperatures it generates, in the near and in the far field. Travelling fire is a complex topic that is now being researched all over the world, but there is a consensus among the researchers that the main limitation is the lack of large scale test data.

In this work, small scale tests for which the fire dynamics are well controlled are first planned. They will allow evaluation of the influence of the flame depth and the fire load arrangement that comes as close as possible to values representative of an office building. Then, large scale tests will be performed in real building dimensions: the fire path and fire geometry will be observed, and the temperatures, heat fluxes and spread rates will be measured. These tests will be performed with less control over the dynamics. Indeed, they will be realized to be as realistic as possible, which will allow the characterization of the fire source and later, the calibration of numerical and analytical models.

Indeed, following the tests, numerical modelling using CFD will be performed in order to perform a parametric study covering the whole practical range of possible scenarios.This will serve as the basis for developing an analytical procedure which will characterize in an improved way the fire source, its spread rate and the temperatures fields it generates.

Then, the methodology will be introduced in the FEM software SAFIR and OpenSees in order to have a large utilisation of the proposed model in the construction market.

Finally, design guidance will be provided. It will be presented in a document which will provide a simplified version of the project scientific content, an easy to use method to characterise the thermal attack caused by travelling fire, and worked examples.

To conclude, this project about travelling fire will ensure: a safer fire design analysis for large compartments based on a thermal model which is as realistic as possible, safer conditions for occupants and rescue services, as making the steel structures more market competitive.

The research will lead to a travelling fire model for design which is relevant for large spaces in modern constructions which are in accordance with expectations of today’s society.

Ultimately, it will provide design offices with realistic and clear guidance as well as a user friendly model to apply this concept.

Many studies of fires in large compartments reveal that they do not burn uniformly throughout the enclosure. They tend to travel and lead to highly non-uniform temperatures which implies a transient heating of the structure. Travelling fires are not considered in the Eurocodes : the main limit in developping models is the lack of large scale, realistic test results. This project aims to realize such tests and performing numerical simulations to define the conditions in which travelling fires develop, to build an analytical model which evaluate the thermal effect and to create design guidance which improves structural safety.