A Probabilistic Approach to Wood Charring Rate

This report presents a probabilistic model for wood charring rate and an application of the model to assess fire resistance of a wooden load-bearing beam. The model is an empical one, based on quantification of the dependence of the wood charring rate on the principal physical factors governing the charring process. These factors include the influence of the heat flux exposing the wood surface, the wood density and moisture content as well as the ambient oxygen concentration. The application introduces a novel approach to assess the endurance of a wooden structural member in a natural fire conditions, which uses probabilistic fire simulation to quantify the heat exposure and the char depth of the structural member. The principal result of the approach is the time evolution of the conditional failure probability of failure of the structural wooden member, which can be further elaborated by incorporating into the analysis the statistical and modelling results determining the frequency of the conditioning factor, i.e., the occurrence of a fire with sufficient severity to potentially compromise the structural safety.