Assessment of Eurocode 5 Charring Rate Calculation Methods

The basic hypothesis for the assessment of fire resistance of wood structures is that for temperatures above 300 oC, wood is no longer able to sustain any load. Consequently, the determination of the location of the 300 oC isotherm, the charring depth, is decisive for the result of fire resistance calculation methods. Charring rate of wood is dependent of numerous factors, such as wood species (density, permeability or composition), moisture or direction of burning (along or across the grain). Eurocode 5, Part 1-2, presents several methods for the calculation of fire resistance of timber structures that are divided into simplified and advanced. In this paper simplified and advanced methods are compared regarding the calculation of the charring depth. Finite element simulations have been performed, using the proposed wood properties of Eurocode 5 using finite element code SAFIR. The influence of parameters such as wood density, moisture or anisotropy has been investigated. The results obtained with finite element calculations were then compared with Eurocode 5 simplified models. Some inconsistencies between methods have been observed. This paper presents proposals to overcome some of the inconsistencies as well as to extend the applicability of the models.