Charring rate of wood for ASTM E 119 exposure

2008

Fire and Materials

SUMMARYEurocode 5, Part 1-2, presents several models for the calculation of fire resistance of timber structures. These models are based on the hypothesis that for temperatures above 300 • C, wood is no longer able to sustain any stress, which makes the determination of the location of the 300 • C isotherm decisive for the result provided by the models. In this paper, the charring rate model and the conductive model presented in Eurocode 5, Part 1-2 are compared regarding the determination of the location of the 300 • C isotherm. The main wood parameters investigated are density, moisture content and anisotropy. The almost complete independence of the charring rate model from these parameters leads to some inconsistencies between the models. To reduce these inconsistencies some proposals to improve the conductive and the charring rate models are presented.

Section: Influence Of Densitysupporting

confidence: 86%

Comparison between the charring rate model and the conductive model of Eurocode 5

Cachim

2008

Fire and Materials

“…The fact that the charring rate changes with wood density has been demonstrated by several authors from several countries [3][4][5][6] . However, this dependency is only marginally considered in the charring rate models of EC5 as shown in Table 1.…”

Section: Influence Of Densitymentioning

confidence: 99%

“…The charring rate of wood is proven to be dependent on moisture content as was demonstrated, for example by [3][4][14][15] . EC5 specific heat and density ratio curves were defined for service class 1, which means water content around 0.12.…”

Section: Influence Of Moisturementioning

confidence: 99%

Assessment of Eurocode 5 Charring Rate Calculation Methods

Cachim

2009

Fire Technol

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.

“…The charring rate of both softwood or hardwood timber exposed to the standard time-temperature curve [1,2] has been studied in United States [4][5][6], Sweden [7], Australia [8], New Zealand [9] and Malaysia [10]. All these investigations show that the density of wood has a major influence on this characteristic but tropical species have hardly been considered in these research works.…”

Section: Literature Backgroundmentioning

confidence: 99%

“…König and Waleij [7], for example, proposed to define a basic charring rate as the charring rate corresponding to one-dimensional heat transfer conditions. Several empirical models have been developed [4][5][6]. One of these and two methods proposed in standards currently used for fire design of timber construction have been compared with the experimental results obtained in this study.…”

Section: Literature Backgroundmentioning

confidence: 99%

Fire resistance of timbers from tropical countries and comparison of experimental charring rates with various models

Njankouo

Dotreppe

Construction and Building Materials

2005

Tropical hardwood species are more and more used in the field of construction due to the particular qualities they can offer. Presently it is no longer possible to envisage the development of construction materials and products without taking into consideration the problem of their fire behaviour, and more particularly of their fire resistance. In the case of timber elements, this characteristic is mainly influenced by the charring rate of the external layers of the element. On the other hand this parameter is influenced by the density of the material.Limited information is available on the charring rate of tropical hardwood species. Therefore experimental investigations have been conducted at the University of Liege to study this characteristic. Seven tropical and three timber species from temperate countries have been examined. Two types of test have been used, one on small specimens, the other on a construction element made of one single material. In the first type, 20 specimens have been manufactured by gluing several laminates together. The specimens were instrumented with four thermocouples inserted at various depths in four different laminates. In the second type, a non-loaded wall made of 12 glued-laminated spruce beam profiles was instrumented with thermocouples embedded at different depths in the panel for the evaluation of the charring rate.