SUMMARYThis paper describes an experimental investigation of the charring rates of timber. An experimental procedure was designed for assessing the charring rate of 20 specimens exposed to fire in a single test, with one-dimensional heat transfer conditions.Each test specimen was manufactured by gluing seven laminates together. Four thermocouples were inserted at different depths in four different laminates located in the middle of the test specimen. The test was conducted using a gas-fired furnace and specimens were exposed to the standard ISO 834 fire.In order to evaluate the fire performance of tropical hardwoods, seven different species with densities ranging from 500 to 1000 kg/m 3 were used. For the purpose of verifying the experimental procedure against existing data, two softwood species (spruce and fir) and one European hardwood species (oak) were also examined.Experimental results indicate that the test method and procedure can be used for assessing the charring rate of timber both for softwood and for hardwood species. They also show that the density of wood significantly affects the charring rate and that the values recommended in Eurocode 5 for high densities are somewhat too conservative.
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.
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