Authors: Jin Zhang ZengHui Liu YiXiang Xu ShuWei Ma QingFeng Xu
Publish Date: 2012/08/16
Volume: 55, Issue: 12, Pages: 3434-3444
Abstract
To investigate the charring rate of timber beams exposed to threeside fire a total of fifteen new and used DouglasFir timber beams in four groups exposed to threeside fire were experimentally studied together with the finite element analyses of the temperature distribution in the beam section The durations of fire exposure were 0 on a test piece 10 15 20 and 30 min according to the ISO 834 standard fire curve The charring depth of each timber beam was calculated by averaging the values at onethird and twothirds along each cross section to give the charring rate of timber beams It was found that the timber beam’s charring rate reduces as the duration of fire exposure increases and the vertical charring rate is slightly higher than the horizontal one The areas of beam sections reduce due to charring and the strength and stiffness of the pyrolysis layer near the charring edge decrease owing to the hightemperature The average horizontal and vertical charring rates are 098 and 108 mm/min respectively To take into account the difference between the test furnace temperature curve and the ISO 834 standard fire curve some corrections were made for these data to yield the solution for charring rate With the help of the finite element software ANSYS the temperature distribution of the wood’s crosssection was analyzed The longer the exposure time is the greater the effect of density will impose on the distribution of temperature but the moisture content has no effect
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