Fire design of timber slabs made of hollow core elements

The fire design of timber structures usually take into account both the loss in cross-section due to charring of wood and the temperature-dependent reduction of strength and stiffness of the Uncharred residual cross-section. The fire behaviour of timber assemblies made of hollow core elements is characterised by different charring phases. After the fire exposed timber layer is completely charred and the charlayer has fallen off, the thin vertical timber members are exposed to fire on 3 sides, leading to very irregular residual cross-sections with charring depths much greater than for heavy timber structures. Based on an extensive experimental and parametric study, a simplified calculation model for the fire resistance of timber slabs made of hollow core elements has been developed. The calculation model bases on the reduced cross-section method and takes into account two different charring phases. The paper first describes and discusses the simplified calculation model, and then compares the test results to the calculation model. (C) 2008 Elsevier Ltd. All rights reserved.