A performance based two step numerical model to determine the behaviour of timber beam exposed to fire is presented. The first step is based on the coupled heat and moisture transfer model. In the second step, the newly developed mechanical model is given which enables to determine the mechanical response of timber beam simultaneously exposed to mechanical and fire load. Based on the model validation for standard fire exposure it was concluded, that a two phase numerical model appropriately simulates the behaviour of timber beam in fire. Furthermore, parametric study revealed that different levels of initial moisture content have a considerable influence on the temperature distribution, charring depth progression and mechanical response of timber beam in fire. In addition, it was presented that the use of simple Heat model based on the Fourier partial differential equation is limited since only one moisture state of timber can be accounted for. The average charring rates for standard fire exposure and at different initial moisture contents are given as well. The possible range of charring rates for bottom side varies from 0.646 to 0.550 mm/min, while for lateral side it varies from 0.571 to 0.517 mm/min. These rates were determined at initial moisture content of 10 and 20%, respectively.
COBISS.SI-ID: 8640609
The paper presents a new, two-phase method to determine the thermo-chemical decomposition of timber member exposed to fire. In the first phase, based on the thermal analysis, the distribution of temperatures in the characteristic cross-section of timber member is computed. Based on the pyrolysis reaction, the decomposition of wood is determined in the second phase, where Broido-Shafizadeh model is used. The main purpose and advantage of the new developed method is to determine charring of wood, charring depth and char front temperature for a timber member exposed to random fire load. Thus, the studies given in the paper present the analyses for timber member exposed to standard and parametric fire curves. The studies reveal that fire growth rate has a significant impact on the development of charring depth as well as char front temperature.
COBISS.SI-ID: 8675937