Charring Models for Timber

Abstract

In this thesis, charring models of timber have been inspected and three of them are chosen for comparison. Those are the Brandon’s model (FSUW book), Eurocode Model (prEN 1995-1-2:20YY + EN 1991-1-2) and Combined Model (Cumulative temperature charring model (prEN 1995-1-2:20YY) + DIN EN 1991-1-2/NA). The combined model does not exist in current codes, it is a combination of two different codes. The comparison is made by using three sets of experimental data which are from FSUW book, RISE research paper and compartment tests conducted in ETH Zurich. The first two sets are conducted on full scale compartments, the latter one conducted in small scale compartments.

The models’ predicted values for compartment temperature and char depth at the end of the fire are compared with the ones measured in the experiments. Also, a sensitivity analysis is done to see the effect of selected parameters such as combustion factor and time dependent modification factor (α). Afterwards, a new method of using two different time dependent modification factors for the combined model is created and compared with the older version which uses only one α value for entire duration of fire. The results suggest that using the updated version of combined model which has two α values gives closest predictions to the experimental measurements. However, additional analyses with different compartment tests can be useful to get more precise results. Further study on the topic of using more than two α values is suggested to be an interesting and important improvement.