Structural Timber In Compartment Fires – The Timber Charring and Heat Storage Model

The influence of exposed timber surfaces on compartment fires has been well documented in various studies in recent decades. Yet available design concepts still typically neglect the influence of an additional fire load from linear structural timber elements such as beams and columns. As rules for large shares of exposed timber surfaces, e.g. by panels, are rare, authorities and fire safety engineers demand often mock-up compartment fire experiments to estimate the fire safety of a particular design. Such experiments, however, are costly, time consuming, and give limited insights into the potential fire scenarios and may fail to represent properly the fundamental effects arising from exposed structural timber elements in a fire. An approach to overcome these existing limitations is presented, which is able to estimate the contributions from structural timber to a fire from its fully developed- and decay phase until burnout. The model input is developed from an experimental campaign where the relevant effects of fire exposed structural timber could be isolated and measured. It was found that the energy stored in the char layer is a key characteristic for describing the fire dynamics of compartment fires with exposed structural timber. Consequently, the proposed approach describes a framework for the Timber Charring and Heat storage, the TiCHS-model. The validation of the model is shown in this paper by means of existing compartment experiments. A current limitation is the bond line integrity of the fire exposed components as the combustion characteristics of failed char pieces on the floor are currently unknown.