Computational Simulation of Timber Charring in an Approach across Scale

Presented by Franz Richter, PhD Student, Imperial College UK

Cross Laminated Timber (CLT) is an emerging and promising construction material for high-rise buildings. It is strong, sustainable, and cost-efficient. Around the world, skyscrapers out of timber up to 300 meters are proposed by architects. Many regulators, fire fighters, and residents are concerned by these heights, because of the perceived low resistance of timber to fire. This perception stems from your limited understanding of its fire behaviour. For example, in structural applications the charring rate of timber can be used to determine the loadbearing capacity. Based on furnace tests following the standard fire curve, the charring rate is assumed to be one constant valid under all conditions. Charring, however, is a complex interplay of heat transfer and chemistry. It depends on the fire. The simplification of one universal charring rate is a serious limitation to engineering and performance-based design. A general model for the charring of timber under standard and realistic fire conditions is needed. In this webinar, we will present the physical fundamentals of charring together with our work towards developing such a model. Fundamentally, charring is controlled by chemistry as well as heat and mass transfer. We found that the common assumption of neglecting the chemistry is erroneous, and developed, at the microscale (mg-samples), a kinetic model for the chemistry of charring. At the mesoscale (kg-samples), we combined this kinetic model with a heat and mass transfer model. The resultant model is able to predict charring rates under different fire conditions—different heat fluxes and oxygen concentrations. Scaling the model to the macroscale (buildings) offers the potential to predict charring rates under realistic fires. At each scale, however, significant work remains, both experimental and modelling-wise, to better understand the fire behaviour of timber and achieve predictions of the same accuracy as for steel and concrete structures.

SFPE MEMBER FEE: FREE

NON-MEMBERS FEE: $29