An Analysis of the Fire Performance of Small-Scale Canadian Heritage Hardwood and Softwood

Abstract

A common consideration in the rehabilitation of historic timber structures is addressing the concerns for fire safety. Heritage structures can have softwoods but depending on the time they were built they may also have hardwoods present. Currently, there is a lack of knowledge on the char rate of heritage hardwood and softwood. This study presents initial findings into the charring of these historic materials as they would be encountered in practice through samples taken from pre-existing aged timber structures in Canada that are greater than 100 years old. The materials were tested in a cone calorimeter following a modified ASTM 1354 procedure. Hardwood samples typically exhibited a faster charring rate than the softwoods but the charring rates converged at 1.05 mm/min when exposed to higher fluxes of 50 kW/m2. As rehabilitation and readaptation may require performance-based approaches such as structural fire modelling, a provisional framework for a numerical model using LS DYNA for historic timber members is presented. The objective is to identify future research and testing areas to develop a higher certainty model. In the a-priori model presented, results showed conservative charring rate results with charring trends seen in the experiment generally being followed.