An Integrated Model to Predict Fire Resistance of Wood Floor Assemblies

Abstract

An integrated numerical model to predict the fire resistance of wood-framed floor assemblies has been developed. The assemblies considered in this article are floors constructed with nominal 2 × 8 (38 × 191 mm2), 2 × 10 (38 × 241 mm2) or 2 × 12 (38 × 292 mm2) wood joists lined with Type X gypsum board (12.7 mm or 15.9 mm thickness) as a ceiling membrane with (or without) resilient channels and 15.9 mm thick plywood as a sub-floor. The model includes a heat transfer sub-model to calculate the flow of heat in the assembly and a structural sub-model to evaluate the mechanical performance of the assembly. The heat transfer sub-model employs two-dimensional heat conduction equations to predict the temperatures in the ceiling (gypsum board), wood joists and sub-floor of the assembly when the ceiling is exposed to fire. Using the temperature distribution in the joists predicted from the heat transfer equations, the structural sub-model analyzes the mechanical strength of the joists and calculates joist deflection in the assembly. Results from the numerical model are compared to results from full-scale tests. Reasonably good agreement is observed.