Structural modelling of light-timber framed walls in fire

Described in this paper is a structural response model, FIREFRAME, for determining deflections, stresses and times to failure of gypsum board clad light-timber framed walls exposed to realistic fires. The model was developed for use in accordance with performance-based building fire regulations. To determine dominant phenomena to be modelled, experimental observations were undertaken. These phenomena, although complex, are simply modelled with common frame analysis methods. The validity of the model was checked numerically and experimentally. The model is fast, robust and numerically accurate giving predictions within 2.0% of solutions obtained with closed-form and finite element methods. Good comparisons are demonstrated between experimental measurements and model predictions for fire-exposed walls in common building construction. The failure time of slender walls, however, was overestimated with the model. Improvements to modelling creep in wood in compression at approximately 100°C are required. From modelling results it is apparent that gypsum board and studs can be modelled as fully composite, provided strength and stiffness of gypsum board is assumed to reduce quickly to zero as temperatures in the board rises above 100°C.