Structural modelling of light-timber framed walls in fire

Described in this paper is a structural response model, FIREFRAME, for dete rmining deflections, stresses and times to failure of gypsum board dad ligh t-timber framed walls exposed to realistic fires. The model was developed f or use in accordance with performance-based building fire regulations. To d etermine dominant phenomena to be modelled, experimental observations were undertaken. These phenomena, although complex, are simply modelled with com mon frame analysis methods. The validity of the model was checked numerical ly and experimentally. The model is fast, robust and numerically accurate g iving predictions within 2.0% of solutions obtained with closed-form and fi nite element methods. Good comparisons are demonstrated between experimenta l measurements and model predictions for lire-exposed walls in common build ing construction. The failure time of slender walls, however, was overestim ated with the model. Improvements to modelling creep in wood in compression at approximately 100 degreesC are required. From modelling results it is a pparent that gypsum board and studs can be modelled as fully composite, pro vided strength and stiffness of gypsum board is assumed to reduce quickly t o zero as temperatures in the board rises above 100 degreesC. (C) 2001 Else vier Science Ltd. All rights reserved.