Defining Design Fires for Structural Performance

This paper presents a pilot study that was performed to develop design fires for an office compartment and to use these fires to analyze structural performance at elevated temperatures. Published information on office planning was used to define three model layouts and their furnishings. The CFAST computer program was used for parametric modeling of the fire conditions within each of the three layouts, subject to the following variables: ventilation, surface materials, heat release rates, and ceiling heights. The heat release rates were based on test data compiled and published by researchers at the National Institute of Standards and Technology (NIST). The results obtained from the fire models indicated that flashover occurred in a limited number of scenarios. The time temperature curves obtained for these flashover conditions were then used for combined thermal and structural analyses of both exposed and insulated steel beams. The ASTM E-119 standard time-temperature curve was also used for thermal and structural analyses as a benchmark. In addition to presenting the results of the study, the paper concludes with recommendations and proposals for future work.