A UNIFIED APPROACH FOR FIRE RESISTANCE PREDICTION OF STEEL COLUMNS AND FRAMES

For a long time, the Rankine method has been applied successfully to steel columns and frames subjected to increasing loads but maintained at constant ambient temperature. This paper extends the Rankine formula to steel columns and frames under fire conditions. The authors present a simple expression for buckling coefficient that can be used for both columns and frames under fire conditions, taking the deterioration of steel properties at elevated temperature into consideration. The Rankine predictions are compared to test results of 34 axially-loaded columns, 12 sway-frames and 6 non-sway frames. It is found that the predictions agree very well with the test results. For the 34 steel columns, the mean of agreement of ratios of collapse temperatures Ttest/TRankine is 0.98 with a coefficient of variation (COV) of 5.4%. As for the 18 steel frames, the mean is equal to 0.99 with a COV of 9.2%