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Thermal Performance of Fire Resistive Materials III. Fire Test on a Bare Steel Column.


pdf icon Thermal Performance of Fire Resistive Materials III. Fire Test on a Bare Steel Column. (592 K)
Bentz, D. P.; Hanssen, L. M.; Wilthan, B.

NISTIR 7576; 83 p. April 2009.

Keywords:

steel columns; fire resistant materials; fire tests; time; temperature; thermocouples; thermometers; methodology; high temperature; ASTM E119; heat transfer; emissivity; exposure; standards

Abstract:

This report is part III in an ongoing series concerning the characterization and modeling of the thermal performance of fire resistive materials (FRMs). In part 1, a methodology for characterizing FRMs to provide quantitative material property inputs for thermal performance models was outlined, and in part 2, one such multi-layer model was demonstrated for simulating the results of high temperature slug calorimeter experiments conducted in a small furnace. Attempts to extend the one-dimensional model to predict the performance of FRM-insulated steel columns in a standard ASTM International E119 fire exposure were successful only when a safety (viewing) factor of approximately 0.5 was introduced for reducing the radiative heat transfer between the fire and the protected column. To justify this fitted value of the viewing factor, a simpler fire test of a single bare W14x233 structural steel column was conducted in the column furnace at a commercial U.S.-based testing laboratory. This report presents the results of that test, along with an analysis based on a previously developed general heat balance equation. The emissivity value that provides the best fit to the experimental data is contrasted against the measured emissivity of the structural steel. The resultant safety factor is found to be on the order of 0.45, in general agreement with the value used previously in the one dimensional thermal model. One unique feature of this study is that data was also collected during the (slow) cool down period that followed the termination of the fire exposure, allowing a comparison of the convective heat transfer coefficients during a fire exposure and subsequent cooling in a furnace environment. Additional thermocouples were placed on the steel column and the furnace walls and two plate thermometers were placed near the surface of the steel column to better characterize the furnace fire environment. All of the measured data is provided in an Appendix to place it in the public domain where it may serve as a reference data set for other researchers.