Scale modeling of thermo-structural fire tests

Standard methods for fire resistance testing require large-scale assemblies and are typically conducted on specialized furnaces at considerable cost. This research focused on developing a scaling methodology for a reduced-scale fire resistance test that reduces the size of the test article while maintaining the same thermal and structural response exhibited in the large-scale test. The developed scaling methodology incorporates uniform geometric scaling, Fourier number time scaling, and furnace boundary condition matching. The scaling laws were experimentally validated with fire exposure tests on gypsum wallboard samples at three scales (full-scale, 1/2-scale, and 1/6-scale). In the tests, samples were exposed to a full-scale equivalent of 60-min of ASTM E119 fire curve exposure on a reduced-scale horizontal furnace, and the temperature rise through the thickness profile was measured. Models were created to calculate the modified fire curves for the smaller-scale tests. Experimental results show that on the exposed surface, the 1/2-scale absolute temperature was within 1.7% of full-scale, while the 1/6-scale temperature was within 2.5%. While the time-dependent properties of burning and cracking caused visual differences in these gypsum tests, modeling and temperature measurements demonstrated that the test results were thermally similar. The good similarity of temperatures is achievable in fire exposure tests of non-combustible gypsum wallboard down to 1/6-scale.