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The purpose of this paper is to report the first of four planned fire experiments on the 9.1 × 6.1 m steel composite floor assembly as part of the two-story steel framed building constructed at the National Fire Research Laboratory.

The fire experiment was aimed to quantify the fire resistance and behavior of full-scale steel–concrete composite floor systems commonly built in the USA. The test floor assembly, designed and constructed for the 2-h fire resistance rating, was tested to failure under a natural gas fueled compartment fire and simultaneously applied mechanical loads.

Although the protected steel beams and girders achieved matching or superior performance compared to the prescribed limits of temperatures and displacements used in standard fire testing, the composite slab developed a central breach approximately at a half of the specified rating period. A minimum area of the shrinkage reinforcement (60 mm²/m) currently permitted in the US construction practice may be insufficient to maintain structural integrity of a full-scale composite floor system under the 2-h standard fire exposure.

This work was the first-of-kind fire experiment conducted in the USA to study the full system-level structural performance of a composite floor system subjected to compartment fire using natural gas as fuel to mimic a standard fire environment.