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Experimental Study on Fire Resistance of a Full-Scale Composite Floor Assembly in a Two-Story Steel Framed Building



Lisa Choe, Selvarajah Ramesh, Xu Dai, Matthew Hoehler, Matthew Bundy


The purpose of this paper is to report the first of four planned fire experiments on the 9.1 m × 6.1 m steel composite floor assembly as part of the two-story steel framed building constructed at the National Fire Research Laboratory. This paper presents the fire experiment that was aimed to quantify the fire resistance and behavior of steel-concrete composite floor systems commonly built in the United States. The test floor assembly, designed and constructed for the 2-hour fire resistance rating, was tested to failure under a natural gas fueled compartment fire and simultaneously applied mechanical loads. This experiment showed that the protected gravity beams and girders of the test assembly achieved matching or superior fire resistance based on the acceptance criteria of standard furnace testing. However, the composite slab exhibited a potential fire hazard associated with the use of a minimum code-specified shrinkage reinforcement (60 mm2/m) within the specified fire rating period. The heated slab cracked around the internal edges of the test bay less than 30 min into heating, followed by center cracks along the secondary beam at 70 min. This center breach was accompanied by ruptures of wire reinforcement in tension, i.e., due to catenary action along the shorter span of the test floor assembly. This result suggests that the code-specified minimum steel reinforcement in the slab prescribed for normal conditions may not be sufficient to activate tensile membrane action under the 2-hour standard fire exposure. This work was the first-of-kind fire experiment conducted in the United States to study the full system-level structural performance of the composite floor assembly subjected to the compartment fire using natural gas as fuel to mimic a standard fire environment.
Journal of Structural Fire Engineering


Composite floor, Steel structure, Fire resistance, Compartment fire


Choe, L. , Ramesh, S. , Dai, X. , Hoehler, M. and Bundy, M. (2021), Experimental Study on Fire Resistance of a Full-Scale Composite Floor Assembly in a Two-Story Steel Framed Building, Journal of Structural Fire Engineering, [online],, (Accessed April 15, 2024)
Created October 7, 2021, Updated November 29, 2022