Experimental fire tests were conducted on four 12.8 m long steel-concrete composite floor beam assemblies with varying end support conditions, including two types of simple shear connections (shear tabs or welded-bolted double angles) and slab end continuity. Each specimen was constructed as a partially-composite beam, consisting of a lightweight concrete slab on formed metal decking supported by a W18x35 steel beam acting compositely via 19 mm diameter headed stud anchors spaced 305 mm. While resisting an ASCE 7-specified gravity load using hydraulic actuators, each specimen was exposed to a structurally significant fire that was produced using three natural gas-fueled burners distributed on the floor of the test compartment with the maximum heat release rate of 4 MW. Imposed mechanical loading and fire characteristics, thermal and structural responses, and structural failure modes of the specimens were studied.