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The policy of the National Institute of Standards and Technology is to use metric units in all its published materials. Because this report is intended for the U.S. building construction industry, which uses inch-pound units, it is more practical and less confusing to use inch-pound units, in some cases, rather than metric units. However, in most cases, units are presented in both metric and the inch-pound system. Certain commercial entities, equipment, products, or materials are identified in this document in order to describe a procedure or concept adequately. Such identification is not intended to imply recommendation or endorsement by the National Institute of Standards and Technology, nor is it intended to imply that the entities, products, materials, or equipment are necessarily the best available for the purpose. Another policy of the National Institute of Standards and Technology is to include statements of uncertainty with all NIST measurements. In this document, however, some measurements of authors outside of NIST are presented, for which uncertainties were not reported and are unknown.

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A series of compartment fire experiments was conducted on long-span steel-concrete composite floor beams designed and constructed following U.S. building codes and standards. The test program consisted of five 12.8 m long composite floor beam specimens with various end support conditions. Each specimen was constructed as a partially-composite beam consisting of a W18×35 steel beam and an 83 mm thick lightweight concrete slab cast on top of 76 mm deep ribbed steel decking units. Test variables included two types of simple shear connections (shear-tab and welded/bolted double-angle connections) and the slab continuity over girders. One specimen with the double-angle connections at the ends was tested at ambient temperature and the remaining four specimens were tested under simultaneous mechanical and fire loading. This report, Part 1, presents details of the test setup, specimens, design basis of fire loading, instrumentation, and the behavior of the composite beam with double-angle connections at ambient temperature. The ambient temperature test indicated that the composite beam specimen failed by a shear stud near the west end, followed by concrete breakout failure and yielding of the steel beam. The measured moment capacity was approximately 80% of the calculated flexural strength. The double-angle connection at the west end failed by weld fracture, which caused collapse of the composite beam. The ambient behavior of the composite beam specimen presented herein will serve as a baseline to compare with the composite beam assemblies tested under combined mechanical loads and fire exposure, which are presented in a subsequent report; Part 2 (Choe et al. 2019). The datasets obtained from these tests provide technical information to advance performance-based design of composite floor assemblies in steel-framed buildings subject to fire.