Steel-Concrete Composite Floor Systems Subject to Fire, Phase 2

A series of large compartment fire tests was performed to investigate the behavior and fire-induced failure mechanisms of full-scale composite floor assemblies with a two-story steel gravity frame, two bays by three bays in plan. A total of three 9.1 m × 6.1 m composite floor specimens with varying slab reinforcement and fire protection schemes for the secondary beam were tested under combined mechanical loads and compartment fire exposure. The first experiment (Test #1) was designed to achieve a 2-hour fire resistance rating per current U.S. practice and create baseline data for the behavior of the building. Test #1 specimen had the minimum specified reinforcement permitted in the U.S. for the composite slabs with profiled steel decks. Test #2 was conducted to study the effect of enhanced slab reinforcement with larger area and ductility on the fire resilience of the composite floor systems. Test #3 was conducted to study the effect of enhanced slab reinforcement as well as unprotected secondary beams on the fire resilience of the composite floor systems. Similar to Test #2, the floor slab in the test bay was reinforced with 9.5 mm diameter deformed bars with a center-to-center spacing of 30 cm. Unlike in Test #1 and Test #2, the secondary beam and its end connections in the test bay were left unprotected in Test #3.