Experimental evaluation of thin composite floor assemblies under fire loading

This paper presents the behavior observations, results, and findings from experimental investigations of the structural behavior of thin composite floor systems subjected to combined gravity loads and fire loading. The 3.96×4.57 m floor systems consisted of A992 steel W10×15 interior beams and W12×16 girders acting composite with a 38.1-mm-deep ribbed steel deck with 63.5mm of lightweight concrete on top. Three composite floor-assembly specimens were tested with two different shear connection types (welded-bolted shear tab and all-bolted double-angle connection), two different fire scenarios (realistic fires with standard heating and uncontrolled or controlled cooling paths), and two different fire protection scenarios (i.e., interior beams with or without fire protection). The experimental results indicate that removal of fireproofing from the interior beams causes them to heat, deflect, and fail more rapidly. The beams and girders have similar deflection-versus-temperature behaviors irrespective of the fireproofing on the interior beams. The thin lightweight composite slab used in these tests contributes significantly to the load transfer from the interior beams to the girders, but it does not seem to be able to support the interior beams once they started failing. Removing the fire protection from the interior beams of thin lightweight composite slabs such as those tested in this paper is not recommended, unless better behavior can be demonstrated through future tests that include effects of neighboring floor systems.