Experimental and numerical investigation of fire resistance of G550 galvanized steel-concrete slabs

This paper investigates the increasing demand for improved fire performance of composite floor systems in high-rise buildings by constructing a new type of composite slab, which is composed of concrete and closed profiled steel deck fabricated with G550 galvanized steel. Six full-scale standard fire tests of composite slabs are conducted to understand the thermal-mechanical response of the new composite slab. The results reveal that the fire duration of all the novel composite slabs exceeds 60 min, demonstrating significantly improved fire performance comparing to a conventional slab. The failure mode for all tested composite slabs is flexural failure, with limited end slip that indicates a good preservation of composite action during fire exposure. Based on the experimental results, numerical model is established and validated through the comparison of temperature and deformation data. A series of parametric analyses are carried out numerically, where overall slab depth, deck depth, supported span and uniform loads are identified as the dominant effects on the fire resistance. The results indicate that the existing design methods specified in the current standards are not fully applicable to the newly proposed composite slab. Simplified calculating methods for insulation-based and bearing capacity-based fire resistance are suggested.