LOAD-CARRYING CAPACITY OF COMPOSITES SLABS WITH STEEL-STUDS IN ISO-FIRE

To examine properties and load-carrying capacity of composites slabs of steel plates with steel studs and concrete with top reinforcements in ISO fire, fire tests and analyses of heat transfer and elasto-plastic stress-deformation were carried out. And a simple calculation method to evaluate load-carrying capacity of composites slabs was proposed. This calculation method based on simple plastic theory on the viewpoint of considering in strength degradation zone of concrete by heat transfer during fire. After this study, the following conclusion could be obtained. 1) The composites slabs designed within the limit of ordinary live load have flexural failure mode in fire and the load-carrying capacity of composite slabs can be calculated by using the formula proposed. 2) Composite slabs with steel studs having shear stress more than 0.5N/mm^2 collapse by shear stress on the initial stage of ISO fire. This shear failure is caused by decreasing of shear strength of concrete due to giving rise to tensile stress in concrete. Tensile stress in concrete increase on the initial stage of fire, because of the restraint of elongation of steel plates through steel studs. 3) However, generally, composite slabs have axial restraint more than 30% of full axial restraint in structure, the decreasing of shear strength of concrete doesn't occurred during fire, so shear failure can be avoided.