Membrane Action of Composite Fibre Concrete Slab in Fire

Abstract

The fire resistance of a properly designed floor structure increases by its membrane behaviour. The membrane fire resistance is evaluated by advanced as well as simple design procedures, approved by tests, and for partially protected floors reaching 60 mins and more. Composite constructions are more and more reinforced by steel fibres without added steel bars. Due to distributed mesh, steel fibre concrete can achieve good deformation capacity compared to traditional reinforced concrete even at elevated temperatures and questions have been raised about its fire resistance. The composite floor slabs with fibre concrete at ambient and at elevated temperature were tested at the Czech Technical University in Prague in the last two years. At elevated temperature, the floor was only partially fire protected. Intermediate beams and fibre-concrete slab in steel sheeting were without protection. Concrete slabs were reinforced by steel fibre only without added steel bars. The main aim of the tests was to demonstrate the suitable properties of the steel fibre concrete slab in fire. For the fire resistance of the floor slabs it is important that the material has sufficient ductility and adequate tensile and shear strength. These material properties of the fibre-concrete allow the slab to create a different load bearing mechanism, which increases the fire resistance of the floor slabs. The fibre-concrete was tested at ambient and at elevated temperature with a focus on ductility and tensile strength of the fibre-concrete.