Fire Resistance Test of Concrete Composite Box Steel Girder Floor System

Abstract

The concrete composite box steel girder floor system is a new box-section ribbed hollow floor system. It is an integral structure integrated the girder and plates by the “composite box”, one of the precast composite members and the rear casting ribbed girder and has been widely used in the buildings with large span and heavy load. The article researches its whole process under the effects of the fire and the service load. In the whole process of test, the temperature field, vertical displacement, displacement within the plane, plate edge corner and other parameters of the different sections have been measured. The results show that: the concrete at the bottom plate of the composite box bottom plate quickly bursts off during the fire; later, the bottom plate of the composite box is out of operation; the floor structure becomes cross girder structure; as the temperature rises, after the floor system structure becomes the cross girder structure, the torque of the four-side ribbed girder of the floor system increases and the diagonal cracks occur on the four-side ribbed girder; as the temperature rises, there is large temperature gradient on the floor system ribbed girder along with the cross section height; the flexural deformation occurs to the floor system while the expanding deflection occurs in the plane; the maximum vertical displacement is achieved after the temperature rise stops; along with the drop of the temperature, the flexural deformation gradually recovers; after the tested temperature rise has been conducted for 292 minutes, the floor system still has good fire resistant capacity