Three-Dimensional Composite Floor Systems under Column-Removal Scenarios

Abstract

In this study, four 1/3-scaled enhanced steel frame–composite floor specimens were tested quasi-statically under a column-removal scenario. One specimen was the control test and the other three were different in terms of aspect ratio, degree of composite action, and boundary condition. The objective of this paper is to study the effects of these three parameters through comparing experimental results of the four specimens. The comparisons revealed the effects on load-carrying capacity, ductility, failure mode, deformation characteristics, and load redistribution among the remaining columns and reaction forces from surrounding structures. First, the load-carrying capacity of the specimen with slab panel dimensions of 2×2 m was around twice as great as those of specimens with slab panel dimensions of 2×3 m, while the deformation capacity of the former was much smaller than those of the latter. Second, weaker composite action decreased flexural resistance but improved ductility significantly, which was beneficial for development of tensile membrane action. Third, more flexible boundary conditions could not increase applied load beyond the stage dominated by flexure. For composite floor systems, flexural rigidity of steel columns was sufficient to support development of compressive arch action (CAA) so that additional horizontal restraints from surrounding structural members were not so beneficial at the CAA stage. However, the stiffness of additional restraints significantly affected the floor system at the catenary action stage. Finally, the typical yield pattern of composite slabs comprised negative yield lines that were formed around the perimeters and positive yield lines along the double-span girder, the double-span beam, and the paths connecting corner columns to the nearest loading points.