Load-resisting mechanisms of 3D composite floor systems under internal column-removal scenario

To elucidate the load-resisting mechanisms of three-dimensional steel-frame-composite-floor systems (3D composite floor systems) under internal column removal scenario, such as tensile membrane action and catenary action, a large-scale experimental test was conducted. A two-by-two bay specimen was tested quasi-statically to failure by using a special loading and restraint system. The test specimen was scaled down from a prototype structure to a 1/3 model due to laboratory space constraint. Based on this test, the load-deflection response of the 3D composite floor subjected to internal column loss is obtained. Besides, the peak load-carrying and deformation capacities are obtained and the failure modes are discussed in detail. Stress states and deformation of the floor components including steel beams and decking are also presented. To gain deeper insight into the load-resisting mechanisms, the respective contributions of individual floor system components are separated, which include the double-span girder, double-span secondary beam and composite slabs. Finally, the vertical load redistribution among surrounding columns is evaluated to find the load transfer path at large deformation stage.