Study On Spatial Action Of Steel-Concrete Composite Floor

Steel-concrete composite floors have been widely used structures for their excellent technical and economical benefits in recent years. Composite floors offer many advantages, such as reducing structural height and weight, saving materials, shortening construction time, etc. However, the development of this floor system has been restricted in many cases, such as complicated load cases and strict technical cases. So it is necessary to study the spatial action of the steel-concrete composite floor to develop its potentials. In practice, the spatial action of composite floor has been ignored in domestic codes, and as a result the design method is needed to be modified.In order to verify the spatial action of the composite floors, a 1/4 scale specimen was designed based on Beijing Sanhe Power Plant frame, then it was tested under cyclic loading to investigate the spatial actions of steel frame system, steel frame with horizontal brace system and steel frame-concrete slab system. Based on the experimental results, the spatial actions of the braces and composite floors in structures are compared. The conclusions can be drawn that the spatial action of the composite slab is obvious, so the horizontal braces are met needed in most cases and in frame design the contribution of the composite floor should be considered. The seismic performance of the semi-rigid frame has been analyzed on the basis of a semi-rigid connection model, and then the parameter analyses has been conducted. Three design methods for the semi-rigid plane frame have been proposed, i.e. finite element method, iterative method and FEA software method. A calculation method is proposed with the assumption that the spatial composite frame is simplified as a plane frame, and then the calculation results and experimental results have been compared. The limit analysis method for semi-rigid frames and a simplified method are proposed, and the behavior of the composite beams in the frame are analyzed. Experimental and theoretical researches demonstrate that the spatial action of composite floor is obvious, and as a result the horizontal braces can be replaced by floor slabs in practice. The simplified design method is suggested that when calculating the stiffness of the frame it is necessary to consider the composite action of the concrete slab, while for calculating the capacity the composite action can be ignored. In initial analysis, it is unnecessary to consider the composite behavior. The calculation results using the method developed in the thesis show good agreement between those of tests and elastic analysis, elastro-plastic analysis and ultimate analysis, so the suggestion can be referenced in practice.