Study On New Large-Span Shaped Steel-Concrete Composite Hollow Floor

The cast -in-situ reinforced concrete hollow floor suited to large-span buildings has been put into engineering practices largely because of its architectural benefits for light weight, flat floor ceiling , as well as good behavior on heat preservation and sound insulation. Meanwhile,steel reinforced concrete (SRC) flat beam , despite of lower structural height, has great bearing capacity, high stiffness and good working ductility . On the basis of making full use of the merits of two type floor forms mentioned above, this paper ,by the method of integration of these two forms , hereby presents one new type of large-span steel-concrete composite hollow floor system.The paper discusses the conformation characteristics and requirements for two-way steel-concrete composite hollow floor.Then based on virtual work principle, by means of 3D-FEM,the shaped steel's strengthening effect on the elastic stiffness of such floor is investigated and the simplified elastic stiffness calculation formula is derived .It hence is possible to analyze the floor in light of the elastic thin plate theory. Meanwhile,a rational finite element model of one simple-supported floor under vertical uniform load is built,and by using nonlinear 3D-FEM, the analysis about its structural behavior at the elastic-plastic stage after concrete cracking is made in detail. By adopting the calculation method of SRC(steel reinforced concrete) beams,the bending moment of per unit width floor can be worked out. The paper ,hereby, discusses how to obtain the ultimate load by applying the yield line theory.For the purpose of deflection calculation based on Chinese design code, a slab strip of one grid width is taken out from the floor as a whole and the rule of its short-term stiffness variation is studied by using nonlinear 3D-FEM.On the basis of load-deflection relationship discussion and parameters anlysis,the simplified formula aimed to the calculation of the simple-supported floor slab under vertical uniform load is derived.The results indicate that this kind of floor slab can effectively provide the bearing capacity and rigidity when applied to buildings with large column span and bay width.The theoretically feasible analysis on the structural behavior of such floor system as well as discussion on design and calculation are helpful for its further study and engineering application.