Research On Mechanical Characteristics And Analytical Method Of Thin-wall Core Box Cast-in-site Hollow Floor

Cast-in-site Hollow Concrete Floor System is one of the newest types of floor system occurred in China. This kind of floor system have many advantages such as stinting material, lightening deadweight, larger span, better effect in insulation of thermal and sound, and it can greatly knock down the synthetic cost. Though Technical specification for cast-in-situ concrete hollow floor structure was issued and implemented, there still exist many questions. For example, the design methods of hollow-concrete-floor-system projects and the classification boundaries of different type of slab are both not clear, etc. In this paper, through theoretical analysis and software calculation, the research has been done as followings.(1) Finite element models of Single piece hollow slabs, with different beam’s section, were built in this paper. Through these model results, following conclusions were drawn:1) the slab bending moments near the region of the column and the supporting beam could greatly reflect the supporting role of the beam playing to slab;2) beam-supporting-slab was defined in this paper based on the model bending moment distribution.(2) In order to investigate the mechanical behavior of the hollow floor-slab in inner panels precisely, the finite element models were applied to calculate the moment distribution of the slab under different conditions, such as the beam-slab stiffness ratio and the length-width ratio of slab, and then compared the feature moment value with the hollow slabs with four edges clamped, and conclusions were drawn as follows:1) when the length-width ratio of slab was between0.5and1, and the beam-slab stiffness ratio was greater than2, this slab could be judged as beam-supporting-slab;2) aiming at this kind of hollow slab, a simplified method of calculating the feature moment was given in this paper. (3) Having applied some new finite element models with different cast-in-site hollow slab local parameters, different length-width ratio and loads to calculate the moment distribution, it proved that the simplified method which was used to calculate the feature moment was feasible.