Study Of Load-bearing Properties Of Prestressed Concrete Hollow-casted Slab-beam System

Prestressed concrete hollow-casted floorslab is a new kind of structure system, it has the virtue of light weight, hard stiffness and so on. With the development of construction technic, the structure system is widely used in construction building now. However, its detailed mechanical properties is not studied. The most important to structure engineers is that whether the design theory in the RC structure codes is appropriate. This paper emphasizes particularly on the studies of the effective width of flange and bidirectional load distribution, relative to the structural design.In the dissertation, a full-scaled experimental study is firstly conducted, according to an actual engineering with application of prestressed concrete hollow-casted floorslab. There are two load cases are studied respectively, one is vertically uniform load, and the other is axially prestress load. The strain distribution of flange of girder, both in support position and in mid-span position, is studied. The effective width of flange is also calculated.In the dissertation, according to the ratio of moments in mid-span of girder, the formulas to calculating load distribution are achieved. Based on these formulas and the experimental results, the deliver rule of the vertically uniform load on the floorslab is indicated. According to comparison results of with or without prestressing force, the influence to load deliver rule by prestressing force, is also studied. The experimental results also indicate biaxial bending of concrete hollow-casted floorslab.To understand the mechanical properties of this new structure system better, a finite element method is introduced. Using the finite element program-ANSYS, a three-dimensional solid finite element model is constructed, with which the strain and stress distributions along the flange of girder, both in support and mid-span position, are numerical studied. The deliver rule of the load is also studied, according the finite element calculating.Because calculating with a three-dimensional solid finite element mode, consumes much time and calculating resource, it is not appropriate to study the influence of structure parameters on the load deliver rule. In case of that deformation, internal force and structural stiffness of calculating model should approximate to original structure, Two simplified model called the lattice beam FEA model and orthotropic plate FEA model respectively, are established to simulate original structure. The comparison of calculating results between two simplified are compared with 3D solid model, indicate that the orthotropic plate model is more accurate. With the orthotropic plate model, the influence of structure parameters, including of floorslab's ratio of length to width, rigidity ratio of main girder in two directions and rigidity ratio of hollow cast floorslab in two directions, on the deliver rule of vertical load on the floorslab, is approached, and some regressive formula and graphs, which can be referred in actual engineering and structural design, are achieved.