Experimental Study On Bending Behavior And Design Methods Of Prestressed Concrete Composite Beams

Composite beam is familiar in the construction engineering. Compared with cast-in-place beam, it subsists of some advantages such as convenient construction, economizing molding board, shortening time limit for a project, reducing costs. Compared with precast assembly beam, it subsists of some advantages such as good integrity behavior and seismic behavior. But composite beam also subsists of some disadvantages. For example, its composite section is usually designed to plane, and the deadweight of its precast components is little large. These disadvantages influence its application. So we designed two new kinds of composite beams—with U-shaped prestressed precast beam or invertible T-shaped prestressed precast beam, and them subsist of the following characteristics: 1) the deadweight of precast beam is lightened, which will be transported and assembled expediently; 2) its lengthways reinforcing bars include non-prestressed bars, which can meliorate distribution of cracks and increase bearing capacity tractility of composite beam; 3) non-prestressed bars are placed on top of composite section, which is propitious to design and manufacturing of precast beams; 4) the area of composite section is augmented.In order to well and truly find out the bending behavior and destroy properties of composite beam with U-shaped prestressed precast beam or invertible T-shaped prestressed precast beam, experimental study have been carried through.At first, based on familiarity and analysis of the research fruit of composite beams, three composite beams with U-shaped prestressed precast beam, three composite beams with invertible T-shaped prestressed precast beam and one integral casting beam which have the same size and steel bar as composite beams are designed and manufactured. By experimenting upon these beams, their normal section craze load, bearing capacity load and flexibility are measured, and their crack development and destroy properties are observed.Afterward, based on analysis and study of normal section bearing capacity, crack resistance, crack width, flexibility and composite section shear strength of two kinds of composite beams, corresponding design methods are put forward.At last, combined with engineering practice, economical benefits, social benefits and environmental benefits of application of composite constructer system are analyzed and explained. And the working procedures and technologic characteristics are simply introduced.