Study Of The Properties Of Precracked-Prestressed Reinforcement Concrete Beam Under Ultimate Prestressed Loading Condition

Based on the understanding of the cracks in reinforced concrete beams, from the fracture mechanics, the group proposed an approach which based on the ideology of crack-control and developed a precracked-prestressed high-strength reinforced concrete beams. The early stage of some experiments that group carried out about precracked-prestressed high-strength reinforced concrete beams were under the conditions of application of load-carrying capacity of 30%, 50% and 70% of the ultimate loading. Some conclusions that precracked-prestressed reinforced concrete beams have excellent mechanical properties are obtained. If precracked-prestressed reinforced concrete beams would be produced under the conditions of application of the beams' ultimate load-carrying capacity, one can design a larger pre-camber for precracked-prestressed reinforced concrete beams, and then chose a design load as control load, then can produce of precracked-prestressed reinforced concrete beams with different prestress degree.In order to verify the feasibility of precracked-prestressed reinforced concrete beams under prestressed loading at the condition of ultimate load-carrying capacity, experimental study have been done and some mechanical properties of the beam are carried out as follows:The beam have obtained effective prestress: in the whole loading process under the ultimate prestressed load the obtained precracked-prestressed beam have better laws of linear elasticity without any crack. After over the ultimate load, the beam cracks and its stiffness continue to decline but can get an stability upper the ultimate loading. The beam have a stronger effect of anti-cracking and crack-resistance. When reloading the beam's stiffness remains high under the ultimate load-carrying capacity. Compared with an ordinary high-strength reinforced concrete beam, load-carrying capacity which controlled by deflection control index of precracked-prestressed reinforced concrete beams are significantly improved.