Resarch On The Static Test Performance Of The Bi-Prestressed Concrete Beam

The bi-prestressed concrete is a compound prestressed concrete, we could make whose compressive area bear pretension and tensile area bear compressive stress. By using this system, the weak tension capability of concrete was overcome and the behaviors of the concrete will improve a lot .Theoretically, this could make the concrete structure reach a so called"zero stress"state and enhance the bending strength greatly .For decreasing the size of section and the beam's deadweight , the bi-prestressed concrete will have a board future in bridge construction. The research on this system of this paper is mainly in the following aspects.1. Through the analysis of the stability of the steel tube and the research on the construction technology of the beam, We could summarize the main points that play a good role in construction.2. Through the test of four bi-prestressed beams , the efficiency of system, which is made of prestressed steel tube and pretensioned steel bar, is investigated .By analyzing the beam's invert arch value and the stress losses of the steel tube in the process of applying the prestress, we could draw a conclusion that the pre-compressive steel bar could offer a effective prestress.3. The items in the test of the bending capacity of four beams include the deflection in the middle of beams ,the angles of rotation at the support of beams, the strain of the beam section and the accordant deformation between steel tube and concrete.4. The analysis of the prestressed concrete with the help of finite element method software ANSYS.The study of the test shows that comparing to the common prestressed concrete , the bearing capacity of the bi-prestressed concrete has improved a lot; deformation properties of the concrete in elastic stage and after cracking varies greatly in different levels. The higher levels, the better bearing capacity. Under unloading conditions, the concrete crack has retracted a lot and the deflection of the middle beam has get much smaller. Besides, the anchorage performance between steel tube and concrete is still well when the beam get seriously damaged.