Research On Bending Performance And Ultimate Load Of Externally Prestressed Concrete Simple Supported Beams

In recent years, many domestic and international bridge scholars has done lots of tests and theory analyses, in order to study the bending behavior of externally prestressed concrete structures, but the result one presents is discrepancy with another, so the question needs a further study. This paper studies mainly according to the simple supported externally prestressed beams.(1) To the shortcomings of exist methods, bases on fact that the total length of slipping cables without stress remains constant and structure warps to coordinate, this paper presents a method to analysis the force and the deflection of the structure . Moreover, this method considers both the relative slip between the deviators and the external tendons and the difference between the static friction coefficient and the sliding one. The method is more popular and more precise than method mentioned in the article.(2) This paper has elaborated the step and the principle of Cranstan iteration method to calculate the rigidity of plane beam element when the material nonlinearity is considered. Because Cranstan iteration method does not show restraint sometimes after the reinforcing bars yield, the paper put forward an efficiently improve measure to solve the question.(3) A general FE model, which can analyse reinforced concrete structures and externally prestressed concrete structures up to failure is presented. The model takes into account material nonlinearity and geometric nonlinearity. Based on the general FE model, a nonlinear FE program was developed. A large-scale model test is analyzed in order to verify the general FE model and the program.(4) The paper implements a study about some factors having influences on the bending behavior of externally prestressed concrete simple supported bridges .these factors include the change of PPR, the change of match tendon rate, the change of static friction coefficient and the sliding one, the reasonably scope of these parameters value is given.(5) Basing on the research of other scholars and analysis of this paper, the author gives some useful suggestion on the design of externally prestressed structures.