Analysis Method On Stress Increment Of External Prestressing Concrete Beam Based On Deflection

Compared with traditional prestressing, external prestressing system has its own merits. That is why this kind of structure has been widely used and constantly innovated all over the world in recent years. But, As far As existing information is concerned, the study and application of this new technique are almost limited in existing structural's strengthening, mechanical behavior studies of new concrete structural with external prestressing still lack very much. Based on the analysis of a large number of pilot studies at home and abroad research data, specifications, as well as the basis of ralated literature, through the five simply supported beam and four two-span continuous beam test, more systematic analysis of stress increment and deflection deformation of the principle and method of caculation, specific research work are as follows:On the in vitro development of prestressed concrete structures and research, comprehensive analysis of externally prestressed structures at the ultimate bearing capacity under a wide variety of computing theory, and discussed their respective advantages and disadvantages.At loads lower body external tendons of beam displacement and nothing to do with the stress in vitro tendon force can change the entire root beam deformation conditions are. Through the incremental stress and deflection analysis of the inherent law changes, derived from a different cloth reinforcement forms, under different loading mode changes based on the deflection formula for calculating the stress increment, the formula applies to simply supportes beams and statically indeterminate beams.Specimens of 9 external prestressing concrete beams, including 5 simply-supported beams and 4 two-span continuous beams , and the static load tests were finished. Several critical dates as deformations,strains of the beams and the stress increments of external tendons were measured, and the test results were analyzed. Analysis of test results found that in vitro ten don force and the stress increment in the deflection of beam cross-linear or approximate linear relationship.After comparing calculated values with experimental values of stress incremeng of exermally prestressed tendons. based on the deflection formula for calculating the stress increment by this formula is almost as accurate as the result of the test.