Research On Static And Dynamic Behaviors Of Concrete Bridge Reinforced By Prestressed External Tendons

As a branch of the post-tensioned prestressing system, external prestressing technique has become a hotspot of prestressing techniques in recent years. External prestressing means that the prestressing bars are disposed outside the beam bodies, which in tradition are inside the beams with or without bond. At present, external prestressing technique is used on prestressed concrete bridges, large-span space structures and strengthening of existing old concrete bridges and other structures, which is an important aspect of its applications. At home, research on the external prestressing technique is not much, and studies on mechanical performances of this kind of structure system is quite limit, meanwhile engineering practices are few, and the corrresponding specifications and codes for design and construction are lacking, all of which lead to advantages of the system are not sufficiently exhibited. Nowdays, external prestressing technique is used worldwidely and is developed continually. It is urgently necessary to probe into theoretics and practice actively, to deduce applicable design methods, accordingly to promote the application and development of external prestressing structures.An important step in structure design is the calculation of the ultimate flexural strength of external prestressed concrete beams, which needs to calculate the ultimate stress increment of external tendons first. The study in the paper starts with beam distortions, and it treats the plastic deformation area as pure bending sect, rest of the beam as rigid bodies. According to different shapes of the external tendons, it divides into three structural forms familiar in projects, that is the beams with no deviator, with a deviator and with two deviators, and studies the relation between the deformation of the external prestressing tendons and that of the beams, and derives the formulas of the ultimate stress increment of external tendons. In the formulas, the ultimate angle corresponding to half of the plastic deformation area is considered as a variable parameter. Furtherly bearing capability of the beams is easy to calculate. Results obtained from this method is compared with results from regulations for prestress concrete structure without bond and other methods suggested in other documentations. It shows that the method suggested in the paper is simple, applicable for engineering and has good precision.On the bases of the formulas deduced, and combining with relative test datas, it studies in the paper several factors influencing the bearing performance of the simple beams, such as shape of the external tendons, the equal moment segment length, span-to-depth ratio of the beam, valid initial prestress of the external tendons, area of the internal tension reinforcement, strength of the concrete, vertical distance between...