Prestressed With Localized Tendons Reinforced Concrete Statically Indeterminate Structure Internal Force Analysis

Prestressing can effectively improve the cracking resisting of concrete structures, increase the stiffness and durability of structures, and make full use of the high-strength performance of materials. So it has been widely used in constructional engineering, and there are notable social and economic benefits.Strengthening technology with externally prestressed tendons is a newly arisen course in modern prestressed structural system. When prestressed tendons are laid outside the cross-section of constructional members, it is easy to inspect, repair and replace tendons. It is an active strengthening method that can effectively increase the bending and shearing resistance capability of structural members. Domestic and international scholars make a great deal of experimental research on this method, which is mainly focused on applying prestress along the entire members. But constructional members can't fulfill functional requirement only because of local big cracks in most cases. It is unfavorable to the support section when midspan is strengthed along entire members, and it is unfavorable to midspan when support sections are strengthed. The stress concentration at transition location of fold-line tendons especially is formed. In the paper, local tension of prestressed tendons is used to strengthen indeterminate structures.The content of this paper is consists of these following aspects: Firstly, prestressed tendons and prestressed strengthening technology is summarized, then the performance of prestressed tendons, tension method and anchoring problem are discussed. And primary internal forces of indeterminate structures, resultant internal forces, secondary internal forces and computing method of secondary internal forces are analyzed and studied also. Secondly, design of tendon position and corresponding combination are made to strengthen single-span and multi-span beams of indeterminate structure and single-storied frame beam with local tension of prestressed tendons. On the base of the theoretical study and analyzation, secondary internal forces of different tendon position and corresponding combination are analyzed and computed. Furthermore, the calculation results are shown in the form of tables. Finally, the influence of position of local tension of prestressed tendons on the inner support of statically indeterminate beam and mid-span composite moment are discussed, and an optimizing layout method of prestressed tendons is supplied also, which makes composite moment of inner-support cross-section plus. Since the calculation method of strengthening members with local tension of prestressed tendons can extend to whole-line tension, it remedies the disadvantage of original calculation method (possibly needed local tension isn't considerated),and completes calculation method of strengthening technology with externally prestressed tendons.