Research On Externally Prestressed Strengthening Technology Of Shi Zui Bridge

In Our country, the reinforced concrete simply-supported T shape beam bridge were built in the60-70s of20th centuries, the main beam section size is too small, the load was designed lowly, and most of the highway bridge are still in commission, it hasn’t met the increasing needs of the traffic. In order to restore or improve the bearing capacity, reinforcement was needed urgently. At present, there are a lot of methods for reinforcement. Rational reinforcement method is used, it can improve the strength, stiffness and stability of the bridge structure, and meet the requirements of the carrying capacity of the structure. From the principle of view, external prestressing technology belongs to the range of active reinforcement, it can improve the bearing capacity and stiffness of the original bridge structure, close cracks of the original main beam structure, it can enhance the crack resistance and stability of the main beam. External Prestressing technology which is simple, economical and efficient, it have been widely used in the practice of strengthening works.At present, the study of using external prestressing tendons reinforced to support reinforced concrete T-beam bridge is insufficient. For example, the ahead of the simply supported reinforced concrete T-beam bridge beam which are varying degrees of disease, such as main beam cracks, the steel corrosion. Method of evaluation of the carrying capacity of the existing bridge has not been unified. How to choose a reasonable layout of the prestressing tendons in simply supported reinforced concrete T-beam bridge. The calculation of stress of external prestressing tendons, how to accurately calculate the loss of prestress and stress increment. In the evaluation of the reinforcing effect for calculation of load capacity, how to consider the secondary effects.Around a series of problems above, this paper focused on the following aspects:Firstly, Analyze the existing cracks in the bridge main girder. In accordance with the causes, the cracks are divided into structural cracks (stress fracture) and non-structural cracks in two categories. Analyze the causes of these two types of cracks and their harms to the main beam. After analysis and comparison, structural cracks are made as the major object for the main object of the bridge reinforced calculation and design eventually.Secondly, Identification the bearing capacity of Shizui bridge before it was reinforced. Identification the bearing capacity is divided into the existing value and the design value of bearing capacity, to use bearing capacity of the existing value is made as assessment index. In the calculation of the existing value of the carrying capacity, we should take into account the current state of the bridge, the main beam cracks, the concrete protective layer sapling area of the main beam which were caused by mechanical damage, reinforced the extent of corrosion and other factors. Thirdly, Analyze the internal force and deformation of reinforcement structure, when the externally pretested tendons were decorated by different linear. From the location of the prestressing tendon layout, number of tendons, and prestressing tendons and horizontal angular variation.Fourthly, Analyze stress factors of prestressing tendon, it is mainly from the choice of the tension control stress, prestress loss calculation and the calculation of prestressed incremental.Fifthly, Evaluation the reinforcement effect, calculation structural bearing capacity of reinforced bridge, and contrast reinforcement before and the ultimate bearing capacity of the structure after, and evaluate reinforcing effect of Shizui bridge.