Abstract:Prestressed concrete girder bridge is popular in engineering field for its advantages of good structural stiffness, smooth running and simple maintenance. However, in recent years, in the construction process or use stage of long-span prestressed concrete beam Bridges, there are generally a variety of diseases of different nature, the most common diseases are box girder cracking and long-term structural deflection; These diseases pose a threat to the durability and operation safety of Bridges, and even hinder and restrict the development of long-span prestressed concrete girder Bridges to a certain extent. In view of the diseases of existing long-span prestressed concrete beam Bridges, the causes of the diseases, the diagnosis of bridge damage, the repair and strengthening methods of damaged Bridges are urgent problems to be solved in the application of such Bridges. In this paper, the diseases of existing long-span beam Bridges in China are described. The causes of these diseases of long-span prestressed concrete beam Bridges involve design calculation, construction technology, maintenance management, material properties, etc. The causes of each typical disease are analyzed, and corresponding preventive measures are given, in order to benefit the actual project.

Abstract:3 Test results The author determined the free chloride ion content (the percentage of chloride ion in the mass of concrete) of the specimens after soaking and salt spray test, and the results are shown in Figure 6-8. Due to the selection of concrete mix materials before the test and strict control of the specimen making process, it is believed that the initial free chloride ion content of concrete is 0%.

Abstract:Steel pipe arch bridge is a common type of highway bridge, but arch rib concrete is a common disease of this kind of bridge. Aiming at this problem, this paper takes the excellent performance of high strength, low viscosity, high permeability, low temperature resistance and high flexibility grouting material in the simulation test as an example to illustrate the advantages of this material in the treatment of the arch rib of the steel pipe arch bridge. The research results of this experiment have practical application significance to the treatment of arch rib concrete caving disease.

Abstract:The system using two smaller diameter strand cable with swaging anchorage in the same anchorage zone can optimize the stress distribution of the anchorage zone and improve the security of the cable.At the same time, it is easier for maintaining and replacing.The system has been used in many bridges.

Abstract:Taking the Yongjiang Bridge reinforcement project of Nanning City as an example, the external prestress reinforcement measures were adopted and the finite element analysis program midas was used to analyze the external prestress reinforcement design. The results of calculation and engineering practice show that the external prestressing reinforcement method can effectively improve the internal force and stress distribution of the original structure, and increase the bearing capacity of each control section of the structure, especially the downwarping deformation of the free end of the beam. Therefore, it can be used as an important reference for the design and construction of similar external prestressed reinforced Bridges.

Abstract:Based on the anti-slip and anti-friction test method and test process of the cable saddle of Lassa Najin Bridge, the loading test principle of the epoxy gripping anti-slip anchorage device is proposed. According to the requirements of the anti-slip test plan, the epoxy gripping anti-slip anchorage device is tested, and the static anti-slip mechanical properties of the cable bridge tower anchorage structure of the low tower cable-stayed bridge are checked, and the test results are summarized and analyzed. The anti-slip and anti-friction performance of the saddle of the cable-stayed anchor cable is proposed from the aspects of design and construction.