Research On Detection And Reinforcement Of Large-span Prestressed Concrete Continuous Rigid-frame Bridge

Large-span prestressed concrete continuous rigid-frame bridge is one of the widely used bridge type in our country. The building size and the number of it are in the front rank of world. But, with the increase of service life and traffic volume, the deflection of main girders increases abnormally, and web plates and bottom plates are cracking, which attract extensive attention of engineering community.Combined with several typical engineering projects of large span prestressed concrete continuous rigid-frame bridges, this article summarized the existing prestressed rigid-frame bridge detection methods, focused on the prestress measuring, interior defects test in concrete and long-term deformation detection method, and presented the procedure and key points in the process of detection. Meanwhile, an demonstration was given in this article in combination of a specific test instance.For common diseases like deflection in the mid span and cracks on box girders appearing on large span prestressed concrete continuous rigid-frame bridges, the reasons were analyzed from the theoretical calculation, structure design, construction technology and environmental temperature changes. According to the cause of disease, this article put forward a method to suppress main girder deflection by applying external prestressing, changing bridge structure system and removing load.A 210 meters long prestressed concrete continuous rigid-frame bridge, after operating for 4 years, had diseases including deflection in the mid span and cracks on box girders. Based on the engineering example, contents of test and detection method of continuous rigid-frame bridge were described and two sets of evaluation system were used to evaluate the test results, which verified the conformity of assessment results. This article proposed to increase eight 19Φs15.2mm external prestressed reinforcements in the box girder webs due to detailed analysis. Calculation and analysis showed that the effect of reinforcements was obvious and the main span deflection was declined. After reinforcements, the theory result of midspan deflection is about 1.7cm. Stress state on mid-span and deck of main beam are improved, and the principal tensile stress of the web also decreased to some extent. Due to analysis of reasons for cracks on the web, roof and floor of bridges, the method of pasting CFRP or steel plates was used to reinforcement.Aiming at the diseases of large span continuous rigid-frame bridge, a complete set of technology which includes in-situ test method, technical condition evaluation method based on the test results and reinforcement method was studied. This article expounds the existing detection methods of prestressing system, and recommends the detection proces of large span prestressed concrete continuous rigid-frame bridges. Through the comparison between 《Code for Maintenance of Highway Bridges and Culverts》(JTG H11-2004) and 《Highway Bridges Technology Status Evaluation Standard》(JTG/T H21-2011), some recommendations and opinions are given on their usage from the perspective of applicators. Combined with analysis of disease cause of large span continuous rigid-frame bridge, this article proposes the common reinforcement methods, and expounds in detail of external prestressed strengthening method. At the end of the article, the complete set of above-mentioned technology is analysed and verified through a typical case.