Application Research On The Externally Prestressed Strengthening Technique In The Continuous Rigid-frame Bridge

The continuous rigid frame bridge strengthened with external prestressing have special advantages in improving the carrying capacity, restorating the structural shape, and increasing the compressive stress reserves of the main beam. Excessive mid-span deflection and concrete cracking of main beam are the main diseases of the old continuous rigid frame bridge. So it is necessary to study the external prestressing strengthening technique in the continuous rigid frame bridge. In this paper, the external prestressing strengthening technique is studied with the disease mechanism analysis of the continuous rigid frame bridges, the mechanic properties of the external prestressing strengthening, the construction monitoring and the evaluation of shtrenthening effect for the external prestressing strengthening project of Chongqing Jiangjin Yangtze River Highway Bridge. It will provide some reference for the similar strengthening project.Firstly, the disease mechanism, the externally prestressed system and the strengthening mechanism of the external prestressing strengthening were analyzed. The design method was proposed through the loss compensation of the bottom longitudinal prestress. Then the load-carrying characteristics, the dynamic characters and the librating dampment were probed.Secondly, a structural damage model was proposed through fitting the deflection and stress based on the strengthening project of Chongqing Jiangjin Yangtze River Highway Bridge and its diseases mechanism. The strengthening design, the prestressing optimization and structural analysis were performed as well. Then the construction monitoring was designed and performed for this strengthening project. The modeling simulation and the monitoring results shows that the structural damage model is excat and effect to meet the requirements of the calculation of the carrying capacity of the old bridge. The result also shows that the externallyly prestressing strengthening can greatly increase the compressive stress reserves, decrease the main tensile stress and restorating the structural shape.Thirdly, the study has sussesfully performed the external prestressing strengthening project of Chongqing Jiangjin Yangtze River Highway Bridge. Many strain and deflection data are recorded from the long-span continuous rigid frame bridge strengthened with the prestressing. Some accumlated experiences can be applied to the similar strengthening project.