| The past few decades is the golden period of development of highway construction in our country, and therefore the bridge engineering construction level has been greatly improved. As the growing demand for the long-span bridge construction, prestressed concrete continuous rigid frame bridge with significant advantages such as high prestress strength,strong spanning capacity and strong overall stability has been widely recognized in the industry, and become the most common design options from the various bridge types. But with the increase of operating time, many continuous rigid frame bridges appear many defects and diseases due to various reasons in recent years,such as the problem of excessive mid-span deflection, a sharp increase in the box cracks and widespread crack of bridges, which reduce the actual bearing capacity of bridge,and have a serious influence on the safe operation and service life of bridges.Considering the higher cost of building new bridges, it is of great significance to research the causes of disease of bridges with defects but still in service and take certain measures to reinforce and maintain bridges according to the reasons.This paper was based on an instance of engineering of Hongling viaduct(right range) which located in expressway from Hegang to Dalian. It made a detailed study in the causes of two typical diseases of the prestressed concrete continuous rigid frame bridge( large mid-span deflection and cracking of box girder) by using finite element analysis software to establish the model of full bridge at first. The influence of shrinkage and creep of concrete, the cracking of box girder and longitudinal prestress in roof, bottom plate and web plate of box girder on mid-span deflection are analyzed in this paper and the difference between the deflection with and without consideration of shear deformations was compared at the same time. It also analyzed the influence of longitudinal and vertical prestress, temperature effect and the shrinkage and creep of concrete on the principal tensile stress of box girder, thus concluded the main cause of inclined cracks in web plate. Then a local entities model of the bridge is built to analyze the detailed characteristics of stress distribution in typical disease beam segment, after which the law of distribution and development of the cracks and the relationship between the formation of the crack and the high stress are verified.Secondly, combined with the existing related research in bridge strengthening,some of the most commonly used reinforcement technologies, which are proved to be effective in engineering practice are introduced from the function principle, technical characteristics and the scope of application, etc. The reinforcement technology include section-enlarging reinforcing method, reinforcing way of plastering steel plate,reinforcing way of bonding carbon fiber and external prestressing reinforcement technology. The actual reinforcement effects of each method are summarized bycomparing their simulation results. And the reinforcement effects of mixed reinforcement method combining various reinforcement technology are also compared at the same time, which provide a reference for the design of bridge reinforcement maintenance program in the actual project.Finally, this paper introduced the main diseases of Hongling Viaduct(right range)based on its detecting report, determined the causes of the diseases of the bridge combined with the previous theoretical research, and then puts forward the targeted strengthening maintenance program. Concrete reinforcement measures are simulated in the finite element model and the actual reinforcement effect is evaluated by contrasting the change of main reference index before and after taking reinforcement measures. The idea of this paper from the design of reinforcement scheme to the concrete implementation as well as the later appraisal of strengthening effect are worth using for reference for similar reinforcement maintenance program in practical engineering. |
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