Research On Strengthened Old Bridges By Converting Simply Supported System Into Prestressed Continuous System

Reinforced concrete bridge structure will get aging or damage with the time. In addition, the use frequency of these structures and the load on them are increasing with the development of economy and society. Hence, the durability and bearing capacity of these bridges are reducing which resulted in a large number of old or dangerous bridges in China. If not properly handled, these bridges will hinder economy development and bring property and safety of life more of a threat to the human. However, to rebuild these bridges will cost a lot of manpower and material resources and increase the burden on society. Therefore, engineering and technical personnel attaches more and more importance to strengthening the old bridges.Converting simply-supported system to continuous system is one of the methods for reinforcing old bridge often used According to the different methods of continuous, it can be divided into a variety of forms. Among them, converting simply-supported system to prestressed continuous system has the best effects.This paper based on a bridge in Jingha highway which was strengthened by converting its simply-supported system to prestressed continuous system. The paper mainly includes two parts which are simulation calculation with Dr. Bridge and data processing and analysis according to the load test results. Specific contents are as follows:1. The bearing capacities of the structure respectively before and after reinforcement using the finite element software Dr. Bridge are checked. Checking reference is based on the general specifications for design of highway Bridge and culverts JTG D60-2004 and present code for design of highway reinforced concrete and prestressed concrete Bridges and culverts JTG D62-2004. In the calculation results, on the one hand, it is checked whether model meet the specification requirements. On the other hand, respectively extract and analysis the dead load and live load effect on the key section are extracted and analyzed. The results show that the structure can’t meet the specification requirements before reinforcement. However, it can completely meet the specification requirements after reinforcement by converting system and has good structural safety reserve. In addition, this paper also extracted moment and shear design values on key section from operation results before and after structure reinforcement to comparison and analysis. The results show that the moment design value after reinforcement decreases, and the shear design value increases. This is the result of adopting prestressed continuous on the pier top.2. This old bridge had been tested by load respectively before and after reinforcement in detail. This paper processed and analyzed the data of these two load tests mainly containing structural constant deflection, experiment load deflection and the stress and strain under load. After the data processing, results of the load tests show that its stiffness and stability are increased greatly after the structure reinforcement. Test load --deflection effect and the effect of the stress and strain are significantly reduced, which proved the superiority of this kind of reinforcement method again.