Study On Stress Increment Of Continuous Rigid Frame Bridge Strengthened By External Cables

In recent years,along with the surge of traffic volume and heavy traffic other factors,some continuous rigid frame bridges have experienced a series of diseases in the actual operation process,which has affected their normal service functions and durability.As an active reinforcement method,the external prestressing technology can solve the problem of existing bridges effectively,and also change the internal force of the structure on the basis of reinforcement and unloading,so it is widely used in the reinforcement of continuous rigid frame bridges.As an important indicator,the external cable stress increment has a direct impact on the reinforcement effect of the bridge,so it has received widespread attention from the industry.At present,the theoretical model of the external cable stress increment research is basically aimed at the simply supported beam.The research results of the applicability of the continuous rigid frame bridge are still open to question.In addition,the existing research mainly focus on the ultimate state of the bearing capacity of bridges,and research on the normal service stage is less.In view of the above problems,this paper relies on the research project of Shaanxi Provincial Department of Transportation,“Key Technology Research of Long Span Continuous Rigid Frame Bridge Based on Life Cycle”(13-25K)and Promotion Project “Key Technology Application of Long Span Continuous Rigid Frame Bridge Promotion Research”(18-19T)to conduct research.Firstly,the ultimate stress increments of externally supported simply supported beams and continuous rigid frame bridges are calculated by the normative formula.Compared with the results of finite element analysis,it is found that the normative formula has some unreasonable points in the calculation of continuous rigid frame bridges.Then,based on this,the applicability of the standard formula for the ultimate stress increment of the external rigid frame bridge and the single-span reinforcement is studied respectively,and the revision methods for the standard formula of the external cable stress increment in different reinforcement conditions are proposed respectively.The calculation method of stress increment of external cable reinforcement continuous rigid frame bridge in normal use condition is derived by the energy variation principle,and the method rationality is verified.Finally,based on the external cable stress increment,the influence law of the four parameters such as steering block and anchor block reserve structure,external cable tension control stress and reinforcement time are studied.According to the research results,the corresponding design and construction suggestions are proposed.The results show that for the external cable reinforcement of continuous rigid frame bridges,the revised method of the ultimate stress increment formula and the calculation method of the stress increment under normal service state proposed in this paper are closer and smaller than the actual results,and can be used for the design and calculation of the bridge reinforcement accurately and safely;On the other hand,the external cable stress increment will show a certain regular change with the changes of various parameters,The research results can guide the design and construction of the continuous rigid frame bridge structure and external cable tension.Through the above research,it not only enriches the relevant theories of external cable reinforcement technology,but also provides reference for the similar design and construction work of reinforcement engineering.