Study On Prestressed Loss Assessment Of Beam Bridge Structure Based On Fusioning Deflection And Frequency

The effectivity of prestressing tendons are directly related to the reliability,applicability and viability.Existing prestress force and the actual stress in tendons have close connection with the active state of pretressed concrete structure,so the detection of pretressed loss is the important part of the health monitoring and detection of prestressed concrect structure.This paper will embarks from the overall performance of the structure,appling the static and dynamic characteristic component of prsetressing loss delection and evaluation.This paper estabishes the method,which combines the structure dynamic charcteristics and the deformation to study the existing prestress of prestressed concrete bridge.Firstly,embarking from of the static aspect,the paper analyses the factors that affect down delection in the midspan of the prsstressed bridge.The relationshiop between the deflection and the prestressing loss has been estabished and the formular for calculaing deflection under different form of prestressed reinforcement in the form of prestressing tendons has been estabished.Secondly,analysising of dynamic characteristics,the influencing factors of bridge structure natural frequency is been analyzed.The frequency calculation formula under different form of the prestressing tendons has been estabished using of the existing self-vibration frequency formular of the prestressed simple girde.The coupling frequency and deflection of prestressed loss evaluation equationhan has been obtained,on the basis of the relationship between static and dynamic stiffness.And finite element simulation and experimental beam validate the rationality of the method.To do this:In this paper,the following work.1.During analysingt the factors of the excessive deflection in the midspan draws a conclusion that prestressing losses caused midspan is an important factor.In the analysis of the influence of the prestress on the deflection of the bridge,It is concluds that the deflection of the bridge structure is not only related to the prestressing force,but also to the layout of the prestress.2.The prestressed concrete beam is regarded as a composite body of the compressed concrete beams and the tensioned steel.The results can be seen by the frequency derivation:the self vibration frequency of prestressed concrete beams with compressed concrete beams and the tensioned steel is the same with the ordinary concrete beam.The main reason is the prestressing force changs the elastic modulus.This paper summarizes the domestic and foreign scholars for prestressed concrete beam flexural stiffness correction formula.And from the static and dynamic stiffness of the structure,the relationship between deflection,frequency and the prestressed of the concrete beam.The prestressing loss assessment equation in different force stage has been obtained.3.Using ANSYS finite element analysises the static and dynamic characteristics of the test beams and establishes different fabric reinforcement and different eccentricities test beam model to make up for the shortcomings of the test beam data and assess the feasibility of the method of proof from the simulation aspects.4.The static and dynamic test of three prestressed concrete simply supported beam without bonding are made.Sorting test data substituts into the coupling equation fingding that error calculated value and actual tension in addition to the small prestress value(N = 20 kN)is large,other condition difference is within 6%.The static and dynamic stiffness ratio coefficient K=1.135 is obtained from the experimental results.And Sorting the coefficient and the existing experimental data into coupled equations,the feasibility of the method is proposed based on the dynamic stiffness ratio of K and the fusion deflection and the frequency assessment of prestress losses,from the point of view of the results.