Research On Prestressed Detection Technology Of The Steel Strand Based On Frequency Method

With the continuous development of prestressed technology, prestressed concretestructures have been widely applied in the concrete bridge, the health and safety issuehas attracted more and more attention. Steel strand is the key component to bear loadsin prestressed structure, its health status directly affects the durability and safety ofprestressed structure. In the process of prestressed steel strand tensioning andbridge operation, due to the influence of material properties, construction conditionand the environmental conditions and other factors, the concrete bridge will produceunpredictable prestressed loss, resulting in the prestressed level decreased andnonuniform prestress distribution. Once the failure of the prestress of steel strand, itwill bring a huge security hidden trouble to the structure, influence of structuraloperation performance. Therefore, to realize the effective prestress of the prestressedsteel strand in engineering is very important.At home and abroad strand prestressed detection commonly used methods are:Strain gauge paste method, Pressure sensor under anchor detection method, Strandsensor detection method, Magnetic flux detection method, Fiber grating detectionmethod,Ultrasonic guided wave detection method and mass of equivalence method.These measurements, affected by the number of sensors, the measuring conditions, theinstallation process and other factors have their defects. Some testing methodsinterfered by various factors, measurement is not accurate; some expensive, can not bewidely used in practical engineering; some will cause a certain degree of damage to thestructure, the measured data is not accurate or not adequately, so it needs further study.The thesis discusses various prestress detection methods of the steel strand athome and abroad, and presents a new nondestructive testing method-Research onprestressed detection technology of the steel strand based on frequency method. Thedetection principle of frequency method is firstly studied, and find out thecorrespondence between the stress of prestressed steel strand and the oscillationfrequency, and then designed a set of experimental system for prestressed detection.Stress loading and unloading experiments were also carried out by the prestresseddetection. And the comparison between experimental results and theoretical study waspresented, Thus verifying the correctness of prestressed detection principle based onthe frequency method. Finally, the impact factors of the prestressed loss were analyzed and discussed, and the frequency detection technology in practical application arebriefly described.Through a large number of experimental results show that the prestresseddetection system has high sensitivity; structure of the detection system is simple, lowcost, easy to operate; conditions are less demanding on the field; fast detection, highdetection efficiency, and it provides a new idea, new method for prestressed detectionof the steel strand in concrete structure.