Study On Stress Detection Of Prestressed Structural Steel Strand Based On LC Resonance

China is a big country of Bridges,and prestressed concrete bridges play an important role in the service bridges.With the growth of operation time,problems such as bridge midspan deflection caused by the loss of longitudinal prestress gradually appear,which affect the safety and comfort of driving,and even cause the bridge collapse,and threaten the personal safety and national economy.As the prestressed provider of prestressed concrete structure,the effective prestress of steel strand directly affects the performance of the whole structure.However,due to the mutual influence of various prestress losses,it is very difficult to accurately calculate the effective prestress of steel strand,and the safe operation of the structure can be guaranteed by effective prestress detection means,so the prestress detection is affected by To the engineering and research community’s widespread concern.Although all kinds of prestress detection methods have achieved some research results,there are few methods that can be used to monitor the effective prestress,high precision and good stability of all kinds of structures in service for a long time.The method of steel strand stress detection based on LC resonance regards the steel strand as an inductive element connected to LC oscillation circuit,and realizes the stress detection of steel strand by detecting the resonance frequency of oscillation circuit,which has a broad development prospect in the field of effective prestress detection of structure.In this paper,based on the research of the method to detect the stress of the bare steel strand,the stress detection of the unbonded and bonded prestressed steel strand in the structure is explored.The purpose of this paper is to verify the feasibility of the method based on LC resonance to detect the stress of the prestressed steel strand in the structure,and to detect the effective prestress or prestress loss of the prestressed steel strand in the structure The results of this study provide reference.The research content mainly includes:(1)The steel strand is regarded as the inductance element of spiral coil in LC oscillation circuit.From the point of view of mechanical deformation caused by stress,the inductance model of steel strand is established,and the force frequency model of bare steel strand is established;(2)The stress increment and distribution of unbonded and bonded prestressed tendons are analyzed,and the force frequency model of prestressed steel strands is established;(3)Carry out the force frequency model verification test of bare steel strand,fit the force frequency function curve of bare steel strand,and verify the accuracy of the force frequency model of bare steel strand;(4)Carry out the force frequency model verification test of unbonded and bonded prestressed steel strand,verify the stress distribution of unbonded and bonded prestressed steel strand in the structure,establish the fitting formula for the calculation of the test stress of unbonded and bonded prestressed steel strand,analyze the error between the test stress and the measured stress,and verify the method of structure detection based on LC resonance The feasibility of internal prestressed steel strand stress;(5)Combined with the measured stress and frequency data of bare steel strand,unbonded and bonded prestressed steel strand,the influence of structure on the resonance frequency of steel strand is analyzed.