Study On Ultrasonic Guided Waves Testing Method For Weak Bonding Interface Defects Of Steel-Concrete Structure

Steel-concrete structure has the advantages of solid structure,stable reliability and saving in material.It is widely used in various types of infrastructures,such as nuclear waste storage tanks,super high-rise buildings,and high-speed rail bridges.However,various damages are unavoidably generated in this composite structure when it is affected by the environmental factors,and the most typical defect is located at the bonding interface between steel and concrete.The appearance of defects in the bonding interface will lead to the deterioration of the overall performance and endanger the structural service safety.It can avoid major disasters and ensure the safety of infrastructure when the defects are found early and the structural maintenance is conducted.Therefore,focused on characterizing the weak bonding interface defects in a non-destructive testing way,this paper proposes a fast detection method based on ultrasonic guided waves.The main research contents are as follows:?1?The theoretical propagation law of ultrasonic guided waves in the steel-concrete structure is studied,and the interaction law between the S0 mode and the defect located at the bonding interface is analyzed.According to the theoretical propagation model of the single-layer plate structure,the theoretical dispersion curve is obtained by the potential function method.The multi-layer theoretical propagation model of steel-concrete structure is established by the global matrix technology,and the imaginary wavenumber is calculated.The results show that the imaginary part of the wavenumber under different bonding states is obviously different,and the attenuation law of S0 mode can be used to characterize the interface bonding state in steel-concrete structures.?2?The sensitivity of different ultrasonic guided wave modes to interface bonding defects is analyzed on the basis of a finite element model of sound propagation in steel-concrete structures.The finite element results show that the A0 mode does not change significantly under different bonding conditions,while the S0 mode changes significantly.The ratio of A_S0/A_A0 is used to characterize the bonding state of the steel-concrete structure.The ratio will increase when the bonding strength between the steel layer and the concrete layer gradually weakens,which can quantitatively characterize the state of the weak bonding interface.?3?An ultrasonic guided wave experiment system for evaluate the weak bonding interface state of steel-concrete structures is designed,and the feasibility of the method has been verified through experiments.The experimental results reveal that the air coupled approach can excite and collect ultrasonic guided wave signals in the steel-concrete structure.The intensity of the A0 mode basically does not change significantly,while the intensity of the S0 mode gradually increases when the bonding strength gradually weakens.The waveform index determination method can be used to better characterize the bonding state of the steel-concrete bonding structure.