Detection Of Sleeve Grouting Connection Defects In Fabricated Structural Joints Based On Ultrasonic Guide Waves

In recent years,the state has repeatedly emphasized the need to promote innovation in construction methods,continuously promote the development of prefabricated buildings and prefabricated components and their application in practical engineering.The connection of the horizontal and vertical stress ribs in the prefabricated building is the key factors to ensure the good mechanical properties of the fabricated structure,and it has become the main reasons for restricting the application of the prefabricated building.At present,the reinforcing bars of prefabricated building can be spliced by a grout-filled coupling sleeve or lapped in grout-filled hole,and the former can be used more widely and reliably because of its non-restriction by the diameter of the spliced bar and the height of the building.However,in the actual construction process,due to the irregularity of construction,grouting defects are easily formed in the grout sleeve.Grouting defects will reduce the stability of the components and structures,causing structural damage and component damage to varying degrees.Therefore,the safety inspection and safety evaluation of grouting defects is crucial to the development of fabricated buildings.In this paper,the ultrasonic guided wave is used to detect the grouting sleeve structure with different grouting defects.And the attenuation characteristics of the guided wave are used to quantitatively analyze the grouting defects in the grouting sleeve and obtain the corresponding quantitative indicators.Finally,based on the monotonic tensile test of the grouting sleeve reinforcement connection,this paper analyzed the relationship between the degree of defect and the connection performance of the grout sleeve,evaluated the connection performance of the test piece by damage index and verified the feasibility,accuracy and applicability of using ultrasonic guided waves to detect grouting defects.The main research contents are summarized as follows:(1)The axisymmetric model of the grout sleeve was established by Ansys software.By axisymmetric model,the propagation rule of the ultrasonic guided wave signal in the grout sleeve was studied,and the guided wave signal propagation path analysis and signal energy diffusion analysis were completed.The influence of signal cycle number and signal frequency on the detection results of guided waves is analyzed and compared.And based on this,the selection basis of the simulation and experimental excitation frequency is given.(2)Six specimens of different defect lengths are established in this paper.The piezoelectric components are mounted on bars embedded in grout sleeve as sensors and actuators to generate the signal.By these way,paper investigates the effects of grouting defects on guided wave signals by experiments and simulations.In this paper,guide wave attenuation is combined with wave average energy density,and the influence of grouting defect on the guided signal energy is theoretically analyzed.The effects of grouting defect changes on guided wave signal energy is characterized by signal time domain energy,first wave amplitude,wavelet decomposition and wavelet packet decomposition.Two parameters are calculated from differences between responses of damage structure and those of healthy ones and used to indicate the bonding damages.The test results show that the WDI values and DI values increase significantly as the defect length increases,and the debond damage between the rebars and grouting material can be detected accurately.(3)The evaluation of sleeve grouting connection based on ultrasonic guided wave is studied.At first,the monotonic tensile test of the test piece was completed using an MTS machine.The influences of grouting defects on bearing capacity and deformation capacity were analyzed.The test results show that the grouting defects will reduce the axial tensile load capacity of the steel bar.Then,through the analysis of guided wave signals under different load conditions,the relationship between the defect indexes and the mechanical properties of the defective test piece is established.The idea of using ahp to complete structural health assessment and damage assessment is put forward.The results show that The defect index can be used to evaluate the health condition of the specimen.