| The structural safety of prefabricated concrete structures depends to a great extent on their assembly and construction technology.Grouting sleeve,as a common connection mode of assembly building structure system,its construction quality will greatly affect the bearing capacity of the joints and the overall performance of the structure.However,there is no effective non-destructive testing method for sleeve grouting construction quality at present.The guided wave nondestructive health testing of intelligent aggregate has the characteristics of high efficiency,low cost and wide application.It has been developed and applied in various testing fields.The main contents of this paper include the following aspects:(1)Based on ABAQUS finite element numerical model and the excitation signal modulated by Hanning window in MATLAB,the propagation state of guided wave in numerical model concrete members is analyzed,the propagation characteristics of Lamb wave in structures are given,and the basic ideas and feasible steps for its application in non-destructive testing of assembly joints are given.(2)By establishing a three-dimensional grouting sleeve finite element model,the specific influence mode and degree of different medium parameters on the test results were studied under different modes of single-delivery,single-delivery and different-delivery.According to the initial response time of the receiving point time domain signal,the overall performance of grouting sleeve with different shear groove number is judged;in the single receiving mode,the peak value in time domain decreases with the increase of grouting material density(2400kg/m~3-3900kg/m~3)and Poisson’s ratio(0.1-0.3);and the selection conditions of the optimum frequency and period of grouting sleeve under multi-media state,the propagation medium and the Poisson’s ratio are explored.The difference of structure will lead to the conclusion that the optimum frequency and period of guided wave selected by the model are different.Different defect locations and depths are manufactured by deleting elements.The guided wave propagation state and difference in grouting sleeve under different working conditions are discussed.The relationship between the peak value of defect echo and the increase of the damage rate of section is determined.When the damage rate of section is 100%,the peak value is obtained.The maximum ratio was 53.6%.(3)Embedded state is the actual working state of grouting sleeve.Firstly,the numerical model of grouting sleeve in pre-embedded state is established,and the optimum frequency and period of Lamb wave are selected.The variation characteristics of time-domain signals and the difference of guided wave propagation characteristics of grouting sleeve under the same excitation signals under the pre-embedded and vacuum conditions were investigated.The relationship between the different cross-section heights of pre-embedded concrete(0.4m-1.2m)and the echo peak values of defects at the receiving points was studied under the pre-embedded condition.The different defect lengths(0.02m-0.1m)were set under the pre-embedded condition.Grouting material,according to the propagation performance of grouting sleeve and the related characteristics of stress nephogram,the specific time of defect echo is judged.The detection results in defect components with different depths show that the peak value of defect echo increases with the increase of defect length of grouting material,and the trend is obvious,which proves that Lamb wave is applied to grouting.Nondestructive testing of sleeve is feasible. |
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