Research And Application Of Prestressed Concrete Testing Method Based On Elastic Wave

Prestressed concrete bridges are widely used in the world.Uncompact reinforcement in grouting bellows will lead to rust and other problems,resulting in bridge damage and collapse accidents.structural concrete strength testing has attracted more and more attention from scholars at home and abroad.Several non-destructive testing methods commonly used in strength testing have their own advantages,but there are still some deficiencies.A method based on elastic wave to detect the strength of prestressed concrete is proposed.The defect of prestressing concrete is summarized and analyzed,and the conclusion that the strength of the defect is low and the velocity of elastic wave is low is drawn.Combined with the relationship between the velocity of elastic wave and compressive strength,a method of evaluating concrete strength based on the velocity of elastic wave is put forward.Based on the study of excitation,propagation and reception of elastic wave,the characteristics of first break wave and reflection wave are summarized,and the data processing flow of concrete strength detection is given.Elastic wave instrument using electromagnet vibration source as signal source and three-way roller piezoelectric acceleration detector as receiving device in concrete strength testing has the characteristics of stable energy,high frequency,large amount of data acquisition and high efficiency.It is suitable for long-distance and large-area nondestructive testing of concrete structure strength.For concrete surface strength detection,combining the numerical simulation of elastic wave with different surface strength models and the physical simulation of concrete model,a direct shear wave method suitable for surface defect detection is proposed to achieve horizontal resolution of 1 cm of wave velocity and two coverages of velocity value.It is proposed that when determining the coordinates of the low intensity area on the surface through the degree curve of the actual measurement speed.The coordinates of the starting point of the low intensity area are the coordinates corresponding to the point where the velocity curve starts to change plus half of the excitation receiving arrangement length.The coordinates of the ending point are half of the excitation receiving arrangement length corresponding to the coordinates of the point where the velocity curve ends and changes.For the detection of concrete internal strength,a reflection wave method suitable for concrete matrix and the detection of grouting defects in bellows is proposed.The longitudinal and shear waves are extracted by filtering,the energy in time direction is compensated by spherical diffusion amplitude compensation,and the energy in line direction is compensated by surface consistent amplitude compensation of concrete.The amplitude compensation is verified by physical simulation of concrete model.The effect is good.The stack velocity spectrum suitable for high-efficiency imaging is proposed by numerical simulation.The data after amplitude compensation are superposed horizontally.Combined with tilt factor,spherical diffusion factor and wavelet shaping factor,10 cm offset aperture is selected for amplitude-preserving diffraction offset superposition imaging on the data before amplitude compensation.Considering the spectrum characteristics of elastic wave,the imaging of low intensity region is processed by combining the amplitude and velocity characteristics,which makes the stacked section more accurate.In order to verify the practicability and accuracy of the concrete strength detection method with amplitude-preserving imaging,the self-made elastic wave instrument is used to detect the strength of the prestressing beam on the Wuhu light rail site,and the parameters are processed on the reference line without grouting bellows.The reflection axis of the bottom interface of the beam and plate is clear.The efficient imaging of all the lines proves that the elastic wave method has the capability of bridge detection.Practical significance.