Experimental Study On Acoustic Characteristics Of Concrete Based On HHT

On the basis of research on the ultrasonic properties of concrete, in the recentlyyears, done by many scholars and experts home and abroad, the methods of model test,signal analysis, statistical analysis and so on are used to deeply study the ultrasonicproperties of concrete under uni-axial loading conditions. The statistical relationshipbetween ultrasound and stress in concrete is got and the aggregate size, the ratio ofwater and cement and the sand ratio, which are the most sensitive to the relationshipbetween ultrasound and stress, are put forward. The main work of this thesis is asfollows:1. Based on the analysis of various factors affecting the acoustic pulse signal inconcrete, the main factors simulating the correlation of ultrasound and stress inconcrete materials are presented and the cross combination of these factors are done tomake a total of45specimens under15kinds of conditions, with which, acoustic testunder different loading conditions is done. All the test data are analyzed by usingdigital signal processing technology so as to lay a certain test foundation for findingthe components sensitive to the ultrasound and stress in concrete.2. On the basis of model test, HHT theory and such Matlab software, relatedprograms are written to process the acoustic signal in concrete. Then the method ofprocessing the acoustic signal in concrete is established, which is used to analyze thecorrelation of each acoustic parameter and stress. Finally, acoustic spectral parameterswhich are the most sensitive to the change of stress are obtained and they are weightedpeak of instantaneous amplitude, weighted area of marginal spectrum and weightedarea of instantaneous energy spectrum.3. The method of processing acoustic signal, put forward in this thesis, is adoptedto process acoustic test signal in the concrete with different aggregate sizes, differentratios of water and cement and different sand ratios. By analyzing the sensitivity ofacoustic parameters and stress in the concrete under different conditions, thecomponents, which are the most sensitive to the ultrasound and stress in concrete, areachieved.4. According to the components, which are the most sensitive to the ultrasoundand stress in concrete, concrete specimens are newly made and the changes in theinternal structure of the concrete specimens, which are under cylic loading (in the lowstress state) conditions, are studied. The changes of weighted peak of instantaneous amplitude, weighted area of marginal spectrum and weighted area of instantaneousenergy spectrum with stress, after cylic loading, are comparatively analyzed.