| Summary: | 碩士 === 國立中興大學 === 土木工程學系所 === 98 === The purpose of this thesis is to investigate the application of the stress wave techniques to concrete plate thickness measurement. Five measurement methods are used. The first one makes use of the frequency response combined with the far distance reflection wave method (Method one). The second one uses an impact device able to record the start time of impact and a receiver sensing the vertical surface displacement (Method two). The third method adopts an impact device able to record the start time of impact and a receiver sensing the horizontal surface displacement (Method three). The forth method uses two vertical receivers according to ASTM C 1383 (Method four). The final one employs two horizontal receivers and follows the ASTM C 1383 test procedure (Method five). A comparison of the in-place measurement results among these five methods is made and the difference between the measurement values and the known thicknesses is discussed.
For the efficiency on measurement of concrete thickness, this thesis uses two sets of programs which are presented by graphic interface, called C1383-Modified, FF Plate Thickness Test Method for Method one and SEC_NDT_02.2_C1383 Plate Thickness Test Method for Method two 〜 five. The program C1383-Modified, FF Plate Thickness Test Method (Method one) adopts the travel time of the P-wave propagating from the impact point through the bottom reflection to the receiver at a point far away from impact and the thickness frequency of the plate and after measurement the velocity of internal P-wave and the plate thickness can be obtained simultaneously. The program SEC_NDT_02.2_C1383 Plate Thickness Test Method (Method two 〜 Method five) measures the surface P-wave velocity and the thickness frequency of the plate to estimate the thickness of concrete plates. Experimental results show that the accuracy of the thickness measurement depends on the accuracy of measurements on the thickness frequency and the wave velocity. Use of multiple measurement methods is of great help in making the measurement results reliable.
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