Measuring the Thickness of Concrete sStructure by the Stress Wave in Time Domain

• Main Authors: LI-ZHEN CHEN, 陳麗貞
• Other Authors: Yiching Lin
• Format: Others
• Language: zh-TW
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/98766261822087714523

碩士 === 國立中興大學 === 土木工程學系 === 88 === The objective of this thesis is to develop a new nondestructive technique for determining the thickness of plate-like concrete structure. The technique proposed in this thesis makes use of stress waves and signal analysis in time domain to get insight into the behavior of reflected P-wave, which travels into the structure and reflected from the bottom boundary. Combining identification of P-wave arrival time with the P-wave speed in a two-step procedure provides means for measuring plate thickness. Unlike the method proposed in ASTM C1383 using spectral analysis, the technique proposed in this thesis is an alternative technique for measuring the plate thickness. The thesis performs both numerical and experimental studies. Results show that the distance between the impactor and the receiving transducer must be appropriate to make the signal caused by the arrival of the P-wave reflected from the bottom surface of a plate can be obtained to avoid the interference from the arrivals of the stress waves propagating along the surface. When the distance between the impactor and the receiving transducer is short, the stress waves propagating along surface such as P-wave, S-wave and R-wave arrive at the transducer earlier than the P-wave reflected from the bottom surface. When the R-wave arrives at the transducer it causes a relatively large downward displacement followed by an overshoot in the waveform at the end of the R-wave. However, the downward displacement caused by the arrival time of reflected P-wave is significant to make its arrival identifiable in the waveform. Combining the arrival time of the reflected P-wave with the P-wave speed make it feasible to measuring the thickness of plate-like structures.