| Summary: | 碩士 === 朝陽科技大學 === 營建工程系碩士班 === 89 === Prestressed concrete has been widely applied to structures such as bridges and large building roofs. Due to creep, concrete shrinkage, stress relaxation, and many other causes ,the stress level tends to decrease after a long period of time. This research focuses on the measurements of a tendon in a structural element. Based on the ultrasonic time-of-flight measurements, the correlation between stress level and ultrasonic signals are studied.
Delay in the ultrasonic signal is observed when the stress level of the tendon is increased. More delay in arrival time can be found and is associated with a higher stress level. Analysis in the frequency domain also shows greater attenuation in signals obtained at higher stress levels. Initial attempt based on a simple bandpass filter, however, fails to surpass the signal noise obtained from an unstressed steel bar.
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