Application of Impact-Echo Phase to Detect Reinforcing Steel Bar and Crack
Date Issued
2014
Date
2014
Author(s)
Lin, Li-Chuan
Abstract
The impact-echo test is a nondestructive testing technique for civil structures. In the test, the surface response of the target structure due to an impact is measured. Then, the Fourier transform is adopted to transform the signal from the time domain to the frequency domain. The frequencies of the peaks can be used to determine the size of the structure or the location of the defect. In practice, the inclusion of target structure is unknown. Therefore, it cannot infer the interfaces is crack or reinforcing steel bar only by observing the frequencies of peaks.
The purpose of this study is to analyze the phase characteristic of stress wave that comes from crack and reinforcing steel bar. Frist, progress the impact-echo test to obtain the impact-echo signal and remove surface wave of impact-echo signal by delaying the time origin. Then, use the Fourier transform to transform the impact-echo signal to frequency domain and find the phase of echo peak. Finally, identify the echo caused by crack or reinforcing steel bar by the phase and phase slope.
The explicit finite element methods was firstly adopt to simulate the stress wave propagation when stress wave encounter crack and reinforcing steel bar. Then, the model tests were used to verify the numerical results. From the numerical and experimental results, one can conclude that the phase of crack echo approximate to zero and the phase slope is high. The phase of reinforcing steel bar echo approximate to and the phase slope is small.
Compared to the conventional impact-echo data analysis, the proposed methods can not only determine the defect depth but also identify the defect that is crack or reinforcing steel bar.
Subjects
敲擊回音法
相位
非破壞性檢測
混凝土
裂縫
鋼筋
Type
thesis
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