Detecting the reinforced concrete beam/column joints by ultrasonic wave and impact-echo methods
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摘要: 本文用超音波法及敲擊回音法分別以斜向對打量測實體柱、不同厚度之塊狀試體、十字形試體及實體梁柱接頭之壓力波波速值,并與上述各試體之超音波直接對打量測的壓力波波速值作比較,以評估斜向對打量測波速壓力波之準確性,藉以探討以斜向對打量測波速壓力波值來檢測梁柱接頭混凝土質量之可行性.試驗結果顯示:超音波法于面寬40 cm之實體柱量測,當接收器偏距大于40 cm時,其波速值會明顯下降;但敲擊回音法以直徑3 mm鋼球作敲擊源,接收器偏距超過70 cm波速值才會呈現下降趨勢,以直徑6mm鋼球做量測則接收器偏距可達100cm,若以直徑9mm鋼球或鐵錘做量測,接收器偏距達300 cm時,波速值仍未呈下降趨勢.各試體之試驗結果皆顯示,超音波法之量測波速值基本上隨接收器偏距增加而下降,但敲擊回音法之波速值卻不受偏距影響,其波速值與超音波直接對打值比較,誤差皆在±3%以內.Abstract: This paper used an ultrasonic wave method and an impact-echo method to measure pressure wave velocities in full scale columns,block specimens with different thickness,cruciform specimens,and beam/column joints by obliquely placing transducers on the opposite faces.The results were then compared with those by direct measurement using an ultrasonic device to evaluate the accuracy of oblique measurement.The feasibility of quality evaluation for the concrete at the beam/column joint using the measured pressure wave velocities by oblique measurement was discussed.The test results showed that,the measured wave velocity went down sharply when the wave receiver deviated more than 40 cm for the measurement on a 40 cm width full scale column by the ultrasonic wave method.However,the measured wave velocity would begin to go down when the wave receiver deviated more than 70 cm using a 3 mm diameter steel ball as the impacting wave source by the impact-echo method.Using a 6 mm diameter steel ball,the deviation distance could reach up to 100 cm.Using a 9 mm diameter steel ball or a small hammer,the measured wave velocity would not go down even when the deviation distance was up to 300 cm.All test results on the specimens showed that,the wave velocity measured by the ultrasonic wave method basically went down when the deviation distance of the receiver increased,but the wave velocity measured by the impact-echo method was not affected.When compared with ultrasonic direct measurement,the wave velocity errors of the impact-echo method were well within ±3%.
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Key words:
- reinforced concrete /
- joints /
- ultrasonic waves /
- impact-echo method
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