| 講演要旨(和文) | | 筆者らは，グラウンドアンカーの残存引張り力を非破壊で計測する方法を開発し，既設アンカーでの実験によって，その適用可能性を示してきた．この方法は，緊張力が作用するアンカー自由長の固有振動周波数から，アンカーを弦と考えて，緊張力を推定するものである．今回，実物大のグラウンドアンカー模型を利用し，自由長の固有振動周波数から緊張力を推定する上での基礎的な事項について実験で確認した．この模型は，自由長部が気中に露出しているため，自由長の直接加振や受振が可能である．まず，自由長の自由振動の周波数を調べたところ，弦と見なし得ることがわかった．したがって，自由長の固有振動周波数を測定することができれば，緊張力を正確に推定できることがわかった．また，余長加振・余長受振の場合，スウィープ加振を一旦停止し，ノイズの少ない状態で測定すれば，微弱な自由長振動を測定できる見込みを示した． |
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| | 講演要旨(英文) | | The authors proposed a new method of non-destructive evaluation for residual load of ground anchors by using the frequency of free vibration of the tension length as a "string". Although the applicability of the method was confirmed at a real ground anchor slop, we didn't know if the tension length really vibrated as a string. This time, mock-up experiments were conducted to clarify the vibration characteristics of the tension length by using three different types of anchors and applying five different tensioning loads. We found that the frequency of the free vibration generated in the tension length is really the same as a string. This shows that we can estimate the tensioning load correctly from the frequency of free vibration of the tension length. In addition, we tried to measure the frequency by an accelerometer attached at the extra length of the anchor. We successfully measured the frequency by the trial in which the sweep generation stopped before measuring time so as to detect the small signals more clearly. |
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