Ultrasonic Imaging of Pre-tensioned Conrete Section Based on Extracting Ultrasonic Scattering Waves from Tendon

2020 Fiscal Year Final Research Report

• Project/Area Number: 18K04321
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 22020:Structure engineering and earthquake engineering-related
• Research Institution: University of Fukui
• Principal Investigator: Suzuki Keigo 福井大学, 学術研究院工学系部門, 准教授 (40546339)
• Project Period (FY): 2018-04-01 – 2021-03-31
• Keywords: 超音波探傷 / PC鋼材 / 初期腐食 / 画像化 / 信号処理 / 非破壊検査

Outline of Final Research Achievements

A non-destructive inspection method was proposed to determine the initial corrosion state of prestressed concrete tendons, which are difficult to observe directly. Ultrasonic waves with a center frequency on the order of kHz were incident from the concrete surface to acquire reflected waves from tendons. Although the boundary conditions between the surface of the tendon and concrete differ depending on whether the tendon is healthy or corroded, the difference is limited in the initial corrosion state, making it difficult to judge. This study solved this problem by applying signal processing by parasitic discrete wavelet transform (P-DWT). A demonstration experiment proved the effectiveness of signal processing. A steel rod in a concrete specimen was corroded by the electrolytic corrosion experiment. It became possible to differentiate the signal strength by about 30% between the image of the steel rod in the healthy state and that in the initial corrosion state.

Free Research Field

構造工学・地震工学・維持管理工学

Academic Significance and Societal Importance of the Research Achievements

プレストレストコンクリート内の鋼材は耐荷力上重要な役割を果たしている。初期状態の腐食の検知は外観目視では困難であり、非破壊的に可視検知できる本手法は社会基盤構造物の維持管理の高度化に寄与する。寄生的離散ウェーブレット変換による信号処理手法は、境界条件の微細な変化を捉えることができる。この手法ノイズ低減にも貢献するため、生波形からは判断しにくい条件下で、変化の徴候を抽出する必要のある検査対象物にも適用できる可能性を明らかにした。