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http://dx.doi.org/10.7843/kgs.2021.37.11.51

Natural Frequency Measurement for Scour Damage Assessment of Caisson Pier  

Nguyen, Quang-Thien-Buu (Dept. of Civil & Environmental Eng., Seoul National Univ.)
Ko, Seok-Jun (Dept. of Civil & Environmental Eng., Seoul National Univ.)
Jung, Gyungja (Korea Expressway Corporation Research Institute)
Lee, Ju-Hyung (Dept. of Geotechnical Engineering Research, KICT)
Yoo, Min-Taek (Korea Railroad Research Institute)
Kim, Sung-Ryul (Dept. of Civil & Environmental Eng., Seoul National Univ.)
Publication Information
Journal of the Korean Geotechnical Society / v.37, no.11, 2021 , pp. 51-60 More about this Journal
Abstract
River scour erodes the soil around the pier, reducing the lateral bearing capacity of the pier and lowering the stability of the structure. In this study, in order to examine the effect of scouring on the stability of the structure, an experiment was performed to measure the natural frequency of the pier according to the excavation of the surrounding ground. Impact vibration test was conducted on the pier with the caisson foundation of the Mangyeonggang Bridge, which is scheduled to be demolished. Accelerometers were attached to the top, center, and bottom of the pier and the acceleration responses were measured by hitting those three points. The experimental results showed that the top hit showed consistent and reasonable results of the acceleration responses according to the hitting position. The measured accelerations were converted to the frequency domain through Fast Fourier Transform (FFT), and then the natural frequency was determined. In addition, to analyze the scour effect on the natural frequency of the pier, the ground around the pier was excavated and the natural frequency change was analyzed. As a result, the natural frequency showed the decreasing tendency according to the excavation depth, but the decrease was small due to the large stiffness of the caisson foundation.
Keywords
Caisson foundation; Impact vibration test; Natural frequency; Scour;
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