Journal of the Korean Geotechnical Society (한국지반공학회논문집)

Korean Geotechnical Society (한국지반공학회)
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A Study on Damage Assessment Technique of Railway Bridge Substructure through Dynamic Response Analysis

동적 응답 분석을 통한 철도교량 하부구조의 피해평가기법연구

  • Lee, Myungjae (Railroad Structure Research Team, Korea Railroad Research Institute) ;
  • Lee, Il-Wha (Advanced Infrastructure Research Team, Korea Railroad Research Institute) ;
  • Yoo, Mintaek (Railroad Structure Research Team, Korea Railroad Research Institute)
  • 이명재 (한국철도기술연구원 철도구조연구실) ;
  • 이일화 (한국철도기술연구원 첨단인프라융합연구실) ;
  • 유민택 (한국철도기술연구원 철도구조연구실)
  • Received : 2021.10.15
  • Accepted : 2021.10.28
  • Published : 2021.11.30
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Abstract

In this study, scale down model bridge piers were fabricated and non-destructive experiments conducted with an impact load to determine scours in the ground adjacent to the bridge piers using the natural frequency of the bridge piers. Three scale-model bridge piers with different heights were fabricated, and they penetrated the ground at a depth of 0.35 m. The scours around the bridge piers were simulated as a side scour and foundation scour. The experiments were conducted in 13 steps, in which scouring around the model bridge piers was performed in 0.05 m excavation units. To derive the natural frequency, the impact load was measured with three accelerometers attached to the model bridge piers. The impact load was applied with an impact hammer, and the top of the model bridge pier was struck perpendicularly to the bridge axis. The natural frequency according to the scour progress was calculated with a fast Fourier transform. The results demonstrated that the natural frequency of each bridge pier tended to decrease with scour progress. The natural frequency also decreased with increasing pier height. With scour progress, a side scour occurred at 70% or higher of the initial natural frequency, and a foundation scour occurred at less than 70%.

본 연구는 교각의 고유진동수를 통해 교각에 인접한 지반의 세굴 발생여부를 판단하기 위해 축소모형교각을 제작하여 충격하중을 이용해 일련의 비파괴 실험을 수행하였다. 축소모형교각은 길이별로 총 3개의 교각을 제작하였으며, 관입깊이는 0.35m로 일정하게 지반에 관입하였다. 세굴은 크게 2가지로 교각의 측면세굴과 기초바닥세굴을 모사하였으며, 0.05m씩 굴착하여 단계별로 step 0에서 step 12 까지 총 13단계의 실험을 모든 교각에 대해 수행하였다. 또한 고유진동수를 도출하기 위해 모형교각에 총 3개의 가속도계를 부착하여 충격하중을 측정하였다. 충격하중은 impact hammer를 사용하였으며, 타격방향은 모형교각 상단을 교축직각방향으로 타격하였다. 이 때 측정된 가속도 값을 바탕으로 고속 푸리에 변환(FFT)를 이용해 세굴진행도에 따른 고유진동수를 산정했다. 그 결과 세굴이 진행됨에 따라 모든 교각의 고유진동수는 감소하는 경향을 보였다. 세굴이 진행됨에 따라 최초 고유진동수의 70% 이상 수준에서는 측면세굴, 70% 미만에서는 기초바닥세굴이 발생하는 것을 판단할 수 있었다. 이 결과를 토대로 전도에 대한 안전율과 비교하여 교각기초의 피해정도를 분석할 수 있었다.

Keywords

Acknowledgement

연구는 한국철도기술연구원의 주요사업(PK2103B2) 연구비 지원을 받아 수행되었으며, 국토교통부/국토교통과학기술진흥원의 지원으로 수행되었습니다(21SCIP-C155167-03: MT21027).

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