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2018 Vol.34, Issue 11 Preview Page
November 2018. pp. 81-92
Abstract
For a marine bridge foundation construction, a large-circular-steel-pipe has been proposed for supporting vertical load and preventing water infiltration. However, a ship collision can adversely affect the structural stability. This paper presents a fundamental study on dynamic responses of the large-circular-steel-pipe by an impact load. In laboratory experiments, small-scaled steel pipe is installed in a soil tank. The soil height and water level are set to 23 cm and 25~70 cm, respectively. The upper part of the steel pipe is impacted using a hammer to simulate the ship collision. The dynamic responses are measured using accelerometers and strain gauges. Experimental results show that the strain decreases as the measured location is lowered. The higher frequency components appear in the impact load condition compared to the microtremor condition. However, the higher frequency components measured at the strain gauge located below the water level do not appear. For the accelerometer signal, the maximum frequency under the impact load is higher than that of the microtremor. The maximum frequency decreases as water level increases but it is larger than the maximum frequency of the microtremor. This study shows that strain gauge and accelerometer can be useful for evaluating the dynamic responses of large-circular-steel-pipes.
최근 해상 교량 기초 시공 중 차수 및 연직 하중을 지지하는 역할을 수행하는 대형 원형 강관 가설 공법이 제안되었다. 하지만, 대형 원형 강관의 시공 및 운용 중에 발생할 수 있는 선박 충돌과 같은 위부 요인은 구조물의 안정성에 악영향을 줄 수 있다. 따라서, 본 연구에서는 외부 충격에 의한 대형 원형 강관의 동적 반응을 평가할 수 있는 기법을 개발하기 위해 실내 실험을 통한 기초 연구를 수행하였다. 실내 실험에서는 해상에 설치된 대형 원형 강관을 모사하기 위하여 소형 모형 강관을 토조에 설치하였고, 토조 속 흙의 높이와 수위는 각각 23cm와 25cm로 설정하였다. 수위는 40cm, 55cm, 70cm로 변화시켜가며 실험을 수행하였다. 선박 충돌을 모사하기 위하여 모형 강관의 상부를 해머로 타격하였으며, 모형 강관의 길이 방향으로 설치된 변형률계와 상부에 설치된 가속도계로 신호를 측정하였다. 실험 결과, 변형률계로 측정된 변형률이 모형 강관의 상부에서 하부로 내려갈수록 감소하였다. 변형률계로 측정된 신호의 주파수는 충격이 가해지면 상시미진동 주파수보다 크게 증가하였지만, 수위 아래에 위치한 변형률계에서 측정된 주파수는 큰 증가를 나타내지 않았다. 가속도계로 측정된 신호의 최대 주파수는 충격이 가해지면 상시미진동 주파수보다 크게 증가하였다. 수위가 증가하면 최대 주파수는 감소하지만, 상시미진동 주파수보다는 크게 나타났다. 본 연구의 결과는 변형률계와 가속도계가 대형 원형 강관의 동적 반응 특성을 평가하는데 유용한 지표가 될 수 있음을 보여준다.
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Information
  • Publisher :The Korean Geotechnical Society
  • Publisher(Ko) :한국지반공학회
  • Journal Title :Journal of the Korean Geotechnical Society
  • Journal Title(Ko) :한국지반공학회 논문집
  • Volume : 34
  • No :11
  • Pages :81-92