Journal of the Korean Geotechnical Society (한국지반공학회논문집)

Korean Geotechnical Society (한국지반공학회)
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Establishment of Testing Method for Abutment Scour Stability by Real-scale Model Test

실대형 교각 실험을 통한 교각 세굴안정성 평가 실험 기법 정립

  • Lee, Myungjae (Railroad Structure Research Team, Korea Railroad Research Institute) ;
  • Yoo, Mintaek (Railroad Structure Research Team, Korea Railroad Research Institute) ;
  • Kim, Kihyun (Railroad Structure Research Team, Korea Railroad Research Institute) ;
  • Lee, Il-Wha (Railroad Structure Research Team, Korea Railroad Research Institute)
  • Received : 2019.02.26
  • Accepted : 2019.06.01
  • Published : 2019.07.31
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Abstract

In this study, a prototype abutment was constructed to establish a safety assessment technique of pier and a series of non-destructive tests using impact load. The surcharge load was loaded from 0 tonf to 2.5 tonf on the prototype abutment, and maximum surcharge load was up to 25 tonf. To analyze the behavior of the piers according to the direction of impact, a total of three types of analysis were performed: the direction of the pier, the direction perpendicular to the pier, and the outer direction of the pier. The height of the impact was also tested at each top and bottom. The measuring instrument used an accelerometer to measure the acceleration response when impacted. Based on the series of experimental results, specific values were calculated according to the direction of an impact and the surcharge load using the Fast Fourier Transform (FFT). In addition, the phase difference was used to analyze the pier from the primary 1st mode to the 4th mode.

본 연구는 교각 안전성 평가 기법을 확립하기 위해 실대형 교각을 구축하여 충격하중을 이용해 일련의 비파괴 실험을 수행하였다. 실대형 교각에 상재 하중은 0 tonf에서 2.5 tonf씩 적재하여, 최대 25 tonf 까지 적재하였다. 타격 방향에 따른 교각의 거동을 분석하기위해 교축 방향과 교축직각 방향 그리고 교각의 외측방향으로 타격하였고, 타격 높이도 교각의 상단과 하단으로 실험을 수행하였다. 계측기는 가속도계를 사용하여 타격했을 시의 가속도 응답을 측정하였다. 일련의 실험결과를 바탕으로, 고속 푸리에 변환(FFT)를 이용해 타격 방향 및 상재 하중에 따른 고유진동수를 산정했다. 또한 위상차를 이용해 교각의 1차 모드에서 4차 모드까지 분석이 가능했으며, 세굴에 대한 영향을 수치해석을 통해 분석했다. 그 결과, 2차 모드와 3차 모드를 통해 합리적인 교각의 안정성 평가가 가능한 것으로 판단된다.

Keywords

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Fig. 1. Design of prototype abutment

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Fig. 2. Prototype abutment

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Fig. 3. Mode number of abutment

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Fig. 4. Instrument equipment and impact hammer

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Fig. 5. Experiment process of prototype abutment

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Fig. 6. Schematic view of instrument position and impact direction

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Fig. 7. Time - acceleration history

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Fig. 8. Calculation of natural frequency

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Fig. 9. Calculation of phase

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Fig. 10. 1th mode of prototype abutment (Surcharge load 0 tonf)

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Fig. 11. Phase difference of prototype abutment (1th mode)

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Fig. 12. 2nd mode of prototype abutment (Surcharge load 0 tonf)

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Fig. 13. Phase difference of prototype abutment (2nd mode)

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Fig. 14. 3rd mode of prototype abutment (Surcharge load 0 tonf)

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Fig. 15. Phase difference of prototype abutment (3rd mode)

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Fig. 16. 4th mode of prototype abutment (Surcharge load 0 tonf)

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Fig. 17. Phase difference of prototype abutment (4th mode)

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Fig. 18. Numerical analysis condition of scour progression

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Fig. 19. Variation of natural frequency according to scour progression

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Fig. 20. Variation of natural frequency according to surcharge load (1th ~ 4th mode)

Table 1. Natural frequency formula

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Table 2. Eigenvalue of abutment and election of impact direction

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Table 3. Experiment case of prototype abutment

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Table 4. Comparison of natural frequency by mode number

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Table 5. Natural frequency by mode number according to scour progression

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