KSCE Journal of Civil and Environmental Engineering Research (대한토목학회논문집)

Korean Society of Civil Engeneers (대한토목학회)
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Experimental Investigation of Aerodynamic Force Coefficients and Flutter Derivatives of Bridge Girder Sections

교량단면의 공기력계수 및 플러터계수에 관한 실험적 연구

  • 조재영 (고려대학교 사회환경시스템공학과) ;
  • 이학은 (고려대학교 사회환경시스템공학과) ;
  • 김영민 ((주)대우건설 GK설계팀)
  • Received : 2006.06.14
  • Accepted : 2006.08.25
  • Published : 2006.09.30
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Abstract

The aim of this study is to investigate a correlation between fundamental data on aerodynamic characteristics of bridge girder cross-sections, such as aerodynamic force coefficients and flutter derivatives, and their aerodynamic behaviour. The section model tests were carried out in three stages. In the first stage, seven deck configurations were studied, namely; Six 2-edge girders and one box girder. In this stage, changes in aerodynamic force coefficients due to geometrical shape of girders, incidence angle of flow, wind directions and turbulence intensities were studied by static section model tests. In the second stage, the dynamic section model tests were carried out to investigate the relativity of static coefficients to dynamic responses. And finally, the two-dimensional (lift-torsion) aerodynamic derivatives of three bridge deck configurations were investigated by dynamic section model tests. The aerodynamic derivatives can be best described as a representation of the aerodynamic damping and the aerodynamic stiffness provided by the wind for a given deck geometry. The method employed here to extract these unsteady aerodynamic properties is known as the initial displacement technique. It involves the measurement of the decay in amplitude with time of an initial displacement of the deck in heave and torsion, for various wind speeds, in smooth flow. It is suggested that the proposed aerodynamic force coefficients and flutter derivatives of bridge girder sections will be potentially useful for the aeroelastic analysis and buffeting analysis.

본 연구의 목적은 교량 거더 단면의 공기역학적 특성을 나타내는 기본 자료인 공기력계수와 플러터계수가 동적응답과 어떠한 상관관계를 가지는지를 규명하는데 있다. 이를 위해 세 단계의 단면모형실험이 수행되었다. 첫 번째 단계에서는 총 7개의 거더 단면 즉, 6개의 플레이트거더 단면과 1개의 박스거더 단면이 고려되었으며 거더 단면의 기하학적 형상, 영각, 바람의 방향 그리고 기류조건이 공기력계수인 항력계수, 양력계수 그리고 모멘트계수에 미치는 영향을 정적 단면모형실험을 통해 살펴보았다. 두 번째 단계에서는 동적실험을 통해 각 단면의 공기력계수와 동적응답의 상관성을 검증하였다. 마지막으로 2자유도하의 동적 단면모형실험을 통해 세 개의 거더 단면의 플러터계수를 산출하고 이를 동적실험결과와 비교하였다. 주어진 단면형상에 대한 비정상 공기력에 의해 변화되는 시스템의 감쇠와 강성을 가장 잘 반영하는 플러터계수는 초기변위-자유진동시스템을 이용하여 추출하였다. 이를 위해 등류조건에서 풍속별로 교량단면의 수직 및 비틀림 초기변위의 시간에 따른 진폭의 감쇠를 측정하였다. 본 연구에서 제시한 교량단면의 공기력계수와 플러터계수는 공탄석해석 및 버펫팅해석을 위한 기본 자료로 유용하게 쓰일 것으로 보인다.

Keywords

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