A Study on the Moment Capacity of H-Section Flexural Members with Local Buckling

국부좌굴이 발생하는 H-형강 휨부재의 강도에 관한 연구

  • 서건호 (영남대학교 건설환경공학과) ;
  • 서상정 (영남대학교 건설환경공학과) ;
  • 권영봉 (영남대학교 건설환경공학과)
  • Received : 2011.06.07
  • Accepted : 2011.11.30
  • Published : 2011.12.27

Abstract

This paper describes the moment capacity of flexural members with local buckling based on a series of FE and experiment results. Thin-walled flexural members undergo local, lateral-torsional, or interactive buckling according to the section geometries and lateral boundary conditions. Flexural members with large width-to-thickness ratios in the flanges or the web may undergo local buckling before lateral-torsional buckling. Local buckling has a negative effect on the flexural strength based on the lateral-torsional buckling of flexural members. This phenomenon should be considered in the estimation of the flexural strength of thin-walled sections. Flexural members with various width-to-thickness ratios in their flanges and web were analyzed. Initial imperfections in the local buckling mode, and residual stresses, were included in the FE analyses. Simple bending moment formulae for flexural members were proposed based on the FE and test results to account for local and lateral-torsional buckling. The proposed bending moment formulae for the thin-walled flexural members in the Direct Strength Method use the empirical strength formula and the grosssection modulus. The ultimate flexural strengths predicted by the proposed moment formulae were compared with the AISC (2005), Eurocode3 (2003), and Korean Highway Bridge Design Specifications (2010). The comparison showed that the proposed bending moment formulae can reasonably predict the ultimate moment capacity of thin-walled flexural members.

본 논문에는 국부좌굴이 발생하는 휨부재의 유한요소해석 및 실험에 근거한 단면의 휨강도에 대하여 기술하였다. 박판으로 구성된 휨부재는 단면조건 및 횡방향 경계조건에 따라서 국부좌굴, 횡-비틀림좌굴 및 두 좌굴의 혼합좌굴이 발생하게 된다. 플랜지나 복부의 폭-두 께비가 큰 경우 횡-비틀림좌굴 발생 이전에 국부좌굴이 발생하며, 국부좌굴은 휨부재의 횡-비틀림좌굴강도에 영향을 미치게 된다. 이런 현상은 박판 형강의 휨강도 산정 시 고려하여야 한다. 다양한 폭-두께비를 갖는 플랜지와 복부판으로 구성된 휨부재의 해석에 국부좌굴 및 횡좌굴 모드의 초기처짐 및 잔류응력을 포함하였다. 해석결과 및 실험에 근거하여 국부좌굴과 횡-비틀림좌굴을 고려하는 설계강도식을 제안하였다. 제안된 직접강도법은 실험에 근거한 강도식과 유효단면 대신 총단면의 단면계수를 사용한다. 제안된 강도식에 의한 휨강도를 AISC, EC3 및 도로교설계기준과 비교하여 보았다. 제안된 직접강도법은 국부좌굴과 횡-비틀림좌굴의 혼합 유무와 상관없이 휨부재의 휨강도를 적절하게 예측할 수 있는 것으로 판단되었다.

Acknowledgement

Supported by : 한국연구재단

References

  1. 강두원, 권영봉(2009) 원형강관 기둥의 강도에 관한 연구, 한국강구조학회, 한국강구조학회논문집, 제21권, 제5호, pp.505-514.
  2. 국토해양부(2010) 도로교설계기준.
  3. 권영봉(2000) Buckling Analysis Program(BAP) 사용자 메뉴얼, 영남대학교.
  4. 서건호, 권영봉(2011) H-형강 휨부재의 실험 보고서, 영남대학교 방재연구소.
  5. AASHTO (2007) LRFD Bridge Design Specifications, American Association of State Highway Transportation Officials, Washington, DC, USA.
  6. AISC (1986) LRFD Specification for Structural Steel Buildings, American Institute of Steel Construction, Washington, DC, USA.
  7. AISC (2005) Specification for Structural Steel Buildings, American Institute of Steel Construction, Washington, DC, USA.
  8. AISI (2004) North American Specifications for the Design of Cold-Formed Steel Structural Members, American Iron and Steel Institute, Supplement No. 1. Washington, DC, USA.
  9. Basler, K. (1963) Strength of Plate Girders in Bending, Trans. ASCE, Vol. 128, Part II, pp.655-686.
  10. Bryan, G.H. (1891) On the Stability of a Plane Plate under Thrusts in Its Own Plane with Application to Buckling of the Sides of a Ship, Proc., London Math. Vol. 22.
  11. European Committee for Standardisation (2003) Eurocode 3-Part 1.1: Design of Steel Structures-General rules and rules for buildings, Brussels, Belgium.
  12. European Committee for Standardisation (2006) Eurocode 3-Part 1.5 : Design of Steel Structures-Plated steel elements, Brussels, Belgium.
  13. Hancock, G.J., Murray T.M., and Ellifritt D.S. (2004) Cold-Formed Steel Structures to the AISI Specification, Marcel Dekker Inc.
  14. FEA Co., Ltd. (2009) Lusas Element Reference Manual & User's Manual (version 14.3-1).
  15. Kemp, A.R. (1996) Inelastic lateral and local buckling in design codes, Journal of Structural Engineering, ASCE, Vol. 122, No. 4, pp.374-482. https://doi.org/10.1061/(ASCE)0733-9445(1996)122:4(374)
  16. Kwon, Y.B., Kim, N.G., and Hancock, G.J. (2007) Compression tests of welded section columns undergoing buckling interaction, Journal of Constructional Steel Research, Vol. 63, pp.1590-1602. https://doi.org/10.1016/j.jcsr.2007.01.011
  17. Schafer, B.W. and Pekoz, T. (2003) Direct Strength Prediction of Cold‐Formed Steel Members using Numerical Elastic Buckling Solutions, Thin‐Walled Structures, Elsevier.
  18. Standards Australia (2005) Cold‐Formed Steel Structures AS/NZS 4600, Sydney, Australia.
  19. Topkaya, C. and Sahin, S. (2011) A Comparative study of AISC and EC3 strength limit states, International. Journal of Steel Structures, Vol. 11, No.1, pp.13-27. https://doi.org/10.1007/S13296-011-1002-x