Modified Equation for Ductility Demand Based Confining Reinforcement Amount of RC Bridge Columns

철근콘크리트 교각의 소요연성도에 따른 심부구속철근량 산정식 수정

  • 이재훈 (영남대학교 건설시스템공학과) ;
  • 손혁수 ((주)서영엔지니어링 구조설계실)
  • Published : 2009.04.30


An equation for calculating confining reinforcement amount of RC bridge columns, specified in the current bridge design codes, has been made to provide additional load-carrying strength for concentrically loaded columns. The additional load-carrying strength will be equal to or slightly greater than the resistant strength of a column against axial load, which is lost because the cover concrete spalls off. The equation considers concrete compressive strength, yield strength of transverse reinforcement, and the section area ratio as major variables. Among those variables, the section area ratio between the gross section and the core section, varying by cover thickness, is a variable which considers the strength in the compression-controlled region. Therefore, the cross section ratio does not have a large effect in the aspect of ductile behavior of the tension-controlled region, which is governed by bending moment rather than axial force. However, the equation of the design codes for calculating confining reinforcement amount does not directly consider ductile behavior, which is an important factor for the seismic behavior of bridge columns. Consequently, if the size of section is relatively small or if the section area ratio becomes excessively large due to the cover thickness increased for durability, too large an amount of confining reinforcement will be required possibly deteriorating the constructability and economy. Against this backdrop, in this study, comparison and analysis were performed to understand how the cover thickness influences the equation for calculating the amount of confining reinforcement. An equation for calculating the amount of confining reinforcement was also modified for reasonable seismic design and the safety. In addition, appropriateness of the modified equation was examined based on the results of various test results performed at home and abroad.


  1. 한국도로교통협회, “도로교설계기준” 건설교통부, 2005.
  2. Park, R. and Sampson, R. A., “Ductility of Reinforced Concrete Column Sections in Seismic Design,” ACI Journal Proceedings, Vol. 69, Issue 9, Sep. 1972, pp. 543-555.
  3. Hognestad, E., A Study of Combined Bending and Axial Load in Reinforced Concrete Members, Bulletin 399, University of Illinois Engineering Experiment Station, Urbana, Ill, June 1951, 128 pp.
  4. ACI Committee 318-71, Building Code Requirements for Reinforced Concrete, American Concrete Institute, Detroit, 1971, 78 pp.
  5. ACI Committee 318, Building Code Requirements for Structural Concrete (318-05) and Commentary (318R-05), American Concrete Institute, Farmington Hills, MI, 2005.
  6. 이재훈, 배성용, 윤석구, “나선철근교각의 내진성능실험,” 대한토목학회 논문집, 21권, 1-A호, 2001, pp. 109-121.
  7. 정영수, 이재훈, 김재관 등, “고속도로 기존교량의 유형별 내진성능 평가를 위한 실험적 연구,” 한국도로공사, 2001, pp. 61-638.
  8. 이재훈, 손혁수, 고성현, 최진호, “철근콘크리트 교각의 연성요구량에 따른 내진설계,” 한국지진공학회, 2002년도 추계학술발표회, 호서대학교, 6권, 2호, 2002, pp. 316-321.
  9. 이재훈, 김익현 외 11명, “콘크리트 교각의 성능기반설계기술 개발,” 1-24과제 3차년도 보고서, 교량설계핵심기술연구단 (KBRC), 2006.
  10. 손혁수, 이재훈, “지진하중을 받는 철근콘크리트 교각의 연성도 상관관계,” 한국지진공학회논문집, 7권, 4호, 2003, pp. 51-61.
  11. 손혁수, 이재훈, “지진하중을 받는 철근콘크리트 교각의 소요연성도에 따른 심부구속철근량,” 콘크리트학회 논문집, 15권, 5호, 2003, pp. 715-725.
  12. MacGregor, J. G., Reinforced Concrete Mechanics and Design, 3rd Edition, Prentice-Hall Inc., 1997, 939 pp.
  13. 이재훈, 황정길, 최진호, “원형 철근콘크리트 교각에 대한 연성도 내진설계법의 안전성,” 콘크리트학회 논문집, 20권, 2호, 2008, pp. 193-202.
  14. 이재훈, 손혁수, 고성현, “원형 안전성 확보를 위한 철근콘크리트 교각의 연성도 내진설계,” 2004년도 워크숍, 한국지진공학회, 한전 전력연구원, 2004, pp. 312-326.

Cited by

  1. Seismic Performance of Hollow Rectangular Precast Segmental Piers vol.24, pp.6, 2012,