A Study on the Flexural Minimum Reinforcement for Prevention of Brittle Failure Specified in KCI and EN Codes

유럽과 국내기준에 규정된 취성파괴 방지를 위한 휨 최소철근량 고찰

  • Received : 2013.12.09
  • Accepted : 2014.03.28
  • Published : 2014.04.30


In the design of reinforced rectangular concrete beam structure, the minimum amount of flexural reinforcement is required to avoid brittle failure. KCI code is based on concept of ultimate strength and usually used as a model code. But bridge design code enacted by Ministry of land, transportation and maritime affairs in 2012 is based on concept of limit state and similar to Euro code EN 1992-2. This means that the minimum reinforcement presented in both design codes has different origination and safety margin. When rectangular concrete beams with minimum reinforcement are designed according to EN and KCI codes, the amount of minimum reinforcement specified in EN code is only 76% of that in KCI code. This makes the design engineers to be confused. In this study, flexural tests were conducted on nine beams with the two different minimum reinforcement specified in KCI and EN design codes. In results, the measured ratios of nominal strength to crack strength from the test were about 25% greater than those evaluated from the equations presented in KCI and EN codes. The EN beams having only 76% of the minimum reinforcement for the KCI beams were fractured by rupture of steel reinforcement but in ductile manner. It is confirmed that the minimum reinforcement concrete beams designed according to both codes have enough safety margin in flexural capacity and moreover in ductility.


Supported by : 한국건설교통기술평가원


  1. Subramanian, N., "Limiting Reinforcement Ratios for RC Flexural Members," The Indian Concrete Journal, Vol. 84, No. 9, 2010, pp. 71-80.
  2. Stephen J, S., Richard, B., and Bijan, K. "Making Sense of Minimum Flexural Reinforcement Requirements for Reinforced Concrete Members," PCI Journal, Vol. 55, Issue 3, 2010, pp. 64-85.
  3. Yoo, S. W. and Her, Y., "A Proposal of Minimum Steel Ratio Considering Size Effect for Flexural Reinforced Concrete Member," Journal of the Korean Society of Safety, Vol. 25, No. 6, 2010, pp. 128-136.
  4. Bruckner, M. and Eligenhausen, R., "Minimum Reinforcement in RC Beams," 2nd International PhD Symposium in Civil Engineering, Budapest, 1998, pp. 1-7.
  5. Ahn, Y. S., "An Experimental Study of Flexure of Reinforced Concrete for Minimum Steel Ratio Considering Size Effect," Doctoral Thesis, Woosuk University, 2010, 47 pp.
  6. Bosco, C., Carpinteri, A., and Debernardi, P. G., "Minimum Reinforcement in High-Strength Concrete," Journal of Structural Engineering, Vol. 116, No. 2, 1990, pp. 427-437.
  7. Korea Concrete Institute, Concrete Design Code and Commentary, Kimoondang Publishing Company, Seoul, Korea, 2012, pp. 116-119.
  8. Hendy, C. R. and Smith, D. A., Designer's Guide to EN 1992-2 Eurocode 2: Design of Concrete Structures, Part 2: Concrete Bridges, Thomas Telford, Eurocodes Expert, 2007, pp. 276-277.
  9. Kwon, S. B. and Yoon, Y. S., "Flexural Behavior of RC Beams Using High-Strength Reinforcement for Ductility Assessment," Journal of KOSHAM, Vol. 2, No. 1, 2002, pp. 119-126.
  10. Shin, S. W., Kang, H., Ahn, J, M., and Kim, D. W., "Flexural Capacity of Singly Reinforced Beam with 150 MPa Ultra High-Strength Concrete," Indian Journal of Engineering & Materials Sciences, Vol. 17, No. 6, 2010, pp. 414-426.
  11. Rachid, M. A. and Mansur, M. A., "Reinforced Hing-Strength Concrete Beams in Flexure," ACI Structural Journal, Vol. 102, No. 3, 2005, pp. 462-471.
  12. Shin, S. W., Yoo, S. H., An, J. M., and Lee, K. S., "Flexural Design and Ductile Capacity of Reinforced High Strength Concrete Beams," Journal of Korea Concrete Institute, Vol. 8, No. 6, 1996, pp. 141-149.
  13. Hong, G. H., "Flexural Performance Evaluation of Reinforced Concrete Beams with High-Strength Concrete and Reinforcing Bars," Journal of Architectural Institute of Korea, Vol. 27, No. 6, 2011, pp. 49-56.