International Journal of Concrete Structures and Materials

Korea Concrete Institute (한국콘크리트학회)
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Effective Length of Reinforced Concrete Columns in Braced Frames

  • Tikka, Timo K. (Stantec Consulting) ;
  • Mirza, S. Ali (Civil Engineering, Lakehead University)
  • Received : 2013.03.31
  • Accepted : 2014.01.14
  • Published : 2014.06.30
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Abstract

The American Concrete Institute (ACI) 318-11 permits the use of the moment magnifier method for computing the design ultimate strength of slender reinforced concrete columns that are part of braced frames. This computed strength is influenced by the column effective length factor K, the equivalent uniform bending moment diagram factor $C_m$ and the effective flexural stiffness EI among other factors. For this study, 2,960 simple braced frames subjected to short-term loads were simulated to investigate the effect of using different methods of calculating the effective length factor K when computing the strength of columns in these frames. The theoretically computed column ultimate strengths were compared to the ultimate strengths of the same columns computed from the ACI moment magnifier method using different combinations of equations for K and EI. This study shows that for computing the column ultimate strength, the current practice of using the Jackson-Moreland Alignment Chart is the most accurate method for determining the effective length factor. The study also shows that for computing the column ultimate strength, the accuracy of the moment magnifier method can be further improved by replacing the current ACI equation for EI with a nonlinear equation for EI that includes variables affecting the column stiffness and proposed in an earlier investigation.

Keywords

References

  1. ACI Committee 318. (2005). Building code requirements for structural concrete (ACI 318-05) and commentary (ACI 318R-05). Farmington Hills, MI: American Concrete Institute.
  2. ACI Committee 318. (2011). Building code requirements for structural concrete (ACI 318-11) and commentary. Farmington Hills, MI: American Concrete Institute.
  3. Bazant, Z. P., & Oh, B. H. (1984). Deformation of progressively cracking reinforced concrete beams. ACI Journal, 81(3), 268-278.
  4. Blomeier, G. A., & Breen, J. E. (1975). Effect of yielding of restraints on slender concrete columns with sidesway prevented. In Reinforced concrete columns, SP-50 (pp. 41-65). Detroit, MI: American Concrete Institute.
  5. Breen, J. E., & Ferguson, P. M. (1964). The restrained long concrete column as a part of a rectangular frame. ACI Journal, 61(5), 563-587.
  6. CAC. (2006). Explanatory notes on CSA standard A23.3-04. Concrete design handbook (3rd ed.) (pp. 217-358). Ottawa, ON: Cement Association of Canada.
  7. Chen, W. F., & Lui, E. M. (1987). Structural stability-Theory and implementation. New York, NY: Elsevier Science Publishing Company Inc.
  8. Cranston, W. B. (1972). Analysis and design of reinforced concrete columns. Research Report No. 20, Paper 41.020, Cement and Concrete Association, London, England.
  9. CSA. (2004). Design of concrete structures-CSA standard A23.3-04. Mississauga, ON: Canadian Standard Association.
  10. Duan, L., King, W. S., & Chen, W. F. (1993). K-factor equation to alignment charts for column design. ACI Structural Journal, 90(3), 242-248.
  11. Ford, J. S., Chang, D. C., & Breen, J. E. (1981a). Experimental and analytical modeling of unbraced multipanel concrete frames. ACI Journal, 78(1), 21-35.
  12. Ford, J. S., Chang, D. C., & Breen, J. E. (1981b). Behavior of unbraced multipanel concrete frames. ACI Journal, 78(2), 97-115.
  13. Ford, J. S., Chang, D. C., & Breen, J. E. (1981c). Design indications from tests of unbraced multipanel concrete frames. Concrete International, 3(3), 37-47.
  14. Furlong, R. W., & Ferguson, P. M. (1966). Test of frames with columns in single curvature. In Symposium on reinforced concrete columns, SP-13 (pp. 55-73). Detroit, MI: American Concrete Institute.
  15. Mirza, S. A. (1990). Flexural stiffness of rectangular reinforced concrete columns. ACI Structural Journal, 87(4), 425-435.
  16. Mirza, S. A., & MacGregor, J. G. (1989). Slenderness and strength reliability of reinforced concrete columns. ACI Structural Journal, 86(4), 428-438.
  17. Park, R., Priestly, M. J. N., & Gill, W. D. (1982). Ductility of square-confined concrete columns. Journal of the Structural Division, ASCE, 108(ST4), 929-950.
  18. Tikka, T. K., & Mirza, S. A. (2002). Examination of secondorder effects in structural concrete columns and braced frames. Civil Engineering Research Series Report No. CE- 02-2, Lakehead University, Thunder Bay, ONtario, Canada.
  19. Tikka, T. K., & Mirza, S. A. (2004). Equivalent uniform moment diagram factor for reinforced concrete columns. ACI Structural Journal, 101(4), 521-531.
  20. Tikka, T. K., & Mirza, S. A. (2005). Nonlinear EI equation for slender reinforced concrete columns. ACI Structural Journal, 102(6), 839-848.
  21. Yalcin, C., & Saatcioglu, M. (2000). Inelastic analysis of reinforced concrete columns. Computers & Structures, 77(5), 539-555. https://doi.org/10.1016/S0045-7949(99)00228-X

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