Title:
Flexural Behavior of Reinforced Concrete Columns with Supplementary V-Shaped Ties
Author(s):
Keun-Hyeok Yang, Min-Kyoung Kwak, and Jae-Il Sim
Publication:
Structural Journal
Volume:
114
Issue:
5
Appears on pages(s):
1177-1188
Keywords:
columns; crossties; flexural ductility; V-ties
DOI:
10.14359/51700781
Date:
9/1/2017
Abstract:
This study examined the flexural behavior of reinforced concrete (RC) columns with V-shaped ties as an alternative to the conventional crossties specified in ACI 318-14. Ten columns were tested to failure under constant axial loads and reversed cyclic lateral loads with the aim of exploring the potential for practical application of the proposed V-tie arrangement for enhancing column ductility. The parameters investigated were the axial load level, the compressive strength of concrete, and the column section size. The backbone curves of columns obtained from the reversed lateral load-displacement relationship were compared with predictions derived using a nonlinear two-dimensional (2-D) lamina method. Test results ascertained that the conventional crossties with a 90-degree hook are unfavorable to the enhancement of the flexural ductility of columns and prevention of the premature buckling of longitudinal bars, particularly under high axial load levels, owing to the opening of their 90-degree hooks. Meanwhile, the extraction of V-tie legs from the core concrete was not observed until the columns failed. As a result, higher displacement ductility ratio and work damage indicator were obtained for V-tie columns than for crosstie columns, indicating that the superiority of the V-ties to the conventional crossties in enhancing the flexural ductility of columns becomes more pronounced as the axial load level and concrete compressive strength increase. The flexural behavior of RC columns with V-ties could be accurately evaluated using the proposed 2-D lamina approach. However, the slope at the descending branch of the lateral load-displacement curve of the crosstie columns was lower than the corresponding prediction results owing to the opening of the 90-degree hooks.
Related References:
1. Joint ACI-ASCE Committee 441, “High-Strength Concrete Columns: State of the Art (ACI 441R-96),” ACI Structural Journal, V. 94, No. 5, Sept.-Oct. 1997, pp. 323-335.
2. Ozcebe, G., and Saatcioglu, M., “Confinement of Concrete Columns for Seismic Loading,” ACI Structural Journal, V. 84, No. 4, July-Aug. 1987, pp. 308-315.
3. Sheikh, S. A., and Khoury, S. S., “Confined Columns with Stubs,” ACI Structural Journal, V. 90, No. 4, July-Aug. 1993, pp. 414-431.
4. Sheikh, S. A., and Uzumeri, S. M., “Analytical Model for Concrete Confinement in Tied Columns,” Journal of Structural Engineering, ASCE, V. 108, 1982, pp. 2703-2722.
5. ACI Committee 318, “Building Code Requirements for Structural Concrete (ACI 318-14) and Commentary (ACI 318R-14),” American Concrete Institute, Farmington Hills, MI, 2014, 519 pp.
6. Fafitis, A., and Shah, S. P., “Predictions of Ultimate Behavior of Confined Columns Subjected to Large Deformations,” ACI Structural Journal, V. 82, No. 4, July-Aug. 1985, pp. 423-433.
7. Mander, J. B.; Priestley, M. J. N.; and Park, R., “Observed Stress-Strain Behavior of Confined Concrete,” Journal of Structural Engineering, ASCE, V. 114, No. 8, 1988, pp. 1827-1849.
8. Saatcioglu, M., and Razvi, S. R., “Strength and Ductility of Confined Concrete,” Journal of Structural Engineering, ASCE, V. 118, No. 6, 1992, pp. 1590-1607.
9. Lukkunaprasit, P., and Sittipunt, C., “Ductility Enhancement of Moderately Confined Concrete Tied Columns with Hook-Clips,” ACI Structural Journal, V. 100, No. 4, July-Aug. 2003, pp. 422-429.
10. Azizinamini, A.; Kuska, S. S. B.; Brungardt, P.; and Hatfield, E., “Seismic Behavior of Square High-Strength Concrete Columns,” ACI Structural Journal, V. 91, No. 3, May-June 1994, pp. 336-345.
11. Yang, K. H., and Kim, W. W., “Axial Compression Performance of Reinforced Concrete Short Columns with Supplementary V-Shaped Ties,” ACI Structural Journal, V. 113, No. 6, Nov.-Dec. 2016, pp. 1347-1356.
12. Bae, S., “Seismic Performance of Full-Scale Reinforced Concrete Columns,” PhD dissertation, University of Texas at Austin, Austin, TX, 2005, 312 pp.
13. Kim, W. W.; Mun, J. H.; and Yang, K. H., “Simplified Model for the Stress-Strain Relationship of Confined Concrete,” Journal of the Architectural Institute of Korea: Structure & Construction, V. 31, No. 4, 2015, pp. 79-86. (in Korean)
14. Yang, K. H., and Kang, T. H.-K., “Equivalent-Strain Distribution Factor for Unbonded Tendon Stress at Ultimate,” ACI Structural Journal, V. 108, No. 2, Mar.-Apr. 2011, pp. 217-226.
15. Federal Emergency Management Agency, “Prestandard and Commentary for the Seismic Rehabilitation of Buildings,” FEMA 356, Washington, DC, 2000, 518 pp.
16. Yang, K. H.; Mun, J. H.; Cho, M. S.; and Kang, T. H. K., “A Stress-Strain Model for Various Unconfined Concrete in Compression,” ACI Structural Journal, V. 111, No. 4, July-Aug. 2014, pp. 819-826.
17. Kim, W. W.; Mun, J. H.; and Yang, K. H., “Simplified Model for the Stress-Strain Relationship of Confined Concrete,” Journal of the Architectural Institute of Korea: Structure & Construction, V. 31, No. 4, 2015, pp. 79-86. (in Korean)