Title:
Confinement Reinforcement of Cyclically Loaded Normal-Strength Concrete Tied Columns under High Axial Loads
Author(s):
Wen-Cheng Shen and Shyh-Jiann Hwang
Publication:
Structural Journal
Volume:
123
Issue:
3
Appears on pages(s):
165-178
Keywords:
column; confining reinforcement; crosstie configuration; high axial load; ultimate drift ratio
DOI:
10.14359/51749406
Date:
5/1/2026
Abstract:
In high-rise buildings, lower-story columns must withstand significant seismic shear forces while maintaining sufficient deformation capacity. This capacity is provided through effective confinement using transverse reinforcement. ACI CODE-318-25 specifies that confining reinforcement should be proportional to the applied axial load when the axial load exceeds 0.3Agfc′ and requires all longitudinal bars to be laterally supported with seismic hooks. However, the implementation of seismic hooks at both ends of crossties brings challenges for on-site reinforcement assembly.
This study experimentally investigates full-scale reinforced concrete (RC) column specimens subjected to quasi-static cyclic loading while under a constant high axial load. The objectives are to validate the ACI CODE-318-25 confinement requirements and to evaluate the feasibility of relaxing seismic hook requirements. The results confirm that columns designed in accordance with ACI CODE-318-25 satisfy the required 3% deformation capacity. Furthermore, satisfactory seismic performance can be achieved with crossties incorporating alternating 135-degree and 90-degree hooks, although at the expense of increased confining reinforcement.
Related References:
1. ACI Committee 318, “Building Code Requirements for Structural Concrete (ACI 318-11) and Commentary (ACI 318R-11),” American Concrete Institute, Farmington Hills, MI, 2011, 503 pp.
2. Park, R., “Ductile Design Approach for Reinforced Concrete Frames,” Earthquake Spectra, V. 2, No. 3, 1986, pp. 565-619. doi: 10.1193/1.1585398
3. NZS 3101.1&2:2006, “Concrete Structures Standard,” Standards New Zealand, Wellington, New Zealand, 2006, 754 pp.
4. Watson, S.; Zahn, F. A.; and Park, R., “Confining Reinforcement for Concrete Columns,” Journal of Structural Engineering, ASCE, V. 120, No. 6, 1994, pp. 1798-1824. doi: 10.1061/(ASCE)0733-9445(1994)120:6(1798)
5. Paultre, P., and Légeron, F., “Confinement Reinforcement Design for Reinforced Concrete Columns,” Journal of Structural Engineering, ASCE, V. 134, No. 5, 2008, pp. 738-749. doi: 10.1061/(ASCE)0733-9445(2008)134:5(738)
6. CAN/CSA-A23.3-04 (R2010), “Design of Concrete Structures,” CSA Group, Toronto, ON, Canada, 2004, 214 pp.
7. Elwood, K. J.; Maffei, J.; Riederer, K. A.; and Telleen, K., “Improving Column Confinement - Part 1: Assessment of Design Provisions,” Concrete International, V. 31, No. 11, Nov. 2009, pp. 32-39.
8. Berry, M.; Parrish, M.; and Eberhard, M. O., “PEER Structural Performance Database User’s Manual (Version 1.0),” Pacific Earthquake Engineering Research Center, University of California, Berkeley, Berkeley, CA, 2004, 43 pp.
9. Elwood, K. J.; Maffei, J.; Riederer, K. A.; and Telleen, K., “Improving Column Confinement - Part 2: Proposed New Provisions for the ACI 318 Building Code,” Concrete International, V. 31, No. 12, Dec. 2009, pp. 41-48.
10. ACI Committee 318, “Building Code Requirements for Structural Concrete (ACI 318-14) and Commentary (ACI 318R-14),” American Concrete Institute, Farmington Hills, MI, 2014, 520 pp.
11. ACI Committee 318, “Building Code Requirements for Structural Concrete (ACI 318-19) and Commentary (ACI 318R-19) (Reapproved 2022),” American Concrete Institute, Farmington Hills, MI, 2019, 624 pp.
12. ACI Committee 318, “Building Code for Structural Concrete—Code Requirements and Commentary (ACI CODE-318-25),” American Concrete Institute, Farmington Hills, MI, 2025, 702 pp.
13. Shen, W. C., and Hwang, S. J., “Confinement Reinforcement of High-Strength Reinforced Concrete Tied Columns under High Axial Load,” ACI Structural Journal, V. 120, No. 3, May 2023, pp. 145-155.
14. Ousalem, H.; Kabeyasawa, T.; Tasai, A.; and Ohsugi, Y., “Experimental Study on Seismic Behavior of Reinforced Concrete Columns under Constant and Variable Axial Loadings,” Proceedings of the Japan Concrete Institute, V. 24, No. 2, 2002, pp. 229-234.
15. Vu, N. S.; Li, B.; and Tran, C. T. N., “Seismic Behavior of Reinforced Concrete Short Columns Subjected to Varying Axial Load,” ACI Structural Journal, V. 119, No. 6, Nov. 2022, pp. 99-112.
16. Zimos, D. K.; Papanikolaou, V. K.; and Kappos, A. J., “Shear-Critical Reinforced Concrete Columns under Increasing Axial Load,” ACI Structural Journal, V. 117, No. 5, Sept. 2020, pp. 29-39.
17. Tsai, W. T., “Design of Seismic Confinement of RC Tied Columns,” master’s thesis, Department of Civil Engineering, National Taiwan University, Taipei, Taiwan, 2016, 276 pp. (in Chinese)
18. ACI Committee 374, “Acceptance Criteria for Moment Frames Based on Structural Testing and Commentary (ACI 374.1-05) (Reapproved 2019),” American Concrete Institute, Farmington Hills, MI, 2005, 9 pp.
19. ASCE/SEI 41-17, “Seismic Evaluation and Retrofit of Existing Buildings,” American Society of Civil Engineers, Reston, VA, 2017, 576 pp.
20. ASCE/SEI 41-23, “Seismic Evaluation and Retrofit of Existing Buildings,” American Society of Civil Engineers, Reston, VA, 2023, 567 pp.
21. MacRae, G. A., “P-Δ Effects on Single-Degree-of-Freedom Structures in Earthquakes,” Earthquake Spectra, V. 10, No. 3, 1994, pp. 539-568. doi: 10.1193/1.1585788
22. ASCE/SEI 7-22, “Minimum Design Loads for Buildings and Other Structures,” American Society of Civil Engineers, Reston, VA, 2022, 975 pp.