Title:
Shear Strength of Reinforced Concrete Columns with External Post-Tensioned Clamps
Author(s):
Julian D. Rincon, Yu-Mei Chen, Santiago Pujol, Aishwarya Y. Puranam, and Shyh-Jiann Hwang
Publication:
Structural Journal
Volume:
121
Issue:
2
Appears on pages(s):
111-125
Keywords:
external post-tensioned clamps; lateral prestress; reinforced concrete (RC) columns; retrofit; shear strength
DOI:
10.14359/51740248
Date:
3/1/2024
Abstract:
An alternative method to retrofit reinforced concrete (RC) columns
with insufficient shear reinforcement is investigated. The retrofit
involves external prestressing of the columns in the transverse
direction to increase both shear strength and drift capacity.
External post-tensioned clamps, consisting of high-strength steel
rods connecting a set of steel angles, were applied around the
columns at different spacings and initial post-tensioning stresses.
The tension induced in the steel rods exerts lateral confining pressure on the column by bearing of the angles against the corners of the column. Ten RC columns furnished with external post-tensioned clamps were tested under cyclic loads and approximately constant axial loads. In addition, six RC beams with clamps were tested under monotonically increasing loads. Both the column and beam specimens were fabricated with no transverse reinforcement in
the form of conventional steel ties. Therefore, the external clamps
were the only source of reinforcement resisting shear. The lateral
prestress provided by the clamps was observed to increase the shear
stress at the formation of the first inclined crack and at failure. As a
result, the mode of failure of columns vulnerable in shear changed
from shear failure to a more ductile failure dominated by flexure.
The observed increase in shear strength is dependent on the lateral
prestress and the tensile strength of the concrete. A simple equation,
based on the mechanics of materials, is presented to calculate
the shear strength of RC columns with external prestressing.
Related References:
1. Elwood, K. J., and Moehle, J. P., “Axial Capacity Model for Shear-Damaged Columns,” ACI Structural Journal, V. 102, No. 4, July-Aug. 2005, pp. 578-587.
2. Henkhaus, K. W., “Axial Failure of Vulnerable Reinforced Concrete Columns Damaged by Shear Reversals,” PhD dissertation, Purdue University, West Lafayette, IN, 2010.
3. Li, Y.-A.; Weng, P.-W.; and Hwang, S.-J., “Seismic Performance of Reinforced Concrete Intermediate Short Columns Failed in Shear,” ACI Structural Journal, V. 116, No. 3, May 2019, pp. 195-206. doi: 10.14359/51713309
4. Hanson, R. D., and Degenkolb, H. J., The Venezuela Earthquake, July 29, 1967, American Iron and Steel Institute, Washington, DC, 1969, 176 pp.
5. Muguruma, H.; Nishiyama, M.; and Watanabe, F., “Lessons Learned from the Kobe Earthquake—A Japanese Perspective,” PCI Journal, V. 40, No. 4, July-Aug. 1995, pp. 28-42.
6. Lew, H. S.; Leyendecker, E. V.; and Dikkers, R. D., “Engineering Aspects of the 1971 San Fernando Earthquake,” Building Science Series No. 40, National Bureau of Standards, Washington, DC, 1971, 412 pp.
7. Yurdakul, Ö.; Duran, B.; Tunaboyu, O.; and Avşar, Ö., “Field Reconnaissance on Seismic Performance of RC Buildings after the January 24, 2020 Elazığ-Sivrice Earthquake,” Natural Hazards, V. 105, No. 1, Jan. 2021, pp. 859-887. doi: 10.1007/s11069-020-04340-x
8. Milićević, I.; Marinković, M.; Blagojević, N.; and Nikolić-Brzev, S., “Performance of RC Frames in 26.11.2019. Albania Earthquake: Effects of Irregularities and Detailing,” Građevinski Materijali i Konstrukcije, V. 64, No. 3, Aug. 2021, pp. 207-213.
9. Gautam, D.; Rodrigues, H.; Bhetwal, K. K.; Neupane, P.; and Sanada, Y., “Common Structural and Construction Deficiencies of Nepalese Buildings,” Innovative Infrastructure Solutions, V. 1, No. 1, 2016, Article No. 1, 18 pp. doi: 10.1007/s41062-016-0001-3
10. Wight, J. K., and Sozen, M. A., “Shear Strength Decay in Reinforced Concrete Columns Subjected to Large Deflection Reversals,” Engineering Experiment Station, University of Illinois Urbana-Champaign, Urbana, IL, Aug. 1973, 312 pp.
11. Usta, M.; Alhmood, A.; Carrillo, J.; Cladera, A.; Laughery, L.; Pujol, S.; Puranam, A.; Rautenberg, J.; Sezen, H.; Sneed, L. H.; and To, D. V., “Shear Strength of Structural Walls Subjected to Load Cycles,” Concrete International, V. 41, No. 5, May 2019, pp. 42-48.
12. Shrestha, S.; Carrillo, J.; Sezen, H.; and Pujol, S., “Shear Strength of Shear-Controlled Columns under Cyclic Loading,” ACI Structural Journal, V. 119, No. 3, May 2022, pp. 129-140.
13. Mörsch, E., “Der Eisenbetonbau seine Theorie und Anwendung,” Konrad Wittwer GmbH & Co., Stuttgart, Germany, 1908, 376 pp. (in German)
14. Richart, F. E., “An Investigation of Web Stresses in Reinforced Concrete Beams,” Bulletin No. 166, Engineering Experiment Station, University of Illinois Urbana-Champaign, Urbana, IL, June 1927, 106 pp.
15. Vecchio, F. J., and Collins, M. P., “The Modified Compression-Field Theory for Reinforced Concrete Elements Subjected to Shear,” ACI Journal Proceedings, V. 83, No. 2, Mar.-Apr. 1986, pp. 219-231.
16. Belarbi, A.; Kuchma, D. A.; and Sanders, D. H., “Proposals for New One-Way Shear Equations for the 318 Building Code,” Concrete International, V. 39, No. 9, Sept. 2017, pp. 29-32.
17. Yamakawa, T.; Kamogawa, S.; and Kurashige, M., “Seismic Performance and Design of RC Columns Retrofitted by PC Bar Prestressing as External Hoops,” Journal of Structural and Construction Engineering (Transactions of AIJ), V. 65, No. 537, 2000, pp. 107-113.
18. Skillen, K. C., “The Effects of Transverse Reinforcement on the Strength and Deformability of Reinforced Concrete Elements,” PhD dissertation, Purdue University, West Lafayette, IN, 2020, 368 pp.
19. Olesen, S. E.; Sozen, M. A.; and Siess, C. P., “Investigation of Prestressed Reinforced Concrete for Highway Bridges: Part IV: Strength in Shear of Beams with Web Reinforcement,” Structural Research Series No. 295, Engineering Experiment Station, University of Illinois Urbana-Champaign, Urbana, IL, Aug. 1965, 162 pp.
20. Rincón, J., and Pujol, S., “Retrofit and Repair of Reinforced Concrete Columns with Active Confinement,” Proceedings of the 2023 New Zealand Society for Earthquake Engineering Annual Technical, Conference, Auckland, New Zealand, 2023, Paper No. 34, 10 pp.