Title:
Effect of Bend Radius of Reinforcing Bars on Knee Joints under Closing Moments
Author(s):
Hwa-Ching Wang, Christopher S. Williams, and Gary J. Klein
Publication:
Structural Journal
Volume:
117
Issue:
5
Appears on pages(s):
315-326
Keywords:
bend radius; curved-bar node; frame corners; knee joints; strut-and- tie method
DOI:
10.14359/51725847
Date:
9/1/2020
Abstract:
An experimental program was conducted to investigate the behavior of reinforced concrete (RC) knee joints under closing moments. The geometry of knee joints creates a discontinuity region (D-region). Therefore, RC knee joints can be appropriately modeled and designed using the strut-and-tie method. At the outside of a knee joint under closing moments, a unique CTT node, known as a curved-bar node, develops. The evaluation of curved-bar nodes requires consideration of the bend radius of continuous longitudinal bars located along the outside of the joint. The experimental program described in this paper consisted of eight tests on knee joints under closing moments that were performed to study the effect of the bend radius of the longitudinal bars on the strength and behavior of the specimens and to evaluate a design equation for curved-bar nodes. An investigation into the effect of the mechanical reinforcement ratio of the longitudinal bars was also included.
Related References:
1. Swann, R. A., “Flexural Strength of Corners of Reinforced Concrete Portal Frames,” Technical Report TRA 434, Cement and Concrete Association, London, UK, 1969, 14 pp.
2. Johansson, M., “Reinforcement Detailing in Concrete Frame Corners,” ACI Structural Journal, V. 98, No. 1, Jan.-Feb. 2001, pp. 105-115.
3. Stroband, J., and Kolpa, J. J., “The Behaviour of Reinforced Concrete Column-to-Beam Joints. Part 1: Corner Joints Subjected to Negative Moments,” Report 5-83-9, Stevin Laboratory, Delft University of Technology, Delft, the Netherlands, 1983, 105 pp.
4. Hotta, H., and Nishizawa, N., “Experimental Study on Influence of Arrangement of Main Bars on Stress Transmission in Reinforced Concrete Beam-column Knee Joints,” 15th WCEE, Lisbon, Portugal, 2012, 10 pp.
5. Mayfield, B.; Kong, F. K.; and Bennison, A., “Corner Joint Details in Structural Lightweight Concrete,” ACI Journal Proceedings, V. 68, No. 5, May 1971, pp. 366-372.
6. Zouzou, A., and Haldane, D., “Detailing Reinforced Concrete Closing Corner Joints for Ductility,” Proceedings of the Institution of Civil Engineers. Structures and Buildings, V. 99, No. 1, 1993, pp. 43-48. doi: 10.1680/istbu.1993.22508
7. Marchetto, F.; Pérez Caldentey, A.; and Corres Peiretti, H., “Structural Performance of Corner Joints Subjected to a Closing Moment Using Mechanical Anchorages an Experimental Study,” Structural Concrete, V. 17, No. 6, 2016, pp. 987-1002. doi: 10.1002/suco.201500222
8. Plos, M., “Splicing of Reinforcement in Frame Corners—Experimental Studies,” Nordic Concrete Research, V. 14, No. 1, 1994, pp. 103-121.
9. Yuan, R. L.; McLelland, G. R.; and Chen, W. F., “Experiments on Closing Reinforced Concrete Corners,” Journal of the Structural Division, V. 108, No. 4, Apr. 1982, pp. 771-779.
10. Luo, Y. H.; Durrani, A. J.; Bai, S.; and Yuan, J., “Study of Reinforcing Detail of Tension Bars in Frame Corner Connections,” ACI Structural Journal, V. 91, No. 4, July-Aug. 1994, pp. 486-496.
11. Schlaich, J.; Schafer, K.; and Jennewein, M., “Toward a Consistent Design of Structural Concrete,” PCI Journal, V. 32, No. 3, 1987, pp.74-150. doi: 10.15554/pcij.05011987.74.150
12. Klein, G. J., “Curved-Bar Nodes: A Detailing Tool for Strut-and-Tie Models,” Concrete International, V. 30, No. 9, Sept. 2008, pp. 42-47.
13. ACI Committee 318, “Building Code Requirements for Structural Concrete (ACI 318-19) and Commentary (ACI 318R-19),” American Concrete Institute, Farmington Hills, MI, 2019, 624 pp.
14. Ingham, J., “Seismic Performance of Bridge Knee Joints,” PhD dissertation, University of California, San Diego, La Jolla, CA, 1995, 502 pp.
15. ASTM A615/A615M-16, “Standard Specification for Deformed and Plain Carbon-Steel Bars for Concrete Reinforcement,” ASTM International, West Conshohocken, PA, 2016, 6 pp.
16. ACI Committee 374, “Guide for Testing Reinforced Concrete Structural Elements under Slowly Applied Simulated Seismic Loads (ACI 374.2R-13),” American Concrete Institute, Farmington Hills, MI, 2013, 19 pp.