Title:
Anchorage Strength of Closely Spaced Hooked Bars
Author(s):
Ali Ajaam, Samir Yasso, David Darwin, Matthew O’Reilly, and Jayne Sperry
Publication:
Structural Journal
Volume:
115
Issue:
4
Appears on pages(s):
1143-1152
Keywords:
anchorage; beam-column joints; high-strength concrete; highstrength steel; hooks; reinforced concrete; reinforcement; spacing; staggered hooks
DOI:
10.14359/51702065
Date:
7/1/2018
Abstract:
The effect of close spacing on the anchorage strength of standard hooks is investigated. Sixty-seven simulated beam-column joint specimens were tested, each containing three, four, or six No. 5, 8, or 11 (No. 16, 25, or 36) hooked bars arranged in one or two layers with center-to-center spacing ranging from two to six bar diameters. Anchorage strengths are compared with those of specimens containing two hooked bars with spacings of six to 12 bar diameters. The results demonstrate that the provisions in ACI 318-14 tend to overestimate the anchorage strength of hooked bars as concrete compressive strength and bar size increase and as spacing between bars decreases. Decreasing center-to-center spacing below six bar diameters results in lower anchorage strengths than for hooked bars with wider spacing. The anchorage strength of hooked bars can be represented by considering the minimum of the horizontal and vertical spacing between bars.
Related References:
ACI Committee 318, 2014, “Building Code Requirements for Structural Concrete (ACI 318-14) and Commentary (ACI 318R-14),” American Concrete Institute, Farmington Hills, MI, 520 pp.
Ajaam, A.; Darwin, D.; and O’Reilly, M., 2017, “Anchorage Strength of Reinforcing Bars with Standard Hooks,” SM Report No. 125, University of Kansas Center for Research, Lawrence, KS, 365 pp.
ASTM C1017/C1017M-13, 2013, “Standard Specification for Chemical Admixtures for Use in Producing Flowing Concrete,” ASTM International, West Conshohocken, PA, 9 pp.
ASTM A1035/A1035-14, 2014, “Standard Specification for Deformed and Plain Low-Carbon, Chromium, Steel Bars for Concrete Reinforcement,” ASTM International, West Conshohocken, PA, 7 pp.
ASTM C31/C31M-15ε1, 2015, “Standard Practice for Making and Curing Concrete Test Specimens in the Field,” ASTM International, West Conshohocken, PA, 6 pp.
ASTM C494/C494M-13, 2013, “Standard Specification for Chemical Admixtures for Concrete,” ASTM International, West Conshohocken, PA, 2013, 10 pp.
ASTM A615/A615M-15, 2015, “Standard Specification for Deformed and Plain Carbon-Steel Bars for Concrete Reinforcement,” ASTM International, West Conshohocken, PA, 8 pp.
Draper, N. R., and Smith, H., 1981, Applied Regression Analysis, second edition, Wiley, New York, 709 pp.
Hamad, B. S.; Jirsa, J. O.; and de Paolo, N. I., 1993, “Anchorage Strength of Epoxy-Coated Hooked Bars,” ACI Structural Journal, V. 90, No. 2, Mar.-Apr., pp. 210-217.
Lee, J., and Park, H., 2010, “Bending – Applicability Study of Ultra-Bar (SD 600) and Ultra-Bar for Rebar Stirrups and Ties (SD 500 and 600) for Compression Rebar,” Korea Concrete Institute, Aug., 504 pp. (translated from Korean)
Marques, J. L. G., and Jirsa, J. O., 1975, “A Study of Hooked Bar Anchorages in Beam-Column Joints,” ACI Journal Proceedings, V. 72, No. 5, May, pp. 198-209.
Peckover, J., and Darwin, D., 2013, “Anchorage of High-Strength Reinforcing Bars with Standard Hooks: Initial Tests,” SL Report No. 13-1, University of Kansas Center for Research, Lawrence, KS, 47 pp.
Pinc, R. L.; Watkins, M. D.; and Jirsa, J. O., 1977, “Strength of Hooked Bar Anchorages in Beam-Column Joints,” Report 77-3, University of Texas at Austin, Austin, TX, 67 pp.
Ramirez, J. A., and Russell, B. W., 2008, “Transfer, Development, and Splice Length for Strand/Reinforcement in High-Strength Concrete,” Transportation Research Board, National Research Council, Washington, DC, pp. 99-120.
Searle, N.; DeRubeis, M.; Darwin, D.; Matamoros, A.; O’Reilly, M.; and Feldman, L., 2014, “Anchorage of High-Strength Reinforcing Bars with Standard Hooks – Initial Tests,” SM Report No. 108, University of Kansas Center for Research, Lawrence, KS, 120 pp.
Sperry, J.; Al-Yasso, S.; Searle, N.; DeRubeis, M.; Darwin, D.; O’Reilly, M.; Matamoros, A.; Feldman, L.; Lepage, A.; Lequesne, R.; and Ajaam, A., 2015a, “Anchorage of High-Strength Reinforcing Bars with Standard Hooks,” SM Report No. 111, University of Kansas Center for Research, Lawrence, KS, 260 pp.
Sperry, J.; Darwin, D.; O’Reilly, M.; and Lequesne, R., 2015b, “Anchorage Strength of Conventional and High-Strength Hooked Bars in Concrete,” SM Report No. 115, University of Kansas Center for Research, Lawrence, KS, 281 pp.
Sperry, J.; Yasso, S.; Searle, N.; DeRubeis, M.; Darwin, D.; O’Reilly, M.; Matamoros, A.; Feldman, L.; Lepage, A.; Lequesne, R.; and Ajaam, A., 2017a, “Conventional and High-Strength Hooked Bars—Part 1: Anchorage Tests,” ACI Structural Journal, V. 114, No. 1, Jan.-Feb., pp. 255-266.
Sperry, J.; Darwin, D.; O’Reilly, M.; Lequesne, R.; Yasso, S.; Matamoros, A.; Feldman, L.; and Lepage, A., 2017b, “Conventional and High-Strength Hooked Bars—Part 2: Data Analysis,” ACI Structural Journal, V. 114, No. 1, Jan.-Feb., pp. 267-276. doi: 10.14359/51689457
Sperry, J.; Darwin, D.; O’Reilly, M.; Lepage, A.; Lequesne, R.; Matamoros, A.; Feldman, L.; Yasso, S.; Searle, N.; DeRubeis, M.; and Ajaam, A., 2018, “Conventional and High-Strength Steel Hooked Bars: Detailing Effects,” ACI Structural Journal, V. 115, No. 1, Jan., pp. 255-265. doi: 10.14359/51700920
Yasso, S.; Darwin, D.; and O’Reilly, M., 2017, “Anchorage Strength of Standard Hooked Bars in Simulated Exterior Beam-Column Joints,” SM Report No. 124, University of Kansas Center for Research, Lawrence, KS, 330 pp.