Title:
Lap Splicing of Large Steel Reinforcing Bars
Author(s):
Ryan Rulon, Rémy D. Lequesne, David Darwin, and Andrés Lepage
Publication:
Structural Journal
Volume:
123
Issue:
2
Appears on pages(s):
145-156
Keywords:
bar size factor; bond; development length; high-strength reinforcement; lap splice; large bar
DOI:
10.14359/51749168
Date:
3/1/2026
Abstract:
Eleven large-scale reinforced concrete beams were tested to failure under four-point bending to investigate tension lap splices of No. 14 and 18 (43 and 57 mm) bars. Additional variables included transverse reinforcement, concrete compressive strength (nominally 5 or 10 ksi [34 or 69 MPa]), and target bar stress at splice failure (60 or 100 ksi [420 or 690 MPa]). Results show that both the ACI 408R-03 and ACI 318-19 bond length equations become less conservative as bar diameter increases, so a bar size factor is proposed for modifying bond length equations to obtain similar conservatism across all diameters. A minimum clear cover of one bar diameter is also recommended for large-bar lap splices. Increasing the limit on (cb + Ktr)/db in the ACI 318-19 development length equation from 2.5 to 4.0 was shown to produce similar mean ratios of test-to-calculated bar stresses across different amounts of transverse reinforcement. Finally, results suggest that development length should be limited to 50db when designing lap splices without transverse reinforcement.
Related References:
1. ACI Committee 318, “Building Code Requirements for Reinforced Concrete (ACI 318-19) and Commentary (ACI 318R-19) (Reapproved 2022),” American Concrete Institute, Farmington Hills, MI, 2019, 624 pp.
2. AASHTO LRFD, LRFD Bridge Design Specifications, tenth edition, American Association of State Highway and Transportation Officials, Washington, DC, 2024, 1905 pp.
3. ACI Committee 408, “Bond and Development of Straight Reinforcing Bars in Tension (ACI 408R-03),” American Concrete Institute, Farmington Hills, MI, 2003, 49 pp.
4. Ferguson, P. M., and Thompson, J. N., “Development Length for Large High Strength Reinforcing Bars,” ACI Journal Proceedings, V. 62, No. 1, Jan. 1965, pp. 71-94.
5. Ferguson, P. M., and Krishnaswamy, C. N., “Tensile Lap Splices Part 2: Design Recommendations for Retaining Wall Splices and Large Bar Splices,” Report No. 113-3, Texas Highway Department, Austin, TX, 1971, 60 pp.
6. Thompson, M. A.; Jirsa, J. O.; Breen, J. E.; and Meinheit, D. F., “Behavior of Multiple Lap Splices in Wide Sections,” ACI Journal Proceedings, V. 76, No. 2, Mar.-Apr. 1979, pp. 227-248.
7. Ichinose, T.; Kanayama, Y.; Inoue, Y.; and Bolander, J. E. Jr., “Size Effect on Bond Strength of Deformed Bars,” Construction and Building Materials, V. 18, No. 7, 2004, pp. 549-558. doi: 10.1016/j.conbuildmat.2004.03.014
8. Hassan, T. K.; Lucier, G. W.; and Rizkalla, S. H., “Splice Strength of Large Diameter, High Strength Steel Reinforcing Bars,” Construction and Building Materials, V. 26, No. 1, 2012, pp. 216-225. doi: 10.1016/j.conbuildmat.2011.06.013
9. Hegger, J.; Schnell, J.; Empelmann, M.; Schoening, J.; Schäfer, M.; and Oettel, V., “Weiterentwicklung von Bemessungs- und Konstruktionsregeln bei großen Stabdurchmessern (>Ø 32 mm, B500),” final report, Research Project 16992 N/1, German Federation of Industrial Research Associations (AiF), 2015.
10. fib, Model Code for Concrete Structures (2010), Thomas Telford, Comité Euro-International du Béton, Lausanne, Switzerland, 2013, 434 pp.
11. Rulon, R.; Lequesne, R. D.; Lepage, A.; and Darwin, D., “Lap Splicing of Large High-Strength Steel Reinforcing Bars,” SM Report No. 148, University of Kansas Center for Research, Inc., 2022, 136 pp., hdl.handle.net/1808/32586. (last accessed Jan. 28, 2026)
12. ASTM E8/E8M-21, “Standard Test Methods for Tension Testing of Metallic Materials,” ASTM International, West Conshohocken, PA, 2021, 30 pp.
13. ASTM A370-21, “Standard Test Methods and Definitions for Mechanical Testing of Steel Products,” ASTM International, West Conshohocken, PA, 2021, 50 pp.
14. ASTM C39/C39M-21, “Standard Test Method for Compressive Strength of Cylindrical Concrete Specimens,” ASTM International, West Conshohocken, PA, 2021, 8 pp.
15. Hognestad, E., “A Study of Combined Bending and Axial Load in Reinforced Concrete Members,” Bulletin Series No. 399, University of Illinois Engineering Experiment Station, 1951, 134 pp.
16. Seliem, H. M.; Hosny, A.; Rizkalla, S.; Zia, P.; Briggs, M.; Miller, S.; Darwin, D.; Browning, J.; Glass, G. M.; Hoyt, K.; Donnelly, K.; and Jirsa, J. O., “Bond Characteristics of ASTM A1035 Steel Reinforcing Bars,” ACI Structural Journal, V. 106, No. 4, July-Aug. 2009, pp. 530-539.
17. ACI Committee 408, Tension Lap Splice Database (04-2021), American Concrete Institute, https://www.concrete.org/store/productdetail.aspx?ItemID=408DB&Format=EXCEL&Language=English&Units=US_AND_METRIC, 2021. (last accessed Feb. 10, 2026)
18. Richter, B. P., “A New Perspective on the Tensile Strength of Lap Splices in Reinforced Concrete Members,” MS thesis, Purdue University, West Lafayette, IN, 2012, 165 pp.
19. Frosch, R.; Fleet, E.; and Glucksman, R., Development and Splice Lengths for High-Strength Reinforcement, Volume I: General Bar Development, Charles Pankow Foundation, 2020, 333 pp.
20. Şener, S.; Bažant, Z. P.; and Becq-Giraudon, E., “Size Effect on Failure of Bond Splices of Steel Bars in Concrete Beams,” Journal of Structural Engineering, ASCE, V. 125, No. 6, 1999, pp. 577-703. doi: 10.1061/(ASCE)0733-9445(1999)125:6(653)
21. Schoening, J. C., “Anchorages and Laps in Reinforced Concrete Members under Monotonic Loading,” PhD dissertation, RWTH Aachen University, Aachen, Germany, 2018, 394 pp.