Title:
Strength of Lap-Spliced Glass Fiber-Reinforced Polymer Reinforcing Bar in Eccentrically Loaded Concrete Columns
Author(s):
Ibrahim Zidan, Hamdy M. Mohamed, and Brahim Benmokrane
Publication:
Structural Journal
Volume:
123
Issue:
4
Appears on pages(s):
309-320
Keywords:
columns; design codes; eccentric loading; glass fiber- reinforced polymer (GFRP) reinforcement; interaction diagram; load- displacement; reinforced concrete (RC); splice length; splice strength
DOI:
10.14359/51750670
Date:
7/1/2026
Abstract:
Over the last two decades, the literature has focused on using glass fiber-reinforced polymer (GFRP) bars in compression members. Nonetheless, several aspects have yet to be explored. One such aspect is the lap splicing of GFRP reinforcement. Limited research has examined the splice strength of GFRP bars in concentric compression members. None has been performed on eccentrically loaded columns with lap-spliced bars. In the current study, nine full-scale GFRP-reinforced concrete columns measuring 305 mm in diameter and 1600 mm in length with splices in both compression and tension were tested under moderate, high, and extreme eccentricity. The splice lengths used were 12db, 24db, and 36db for each eccentricity. In addition, five similar specimens from the literature were used for comparison: two had 24db and 36db splice lengths and were tested under concentric loading; the other three had continuous bars tested under different eccentricities. The comparison was in terms of load-displacement curves, load-splice strength curves, and the contribution of splice components. The experimental results were compared to the provisions provided in ACI CODE-440.11-22 and CSA S6:25. An interaction diagram based on the recommendations of CSA S806-12 was also drawn and compared to the interaction diagram of the experimental data. Test results indicate that the end bearing was considerable and is a critical factor, especially at moderate eccentricity. Furthermore, the columns with spliced bars showed higher peak loads than the columns with continuous bars, and splice length had a positive effect on splice strength and peak load. The analysis shows that the equations in ACI CODE-440.11-22 and CSA S6:25 are significantly conservative. The results of this research will inform the development of new and accurate design equations for economical lap splices in subsequent phases of the study. They will also encourage design codes to consider end bearing in compression splices.
Related References:
AASHTO, 2018, “AASHTO LRFD Bridge Design Guide Specifications for GFRP-Reinforced Concrete,” second edition, American Association of State Highway and Transportation Officials, Washington, DC, 121 pp.
Abdelazim, W.; Mohamed, H. M.; and Benmokrane, B., 2020c, “Inelastic Second-Order Analysis for Slender GFRP-Reinforced Concrete Columns: Experimental Investigations and Theoretical Study,” Journal of Composites for Construction, ASCE, V. 24, No. 3, June, p. 04020016. doi: 10.1061/(ASCE)CC.1943-5614.0001019
Abdelazim, W.; Mohamed, H. M.; Afifi, M. Z.; and Benmokrane, B., 2020b, “Proposed Slenderness Limit for Glass Fiber-Reinforced Polymer-Reinforced Concrete Columns Based on Experiments and Buckling Analysis,” ACI Structural Journal, V. 117, No. 1, Jan., pp. 241-254. doi: 10.14359/51718073
Abdelazim, W.; Mohamed, H. M.; Benmokrane, B.; and Afifi, M. Z., 2020a, “Effect of Critical Test Parameters on Behavior of Glass Fiber-Reinforced Polymer-Reinforced Concrete Slender Columns under Eccentric Load,” ACI Structural Journal, V. 117, No. 4, July, pp. 127-141. doi: 10.14359/51723507
Abdelazim, W.; Mohamed, H. M.; Benmokrane, B.; and Nolan, S., 2020d, “Strength of Bridge High-Strength Concrete Slender Compression Members Reinforced with GFRP Bars and Spirals: Experiments and Second-Order Analysis,” Journal of Bridge Engineering, ASCE, V. 25, No. 9, Sept., p. 04020066. doi: 10.1061/(ASCE)BE.1943-5592.0001601
ACI Committee 440, 2015, “Guide for the Design and Construction of Structural Concrete Reinforced with Fiber-Reinforced Polymer (FRP) Bars (ACI 440.1R-15),” American Concrete Institute, Farmington Hills, MI, 88 pp.
ACI Committee 440, 2022, “Building Code Requirements for Structural Concrete Reinforced with Glass Fiber- Reinforced Polymer (GFRP) Bars—Code and Commentary (ACI CODE-440.11-22),” American Concrete Institute, Farmington Hills, MI, 260 pp.
Afifi, M. Z.; Mohamed, H. M.; Chaallal, O.; and Benmokrane, B., 2015, “Confinement Model for Concrete Columns Internally Confined with Carbon FRP Spirals and Hoops,” Journal of Structural Engineering, ASCE, V. 141, No. 9, Sept., p. 04014219. doi: 10.1061/(ASCE)ST.1943-541X.0001197
ASTM D7205/D7205M-21, 2021, “Standard Test Method for Tensile Properties of Fiber Reinforced Polymer Matrix Composite Bars,” ASTM International, West Conshohocken, PA, 13 pp.
Benmokrane, B.; Mohamed, H. M.; Mousa, S.; Elsafty, A.; and Nolan, S., 2021, “Design, Construction, Testing, and Behavior of Driven Precast Concrete Piles Reinforced with GFRP Bars and Spirals,” Journal of Bridge Engineering, ASCE, V. 26, No. 8, Aug., p. 04021050. doi: 10.1061/(ASCE)BE.1943-5592.0001755
Chun, S., 2017, “Components of Compression Splice Resistances in High-Strength Concrete,” Magazine of Concrete Research, V. 69, No. 10, Mar., pp. 502-511. doi: 10.1680/jmacr.16.00412
Chun, S.-C.; Lee, S.-H.; and Oh, B., 2010a, “Compression Lap Splice in Unconfined Concrete of 40 and 60 MPa (5800 and 8700 psi) Compressive Strengths,” ACI Structural Journal, V. 107, No. 2, Mar.-Apr., pp. 170-178.
Chun, S.-C.; Lee, S.-H.; and Oh, B., 2010b, “Compression Splices in Confined Concrete of 40 and 60 MPa (5800 and 8700 psi) Compressive Strengths,” ACI Structural Journal, V. 107, No. 4, July-Aug., pp. 476-485.
Chun, S.-C.; Lee, S.-H.; and Oh, B., 2011, “Compression Splices in High-Strength Concrete of 100 MPa (14,500 psi) and Less,” ACI Structural Journal, V. 108, No. 6, Nov.-Dec., pp. 715-724.
CSA S6:25, 2025, “Canadian Highway Bridge Design Code,” CSA Group, Toronto, ON, Canada, 1478 pp.
CSA S806-12 (R2021), 2012, “Design and Construction of Building Structures with Fibre-Reinforced Polymers (Reaffirmed in 2021),” CSA Group, Toronto, ON, Canada, 201 pp.
El-Bayome, E.; Hassanli, R.; Zhuge, Y.; Bazli, M.; Elchalakani, M.; and Manalo, A., 2025, “Analytical Investigation of Axial-Moment Interaction Behaviour of GFRP-RC Piles Made of High-Strength and Ultra-High-Performance Concrete,” Structures, V. 74, Apr., Article No. 108493. doi: 10.1016/j.istruc.2025.108493
Elhamaymy, A.; Mohamed, H. M.; and Benmokrane, B., 2021, “Durability Assessment and Behavior under Axial Load of Circular GFRP-RC Piles Conditioned in Severe Simulated Marine Environment,” Engineering Structures, V. 249, Dec., Article No. 113376. doi: 10.1016/j.engstruct.2021.113376
Elhamaymy, A.; Mohamed, H. M.; and Benmokrane, B., 2023, “Performance of Glass Fiber-Reinforced Polymer-Reinforced Concrete Piles Exposed to Laboratory-Simulated Marine Environments,” ACI Structural Journal, V. 120, No. 3, May, pp. 31-45. doi: 10.14359/51738501
Elmesalami, N.; Abed, F.; and El Refai, A., 2021, “Concrete Columns Reinforced with GFRP and BFRP Bars under Concentric and Eccentric Loads: Experimental Testing and Analytical Investigation,” Journal of Composites for Construction, ASCE, V. 25, No. 2, Apr., p. 04021003. doi: 10.1061/(ASCE)CC.1943-5614.0001115
Farhangdoust, S.; Mehrabi, A.; and Nolan, S., 2022, “GFRP Composite Bars for Splicing Prestressed Precast Concrete Piles: Design and Experimental Investigation,” Engineering Structures, V. 272, Dec., Article No. 114969. doi: 10.1016/j.engstruct.2022.114969
Guérin, M.; Mohamed, H. M.; Benmokrane, B.; Nanni, A.; and Shield, C. K., 2018a, “Eccentric Behavior of Full-Scale Reinforced Concrete Columns with Glass Fiber-Reinforced Polymer Bars and Ties,” ACI Structural Journal, V. 115, No. 2, Mar., pp. 489-499. doi: 10.14359/51701107
Guérin, M.; Mohamed, H. M.; Benmokrane, B.; Shield, C. K.; and Nanni, A., 2018b, “Effect of Glass Fiber-Reinforced Polymer Reinforcement Ratio on Axial-Flexural Strength of Reinforced Concrete Columns,” ACI Structural Journal, V. 115, No. 4, July, pp. 1049-1061. doi: 10.14359/51701279
Hadhood, A.; Mohamed, H. M.; and Benmokrane, B., 2017a, “Experimental Study of Circular High-Strength Concrete Columns Reinforced with GFRP Bars and Spirals under Concentric and Eccentric Loading,” Journal of Composites for Construction, ASCE, V. 21, No. 2, Apr., p. 04016078. doi: 10.1061/(ASCE)CC.1943-5614.0000734
Hadhood, A.; Mohamed, H. M.; and Benmokrane, B., 2017b, “Failure Envelope of Circular Concrete Columns Reinforced with Glass Fiber-Reinforced Polymer Bars and Spirals,” ACI Structural Journal, V. 114, No. 6, Nov.-Dec., pp. 1417-1428. doi: 10.14359/51689498
Hadhood, A.; Mohamed, H. M.; Ghrib, F.; and Benmokrane, B., 2017c, “Efficiency of Glass-Fiber Reinforced-Polymer (GFRP) Discrete Hoops and Bars in Concrete Columns under Combined Axial and Flexural Loads,” Composites Part B: Engineering, V. 114, Apr., pp. 223-236. doi: 10.1016/j.compositesb.2017.01.063
Hu, X.; Xue, W.; Jiang, J.; Yu, T.; Wang, X.; Zheng, Y.; and Zeng, J., 2025, “Evaluation of Splice Length of Large-Diameter GFRP Bars in UHPC,” Journal of Building Engineering, V. 108, Aug., Article No. 112925. doi: 10.1016/j.jobe.2025.112925
Jaitrong, J.; Sirimontree, S.; and Thongchom, C., 2025, “Axial Compression Behavior of Square Concrete Columns Reinforced with Longitudinal and Transverse GFRP Bars,” Results in Engineering, V. 26, June, Article No. 105032. doi: 10.1016/j.rineng.2025.105032
Pan, Y.; Wang, J.; Mogul, A. P.; He, J.; and Xu, G., 2025, “Enhanced Durability Assessment of GFRP and HFRP Bars Embedded in Mortar under Simulated Seawater Exposure,” Journal of Building Engineering, V. 111, Oct., Article No. 113563. doi: 10.1016/j.jobe.2025.113563
Pfister, J. F., and Mattock, A. H., 1963, “High Strength Bars as Concrete Reinforcement, Part 5. Lapped Splices in Concentrically Loaded Columns,” PCA Research and Development Laboratories, V. 5, No. 2, May, pp. 27-40.
Spagnuolo, S.; Giorgi, C.; Rinaldi, Z.; and Pedrocco, L., 2023, “Precast High-Performance Concrete (HPC) Sheet Piles Prestressed with Glass Fiber Reinforced Polymer (GFRP) Bars,” Composite Structures, V. 304, Part 1, Jan., Article No. 116324. doi: 10.1016/j.compstruct.2022.116324
Tabatabaei, A.; Eslami, A.; Mohamed, H. M.; and Benmokrane, B., 2018, “Strength of Compression Lap-Spliced GFRP Bars in Concrete Columns with Different Splice Lengths,” Construction and Building Materials, V. 182, Sept., pp. 657-669. doi: 10.1016/j.conbuildmat.2018.06.154
Tabatabaei, A.; Eslami, A.; Mohamed, H. M.; and Benmokrane, B., 2019, “Compression Splices of GFRP Bars in Unconfined and Confined Concrete Columns,” Journal of Composites for Construction, ASCE, V. 23, No. 6, Dec., p. 04019046. doi: 10.1061/(ASCE)CC.1943-5614.0000974
Tabatabaei, A.; Mohamed, H. M.; Eslami, A.; and Benmokrane, B., 2020, “Proposed Design Equations for Lap Splice of Glass Fiber-Reinforced Polymer Bars under Compression in Concrete,” ACI Structural Journal, V. 117, No. 2, Mar., pp. 291-302. doi: 10.14359/51721370
Tekle, B. H.; Khennane, A.; and Kayali, O., 2017, “Bond of Spliced GFRP Reinforcement Bars in Alkali Activated Cement Concrete,” Engineering Structures, V. 147, Sept., pp. 740-751. doi: 10.1016/j.engstruct.2017.06.040
Zidan, I.; Khalaf, M. A.; and Helmy, A. I. I., 2023, “Properties of Alkali-Activated Slag Mortar and Prediction of Its Compressive Strength,” Ain Shams Engineering Journal, V. 14, No. 11, Nov., Article No. 102536. doi: 10.1016/j.asej.2023.102536