Flexural Behavior of Double-Layer Concrete Beams Composed of Normal and Steel Fiber-Reinforced Concrete

Authors

• Shaida Rasul Abdalrahman, Civil Engineering Department, Erbil Technical Engineering College, Erbil Polytechnic University, Erbil-Iraq.Follow
• Ayad Zaki Saber Agha, Civil Engineering Department, Erbil Technical Engineering College, Erbil Polytechnic University, Erbil-Iraq.Follow

How to Cite This Article

Abdalrahman, Shaida Rasul and Agha, Ayad Zaki Saber (2026) "Flexural Behavior of Double-Layer Concrete Beams Composed of Normal and Steel Fiber-Reinforced Concrete," Polytechnic Journal: Vol. 16: Iss. 1, Article 1.
DOI: https://doi.org/10.59341/2707-7799.1869

Document Type

Original Article

Abstract

This investigation studies the flexural performance of double-layer reinforced concrete beams composed of ordinary concrete and steel fiber reinforced concrete (SFRC). The study evaluates the effects of bottom layer thickness, shear span ratio (a/d) and straight steel fiber volume fraction on structural behavior. The study project comprises twenty reinforced concrete beams, all specimens had across-section size of (125 mm × 250 mm) and different length of (1300, 1740, 2180) mm. The specimens were simple support and strengthened with flexural reinforcement of (4Ø12mm) and transverse reinforcement employing (Ø10@110mm) bars as stirrups. The results demonstrate that the double-layer concrete configuration significantly improves crack control, resulting in reduced crack widths compared with conventional beams. Increasing the shear span ratio from (2, 3 and 4) increased the crack widths and reduced the ultimate load capacity by (33.1% and 47.23%) respectively. Augmenting the thickness of the bottom layer of SFRC resulted in a rise in the ultimate failure load when =0.5% by (0.8%, 4.9%, 12% and 19.1%) and when =1% by (7.4%, 12%, 17.7% and 21.8%) in comparison to the control beam with the complete thickness of conventional concrete. These findings confirm that incorporating SFRC in the tension zone of double-layer beams effectively enhances flexural capacity, crack resistance, and overall structural performance

Receive Date

7/11/2025

Revise Date

31/12/2025

Accept Date

15/1/2026

Publication Date

3-1-2026

References

[1] Jazlan NA, Goh LD, Ahmad H, Ismail R, Ahmad Zakwan FA, Wahid N, et al. The influence of steel fiber type on the flexural performance of steel fibre reinforced concrete beam. J Sustain Civil Eng Technol 2025;4(2):1—16. https://doi.org/10.24191/jscet.v4i2.jscet_s_000027.

[2] Jang SJ, Jeong GY, Lee MH, Rokugo K, Yun HD. Compressive strength effects on flexural behavior of steel fiber reinforced concrete. Key Eng Mater 2016;709:101—4. https://doi.org/10.4028/www.scientific.net/kem.709.101.

[3] Yoo D-Y, Moon D-Y. Effect of steel fibers on the flexural behavior of RC beams with very low reinforcement ratios. Constr Build Mater 2018;188:237—54. https://doi.org/10.1016/ j.conbuildmat.2018.08.099.

[4] Zhao L, Chen G, Huang C. Experimental investigation on the flexural behavior of concrete reinforced by various types of steel fibers. Front Mater 2023;10:1301647. https://doi. org/10.3389/fmats.2023.1301647.

[5] Altun F, Haktanir T, Ari K. Effects of steel fiber addition on mechanical properties of concrete and RC beams. Constr Build Mater 2007;21(3):654—61. https://doi.org/10.1016/j. conbuildmat.2005.12.006.

[6] Nematzadeh M, Fallah-Valukolaee S. Experimental and analytical investigation on structural behavior of two-layer fiber-reinforced concrete beams reinforced with steel and GFRP rebars. Constr Build Mater 2021;273:121933. https:// doi.org/10.1016/j.conbuildmat.2020.121933.

[7] Lu Z, Fan X, Chen Y. Mechanical properties of layered steel fiber and hybrid fiber reinforced concrete. J Wuhan Univ Technol Materials Sci Ed 2008;23(5):733—6. https://doi. org/10.1007/s11595-007-5733-7.

[8] Mohamed SI, Ibrahim MM, Sherif ME. Influence of fibers on flexural behavior and ductility of concrete beams reinforced with GFRP rebars. Eng Struct 2011;33(5):1754—63. https://doi.org/10.1016/j.engstruct.2011.02.014.

[9] Deformation and ultimate strength in flexure of reinforced concrete beams made with steel fiber concrete. In: Swamy R, Sa’ad A, editors. Journal Proceedings; 1981. https://doi.org/10.14359/10525.

[10] Danying G, Zhiqiang G, Haitang Z, Yunchao H. Fatigue behavior assessment for steel fiber reinforced concrete beams through experiment and Fatigue Prediction Model. S.R. Abdalrahman, A.Z. Saber Agha / Polytechnic Journal 16 (2026) 1—18 17 Structures 2020;27:1105—17. https://doi.org/10.1016/j.istruc. 2020.07.028.

[11] Nematzadeh M, Karimi A, Fallah-Valukolaee S. Compressive performance of steel fiber-reinforced rubberized concrete core detached from heated CFST. Constr Build Mater 2020; 239:117832. https://doi.org/10.1016/j.conbuildmat.2019.117832.

[12] Fallah S, Nematzadeh M. Mechanical properties and durability of high-strength concrete containing macro-polymeric and polypropylene fibers with nano-silica and silica fume. Constr Build Mater 2017;132:170—87. https://doi.org/10.1016/ j.conbuildmat.2016.11.100.

[13] Doo-Yeol Y, Nemkumar B, Young-Soo Y. Predicting service deflection of ultra-high-performance fiber-reinforced concrete beams reinforced with GFRP bars. Compos B Eng 2016; 99:381—97. https://doi.org/10.1016/j.compositesb.2016.06.013.

[14] Chellapandian M, Mani A, Prakash SS. Effect of macrosynthetic structural fibers on the flexural behavior of concrete beams reinforced with different ratios of GFRP bars. Compos Struct 2020;254:112790. https://doi.org/10.1016/j. compstruct.2020.112790.

[15] Huanzi W, Abdeldjelil B. Ductility characteristics of fiberreinforced-concrete beams reinforced with FRP rebars. Constr Build Mater 2011;25(5):2391—401. https://doi. org/10.1016/j.conbuildmat.2010.11.040.

[16] Najm HB, Rasheed MHF. Flexural behavior of two-layers reinforced concrete beams. Polytech J 2022;12(2):180—92. https://doi.org/10.25156/ptj.v12n2y2022.pp180-192.

[17] Iskhakov I, Ribakov Y. A design method for two-layer beams consisting of normal and fibered high strength concrete. Mater Des 2007;28(5):1672—7. https://doi.org/10.1016/j. matdes.2006.03.017.

[18] Iskhakov I, Ribakov Y. Two-layer pre-stressed beams consisting of normal and steel fibered high strength concrete. Mater Des 2008;29(8):1616—22. https://doi.org/10.1016/j. matdes.2007.04.013.

[19] Holschemacher K, Iskhakov I, Ribakov Y, Mueller T. Laboratory tests of two-layer beams consisting of normal and fibered high strength concrete: ductility and technological aspects. Mech Adv Mater Struct 2012;19(7):513—22. https:// doi.org/10.1080/15376494.2011.556840.

[20] Iskhakov I, Ribakov Y, Holschemacher KJSC. Experimental investigation of continuous two-layer reinforced concrete beams. Struct Concr 2017;18(1):205—15. https://doi. org/10.1002/suco.201600027.

[21] Altun F, Haktanir T, Ari K. Effects of steel fiber addition on mechanical properties of concrete and RC beams. Constr Build Mater 2007;21(3):654—61. https://doi.org/10.1016/j. conbuildmat.2005.12.006.

[22] Nataraja MC, Dhang N, Gupta AP. Stress—strain curves for steel-fiber reinforced concrete under compression. Cement Concr Compos 1999;21(5):383—90. https://doi.org/10.1016/S0 958-9465(99)00021-9.

[23] Pereira DR, Piteri MA, Souza AN, Papa JP, Adeli H. FEMa: a finite element machine for fast learning. Neural Comput Appl 2020;32(10):6393—404. https://doi.org/10.1007/s00521-019-041 46-4.

[24] Yang I-H, Park J, Bui TQ, Kim K-C, Joh C, Lee H. An experimental study on the ductility and flexural toughness of ultrahigh-performance concrete beams subjected to bending. Materials 2020;13(10):2225. https://doi.org/10.3390/ma13102225.

[25] Xu H, Humar J. Damage detection in a girder bridge by artificial neural network technique. Comput Aided Civ Infrastruct Eng 2006;21(6):450—64. https://doi.org/10.1111/j.1 467-8667.2006.00449.x.

[26] Finckh W, Zilch K. Strengthening and rehabilitation of reinforced concrete slabs with carbon-fiber reinforced polymers using a refined bond model. Comput Aided Civ Infrastruct Eng 2012;27(5):333—46. https://doi.org/10.1111/j.1 467-8667.2011.00752.x.

[27] Zhang R, Jin L, Tian Y, Dou G, Du X. Static and dynamic mechanical properties of eco-friendly polyvinyl alcohol fiber-reinforced ultra-high-strength concrete. Struct Concr 2019;20(3):1051—63. https://doi.org/10.1002/suco.201800247.

[28] Li C, Zhu H, Niu G, Cheng S, Gu Z, Yang L. Flexural behavior and a new model for flexural design of concrete beams hybridly reinforced by continuous FRP bars and discrete steel fibers. Structures 2022;38:949—60. https://doi. org/10.1016/j.istruc.2022.02.037.

[29] Soner G, Behice O, € Zehra Funda A. Workability, strength and toughness properties of different types of fiber-reinforced wet-mix shotcrete. Structures 2021;31:781—91. https:// doi.org/10.1016/j.istruc.2021.02.031.

[30] Nataraja MC, Dhang N, Gupta AP. Toughness characterization of steel fiber-reinforced concrete by JSCE approach. Cement Concr Res 2000;30(4):593—7. https://doi.org/10.1016/ S0008-8846(00)00212-X.

[31] Guo Y, Yuan D, Wei B, Hu Y. Structural damage identification method of concrete dam based on multi-fidelity surrogate model collaboratively corrected by monitoring and simulation information. Adv Eng Inform 2025;67:103559. https://doi.org/10.1016/j.aei.2025.103559.

[32] Vidal N, Lopez-Villegas JM, Cairo  I, Garcia-Miquel A, Romeu J, Jofre LL. Encapsulated UHF antenna for early and long-term concrete monitoring. Measurement 2025;243:11 6439. https://doi.org/10.1016/j.measurement.2024.116439.

[33] Dancygier A, Savir Z. Effects of steel fibers on shear behavior of high-strength reinforced concrete beams. Adv Struct Eng 2011;14(5):745—61. https://doi.org/10.1260/1369-4332.14.5.745.

[34] Pratama MMA, Vertian T, Umniati BS, Yoh WH. Flexural behaviour of the functionally graded concrete beams using two-layers and three-layers configuration. IOP Conf Ser Mater Sci Eng 2019;669(1):012054. https://doi.org/10.1088/1 757-899x/669/1/012054.

[35] Qian R, Shao Y, He R, Fu C, Zhang Y. Investigations on the non-uniform corrosion-induced crack of hybrid steel-fiber concrete beams. Structures 2025;80:109972. https://doi. org/10.1016/j.istruc.2025.109972.

[36] Jun-Mo Y, Kyung-Hwan M, Hyun-Oh S, Young-Soo Y. Effect of steel and synthetic fibers on flexural behavior of high-strength concrete beams reinforced with FRP bars. Compos B Eng 2012;43(3):1077—86. https://doi.org/10.1016/j. compositesb.2012.01.044.

[37] Ovitigala T, Ibrahim MA, Issa MA. Serviceability and ultimate load behavior of concrete beams reinforced with basalt fiber-reinforced polymer bars. ACI Struct J 2016;11 3(4). https://doi.org/10.14359/51688752.

[38] Bischoff PH. Serviceability and ultimate load behavior of concrete beams reinforced with basalt fiber-reinforced polymer bars. ACI Struct J 2017;114(4):1067—72. https://doi. org/10.14359/51688752.

[39] Shupeng Z, Zihan J, Qingyou O, Junkai L, Chuanlin W. Analysis on flexural toughness of steel fiber reinforced concrete based on acoustic emission and digital image correlation techniques. Constr Build Mater 2025;492:143039. https://doi.org/10.1016/j.conbuildmat.2025.143039.

[40] Afroughsabet V, Biolzi L, Ozbakkaloglu T. High-performance fiber-reinforced concrete: a review. J Mater Sci 2016; 51(14):6517—51. https://doi.org/10.1007/s10853-016-9917-4.

[41] Kwak Y-K, Eberhard MO, Kim W-S, Kim J. Shear strength of steel fiber-reinforced concrete beams without stirrups. ACI Struct J 2002;99(4):530—8. https://doi.org/10.14359/12122.

[42] Yoo D-Y, Banthia N, Yoon Y-S. Flexural behavior of ultrahigh-performance fiber-reinforced concrete beams reinforced with GFRP and steel rebars. Eng Struct 2016;111: 246—62. https://doi.org/10.1016/j.engstruct.2015.12.003.

[43] Dinh HH. Shear behavior of steel fiber reinforced concrete beams without stirrup reinforcement. University of Michigan; 2009. https://doi.org/10.14359/51663913.

[44] Salna R, Marciukaitis G. The influence of shear span ratio on load capacity of fibre reinforced concrete elements with various steel fibre volumes. J Civ Eng Manag 2007;13(3):20 9—16. https://doi.org/10.3846/13923730.2007.9636439.

[45] Ali MA, White RN. Consideration of compression stress bulging and strut degradation in truss modeling of ductile and brittle corbels. Eng Struct 2001;23(3):240—9. https://doi. org/10.1016/S0141-0296(00)00040-7.