Experimental Assessment for Restoring the Flexural Strength of Severely Damaged RC Beams Using NSM Steel Bars and External Confinement

Articles in Press

Document Type : Original Article

Authors

1 Department of Civil Engineering, Engineering College/ Kufa University, Najaf, Iraq

2 Department of Civil Engineering, Babol Noshirvani University of Technology, Babol, Iran

Abstract

Reinforced concrete beams may require repair to regain lost capacity due to unforeseen events, such as accidents or loading exceeding the limits that weren't predicted in the design. The purpose of this research is to restore the load capacity of RC beams after severe mid-span damage. Eight reinforced concrete beams were utilized in this study. A near-surface mounting (NSM) technique was examined, with various variables including the configuration of repair bars, adhesive materials, diameter of repair bars, as well as externally bonded repair with a steel plate in the damaged zone. The result revealed that straight bars restored up to 94.5% of ultimate strength, while hooked bars slightly exceeded the control by 5%. Epoxy bonds achieved up to 105.6% recovery, surpassing cementitious systems that ranged from 66.8% to 110.6%. Larger repairing bars of 16 mm restored capacities up to 115.6%, significantly higher than the recovery range from 66.8% to 82.4% for 12 mm bars. Confinement raised the ultimate load marginally above control, of 5.4%, while unconfined beams recovered only 82.4%. Cementitious adhesives offered an economical repair option for moderate-demand applications; however, both bonding systems reduced ductility by up to 55.6% and energy absorption by up to 89.3%. Straight bars improved stiffness and ductility compared with hooked bars, while larger bar diameters of 16 mm reduced performance losses and enhanced stiffness. Confinement improved service stiffness and partially limited energy-absorption losses, although ductility remained below that of the control beam.

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References

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Articles in Press, Accepted Manuscript
Available Online from 10 June 2026

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History

  • Receive Date: 15 April 2026
  • Revise Date: 03 May 2026
  • Accept Date: 10 June 2026
  • First Publish Date: 10 June 2026

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