Experimental Evaluation of Damaged Reinforced Concrete Slabs with Openings Strengthened Using Externally Bonded FRP Sheets

Authors

  • Cong Bang Truong

    Faculty of Civil Engineering, Mien Tay Construction University, Vinh Long 85119, Vietnam
  • Hoang Khang Lam

    Center for Continuing Education, Mien Tay Construction University, Vinh Long 85119, Vietnam
  • Hong Dat Nguyen

    Faculty of Civil Engineering, Mien Tay Construction University, Vinh Long 85119, Vietnam

DOI:

https://doi.org/10.30564/jbms.v8i3.13572
Received: 28 May 2026 | Revised: 9 June 2026 | Accepted: 6 July 2026 | Published Online: 18 August 2026

Abstract

Openings made in reinforced concrete (RC) slabs can disturb force transfer and reduce stiffness, particularly when the slab has already been damaged. This paper reports the second-stage test of six RC slab specimens that had been loaded previously under concentrated column loading. After the first-stage tests, the damaged slabs were repaired with epoxy and strengthened with one externally bonded FRP N300 sheet layer on the bottom face. The FRP sheet covered the slab soffit; for specimens with openings, the sheet was cut out at the opening region. The specimens included slabs without openings, slabs with square and circular openings, a slab with a larger square opening, a slab with an offset square opening, and one slab with a modified reinforcement arrangement inherited from the original specimens. The strengthened slabs were re-tested under incremental column loading. Vertical displacement, compressive strain, tensile strain, visible surface response, and FRP debonding were recorded. Since the tensile face was covered by FRP, crack propagation on the bottom surface was not directly observable during re-testing. The results show that FRP strengthening improved the response of several damaged slabs at higher load levels, but the improvement depended on opening geometry, opening location, inherited reinforcement layout, and bond condition. Final failure was governed mainly by FRP debonding. S6 showed the most favorable response among the tested specimens, although this result should be interpreted together with the absence of an opening and its modified reinforcement arrangement.

Keywords:

Reinforced Concrete Slab; Slab Opening; Damaged Slab; FRP Sheet; Strengthening; Load–Deflection; Strain Response

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How to Cite

Truong, C. B., Lam, H. K., & Nguyen, H. D. (2026). Experimental Evaluation of Damaged Reinforced Concrete Slabs with Openings Strengthened Using Externally Bonded FRP Sheets. Journal of Building Material Science, 8(3), 122–142. https://doi.org/10.30564/jbms.v8i3.13572

Issue

Vol. 8, Iss. 3 (September 2026): In Progress

Article Type

Article

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Copyright © 2026 Cong Bang Truong, Hoang Khang Lam, Hong Dat Nguyen

Creative Commons License

This is an open access article under the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) License.

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