Interaction between steel stirrups and shear-strengthening FRP strips in RC beams

G. M. Chen, Jinguang Teng, J. F. Chen, O. A. Rosenboom

Research output: Journal article publicationJournal articleAcademic researchpeer-review

108 Citations (Scopus)


RC beams shear strengthened with either fiber-reinforced polymer (FRP) U-jackets/U-strips or side strips commonly fail due to debonding of the bonded FRP shear reinforcement. As such debonding occurs in a brittle manner at relatively small shear crack widths, some of the internal steel stirrups may not have reached yielding. Consequently, the yield strength of internal steel stirrups in such a strengthened RC beam cannot be fully used. In this paper, a computational model for shear interaction between FRP strips and steel stirrups is first presented, in which a general parabolic crack shape function is employed to represent the widening process of a single major shear crack in an RC beam. In addition, appropriate bond-slip relationships are adopted to accurately depict the bond behavior of FRP strips and steel stirrups. Numerical results obtained using this computational model show that a substantial adverse effect of shear interaction generally exists between steel stirrups and FRP strips for RC beams shear strengthened with FRP side strips. For RC beams shear strengthened with FRP U-strips, shear interaction can still have a significant adverse effect when FRP strips with a high axial stiffness are used. Therefore, for accurate evaluation of the shear resistance of RC beams shear strengthened with FRP strips, this adverse effect of shear interaction should be properly considered in design.
Original languageEnglish
Pages (from-to)498-509
Number of pages12
JournalJournal of Composites for Construction
Issue number5
Publication statusPublished - 1 Sept 2010


  • Bonding
  • Concrete beams
  • Fiber reinforced polymers
  • Finite element method
  • Shear failure
  • Shear resistance
  • Strain distribution
  • Stress distribution

ASJC Scopus subject areas

  • Civil and Structural Engineering
  • Building and Construction
  • Ceramics and Composites
  • Mechanical Engineering
  • Mechanics of Materials


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