Shear Assessment and Strengthening of Reinforced Concrete T-beams with Externally Bonded CFRP Sheets

  • Monika Brindley

Student thesis: Doctoral ThesisPhD


Existing reinforced concrete bridges may be deemed inadequate to carry the ever-increasing traffic loads according to the current codes and standards before they reach the end of their design life. It may therefore be required to either strengthen or replace these structures, which can be costly and causes disruptions to the infrastructure. This work investigates experimentally the possibilities to extend the useful life of existing reinforced concrete slab-on-beam structures deficient in shear by means of structural strengthening with fibre-reinforced polymers (FRP). The experimental campaign involved mechanical testing of ten full-scale T-beam specimens, representative of typical existing slab-on-beam bridges. Two sizes of test specimen were used to investigate the effect of size on the ultimate shear capacity of the beams. The investigated shear-strengthening configurations included externally bonded carbon fibre reinforced polymer (CFRP) sheets in a U-wrap configuration with and without end-anchorage and deep embedded CFRP bars. Unstrengthened control specimens were also tested to provide baseline for comparison. The results from the experimental programme revealed that while the deep embedment strengthening solution provides an increase in shear capacity of up to 50%, the strengthening with CFRP U-wraps results in reduced capacity compared with the underlying control beam. This presents a major implication in terms of safe design predictions of shear capacity of reinforced concrete T-beams strengthened with CFRP sheets as this is the most commonly used shear-strengthening scheme in practice. The study also demonstrated that greater contribution from the externally bonded CFRP U-wraps can be achieved using end-anchorage systems, which delay the debonding of the CFRP. The applicability of current codes of standards and guidelines was studied as well as appropriateness of using advanced numerical methods for assessment of existing reinforced concrete structures. It was found that while the standards used for assessment greatly under-predict the shear capacity, the guidelines for FRP-strengthened beams either under- or over-predict the shear capacity of the tested beams. More accurate predictions are possible using advanced fracture mechanics-based methods for both the unstrengthened as well as the strengthened beams.
Date of Award21 Mar 2018
Original languageEnglish
Awarding Institution
  • University of Bath
SupervisorTim Ibell (Supervisor), Antony Darby (Supervisor) & Mark Evernden (Supervisor)


  • Reinforced Concrete T-beams
  • Shear
  • FRP Strengthening
  • Assessment
  • CFRP sheets
  • Deep Embedment
  • Experimental Testing
  • Numerical Analysis

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