Debonding of FRP EBR: from testing to design

A recent survey showed that many different experimental set-ups have been used for determining the FRP-to-concrete bond strength, but no consensus on a standard test procedure has been reached. The authors (Yao et al. 2005) classified the existing test setups into the following five types: (a) double-shear pull tests; (b) doubleshear push tests; (c) single-shear pull tests; (d) single-shear push tests; and (e) beam (or bending) tests.
Such a method must be simple and convenient so that sufficient numbers of replicate specimens can be constructed and tested. Furthermore, the test method must produce easily interpreted results so that it will be accepted by the design community, construction industry, and owners.

Collectively, all these four tests may also be referred to as pull tests, as the plate is always directly pulled by a tensile force. The far end supported double-shear pull tests (a) and near-end supported single-shear pull tests have been the most popular test methods so far due to their simplicity. Such methods are useful in capturing the fracture energy and may ultimately provide better models of the debonding process. The double shear test provides a symmetric test specimen that is loaded uniaxially.
Specimen construction tolerances, however, are such that it is difficult to avoid eccentricity in the FRP composites. Pellegrino et al. (2008) have tested several specimens using double-shear pull test method with the aims to better understand FRP – concrete bond behavior .

The En-Core European research network, together with the fib (International Federation of Concrete) TG 9.3 have planned round robin tests (RRT) for FRP reinforcement in order to assess the properties of FRP materials for reinforcing and strengthening concrete structures. The proposed set-up consists in a double shear test. Yao et al. (2005) and Ceroni, Pecce (2010) have tested the specimens using near – end supported single-shear test. Ceroni and Pecce (2010) in some specimen have added anchoring devices to understand the behavior.