Quantifying strain variation in FRP confined concrete using digital image correlation: Proof-of-concept and initial results

L. Bisby*, W. A. Take, A. Caspary

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract / Description of output

Circumferential (hoop) wrapping with externally bonded (EB) fibre reinforced polymer (FRP) sheets is now a method of choice for strengthening and axial deformability enhancement of reinforced concrete columns. The mechanics of FRP confinement and the development of predictive models for axial strength and strain enhancement have received significant research attention over the past two decades, such that design codes and guidelines for these types of members are now available. However, one fundamentally important factor that remains incompletely understood is the Strain Efficiency of the FRP wraps - the ratio of the tensile hoop strain in EB FRP wraps at failure (member failure is typically initiated by hoop failure of the FRP wraps in tension) to the failure strain observed in tensile tests on FRP coupons. Research on these types of members using conventional instrumentation (i.e., discrete foil strain gauges) has shown that the measured hoop strain at failure may lie anywhere in the range of 50% to 110% of coupon test values, although typically it is considerably less than 100%. These limited data provide little insight, however, into the variation of hoop strain over the surface of FRP wraps, the factors influencing Strain Efficiency, or even whether the true failure strains are accurately captured by localized conventional strain instrumentation. This paper presents the initial results of a study aimed at quantifying the axial and hoop strain variation over the surface of FRP confined concrete cylinders using a novel digital image correlation technique. Included are a proof of concept for the new technique, initial results, and comparisons with data obtained using conventional instrumentation. Implications for future testing and a more complete understanding of FRP confined concrete are discussed.

Original languageEnglish
Title of host publicationProceedings of the 1st Asia-Pacific Conference on FRP in Structures, APFIS 2007
EditorsScott T. Smith
PublisherInternational Institute for FRP in Construction (IIFC)
Pages599-604
Number of pages6
ISBN (Electronic)9789628014149
Publication statusPublished - 2007
Event1st Asia-Pacific Conference on FRP in Structures, APFIS 2007 - Hong Kong, China
Duration: 12 Dec 200714 Dec 2007

Publication series

NameProceedings of the 1st Asia-Pacific Conference on FRP in Structures, APFIS 2007
Volume2

Conference

Conference1st Asia-Pacific Conference on FRP in Structures, APFIS 2007
Country/TerritoryChina
CityHong Kong
Period12/12/0714/12/07

Keywords / Materials (for Non-textual outputs)

  • Confinement
  • FRP
  • Image correlation
  • Reinforced concrete columns
  • Strain efficiency
  • Strengthening

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