TY - GEN
T1 - Quantifying strain variation in FRP confined concrete using digital image correlation
T2 - 1st Asia-Pacific Conference on FRP in Structures, APFIS 2007
AU - Bisby, L.
AU - Take, W. A.
AU - Caspary, A.
N1 - Funding Information:
The Authors would like to acknowledge the financial support of Queen's University, the Natural Sciences and Engineering Research Council of Canada, and the Intelligent Sensing for Innovative Structures Network (ISIS Canada) of the Networks of Centres of Excellence Program of the Government of Canada. The Authors would also like to thank Mr. Jeff Kemp for his assistance in performing the tests described herein.
Publisher Copyright:
© 2007 International Institute for FRP in Construction
PY - 2007
Y1 - 2007
N2 - 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.
AB - 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.
KW - Confinement
KW - FRP
KW - Image correlation
KW - Reinforced concrete columns
KW - Strain efficiency
KW - Strengthening
UR - http://www.scopus.com/inward/record.url?scp=85082693234&partnerID=8YFLogxK
UR - https://www.civil.hku.hk/apfis07/
UR - https://www.iifc.org/publications-resources/proceedings/
M3 - Conference contribution
AN - SCOPUS:85082693234
T3 - Proceedings of the 1st Asia-Pacific Conference on FRP in Structures, APFIS 2007
SP - 599
EP - 604
BT - Proceedings of the 1st Asia-Pacific Conference on FRP in Structures, APFIS 2007
A2 - Smith, Scott T.
PB - International Institute for FRP in Construction (IIFC)
Y2 - 12 December 2007 through 14 December 2007
ER -