Semester

Fall

Date of Graduation

2004

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Civil and Environmental Engineering

Committee Chair

P. V. Vijay

Committee Co-Chair

Hota GangaRao.

Abstract

In this research, increases in strength, stiffness and ductility due to external wrapping of Carbon Fiber Reinforced Polymer (CFRP) sheets on plain and steel reinforced concrete cylinders were studied. The research focused on behavior of plain and wrapped concrete cylinders with respect to parameters such as: (1) concrete compressive strength (fc'); (2) fiber orientation of CFRP wrap (0°, 45° and +/-45°); (3) cylinder size (3" x 6", 4" x 8", 6" x 12"); (4) number of CFRP wraps (1, 3, 6); (5) wrapping height and location (top and bottom, middle); (6) degree of fabric wetting; and (7) degree of bonding fabric onto concrete. The mechanical properties evaluated include confinement related increase in axial strength/stiffness, energy absorption (deformability factor), and failure modes. The experimental results were correlated to analytical models consisting of terms representing lateral confining/radial pressure generated by the wrap in hoop direction.;The mechanical properties were compared to those of non-wrapped specimens. An increase in strength of 1.5--3 times and hoop strain of 10--20 times was noticed. The increase in axial strength of 3" x 6" concrete cylinder per layer of wrap for 1, 3 and 6 layer wrapped cylinder was 29%, 43.7% and 33.93%, respectively. Cylinders completely bonded with wrap showed 1.52 times increase in strength whereas cylinders with 31.8% and 21.2% bond showed 1.48 times and 1.23 times increase in strength, respectively. Thus the small delaminations or discontinuities in bonding that may be caused during hand or machine wrapping of column specimens are not critical and do not affect the confinement related strength increase. Deformability factor or energy absorption of specimen wrapped with 3 wraps of 0° fiber direction showed 12 times increase and specimens with +/-45° wrap showed 9 times increase compared to non-wrapped specimens.;Aging of wrapped and non-wrapped cylinders with and without internal steel reinforcement and carbon strip specimens was studied by subjecting them to elevated temperature (175°F) and freeze-thaw (-20°F to 120°F) condition. Wrapped cylinders showed a maximum decrease in strength of 12% in elevated temperature aging and 5% in freeze thaw aging. Further Aging is underway for both conditions.;Non-destructive infrared thermography tests were done to study the interfacial bond between concrete and wrap. Thermograms were recorded to identify the presence of localized delaminations in the wrapped specimens. Infrared thermography was also used to examine delamination size increase in aged specimens, and no detectable growth was observed with thermography.

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