Concrete Confinement Using Carbon Fiber Reinforced Polymer Grid


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Title: Concrete Confinement Using Carbon Fiber Reinforced Polymer Grid

Author(s): A.P. Michael, H.R. Hamilton III, and M.H. Ansley

Publication: Special Publication

Volume: 230


Appears on pages(s): 991-1010

Keywords: concrete; concrete strength; confinement; ductility; FRP materials; grid

Date: 10/1/2005

Corrosion of prestressing steel in precast concrete is a significant problemfor coastal bridges in Florida. Replacement of prestressing steel with carbon fiber-reinforced polymer (CFRP) reinforcement provides a potential solution to this costlyproblem. The Florida Department of Transportation (FDOT) structures research centerhas teamed with the University of Florida (UF) to evaluate CFRP reinforced piles thatemploy two types of carbon reinforcement: (a) CFRP reinforcing bars and (b) CFRP grid.The CFRP bars act as flexural reinforcement while the CFRP grid provides confinement tothe concrete core. The focus of this paper is on the confinement provided by theembedded CFRP grid, which is tied into a circular shape and cast into the concrete in asimilar configuration to spiral ties. Existing confinement models are based onconfinement provided by FRP wraps. Consequently, their use in predicting confinementmust be validated with tests on embedded FRP grid. Standard (152 mm x 304 mm)concrete cylinders were cast both with and without the embedded CFRP grid. Thecylinders were tested in compression to determine the effect of the CFRP grid on theirstrength and ductility. A significant improvement in ductility was observed for thecylinders with the embedded CFRP grid compared to the control cylinders.