FRP Stay-in-Place Formwork for Seismic Resistant High-Strength Concrete Columns


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Title: FRP Stay-in-Place Formwork for Seismic Resistant High-Strength Concrete Columns

Author(s): T. Ozbakkaloglu and M. Saatcioglu

Publication: Special Publication

Volume: 230


Appears on pages(s): 1593-1612

Keywords: column deformability; columns; concrete confinement;earthquakes; fiber reinforced polymer (FRP); high-strength concrete(HSC)

Date: 10/1/2005

Fiber reinforced polymer (FRP) casings, in the form of stay-in-placeformwork, provide an attractive alternative to conventional confinement reinforcementfor concrete columns. These casings can fulfill multiple functions of; i) formwork, ii)confinement reinforcement, and iii) protective shell against corrosion, weathering andchemical attacks. This paper investigates the use of stay-in-place FRP formwork asconcrete confinement reinforcement for HSC columns with circular and square cross-sections. Large-scale specimens with 270 mm cross-sectional dimension and up to 90MPa concrete strength, were tested under combined axial compression andincrementally increasing lateral deformation reversals. FRP casings were manufacturedfrom carbon fiber sheets and epoxy resin. One of the square columns was providedwith internal FRP crossties, a new technique introduced by the authors, to provide well-distributed lateral restraints along the column face, thereby improving the mechanismof confinement. The results indicate that the deformation capacity of HSC columns canbe improved significantly by using FRP casings. The results further indicate that theconfinement effectiveness of casings of square columns is significantly affected by thecorner radius of casings. Confinement efficiency of these casings improves with the useof FRP crossties.