1622Properties of FRP Reinforcing Bars

Glass fiber reinforced vinylester bars are the most commonly commercially produced FRP rebars. They are available from a number of manufacturers. Bars are typically produced in sizes ranging from | in. to 1 in. in diameter (i.e., #3 to #8 bars). Bars have a sand coated external layer, a molded deformation layer, or a spiral wind layer to create a nonsmooth surface.

The properties of FRP rebars are reported by manufacturers in accordance with ACI 440.1R-03 recommendations for guaranteed tensile strength and longitudinal modulus. It is important to note that the reported strength of FRP rebars decreases with the diameter of the bar. This is attributed to the relatively low in-plane shear strength of the FRP rebars. Designers need to consult manufacturers' recommended properties to be used for design. Typical properties are shown in Table 16.4 for glass fiber FRP rebars and carbon fiber FRP bars. It should be noted that the carbon fiber bars are typically used as prestressing tendons or "near-surface-mounted" (NSM) strengthening and not as conventional reinforcing bars due to cost considerations.

FRP rebars are considered to be transversely isotropic from a mechanics perspective (Bank 1993). Theoretical equations are available to predict the mechanical and physical properties of the FRP rebars from the properties of the fiber and resin constituents. Theoretical methods are not available to predict the bond properties and the long-term durability characteristics of FRP rebars. A specification has been

TABLE 16.4 Properties of Typical Commercially Produced FRP Reinforcing Bars
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