where ni was the number of CFRP grid layers, ngs was the number of grid strands, bg was

the width of the grid strands, tg was the thickness of the grid strands and h was the height

of the cylinder.

 The secant modulus of elasticity of concrete (Ec) was calculated based on existing

empirical expressions (Nawy 2003):

 E = 57.f7 (3-2)

wheref'c was the minimum specified compressive strength of concrete, in psi, at 28 days

and Ec is in ksi.

 To determine the confinement strength (fr) simple pressure vessel mechanics were

used (see Fig. 3-14). The equilibrium condition required the force from the confining

strength be equal to the force in the FRP encasement.

 Carbon grid










fgu teg fgu teg




Figure 3-14. Cylindrical pressure vessel

 The equilibrium condition for the confined cylinder was expressed as follows:

 f,, dg = 2 teg fgu (3-3)