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Fig. 1.4.1 Stress-strain curves for plain (unconfined) and FRP-confined concrete.

For rectangular cross sections with dimensions b and h (b>=h), Fig. 1.4.2, the

effect of FRP confinement may be calculated based on the following

expressions for the confined concrete strength fcc and the corresponding strain

cu:

Fig. 1.4.2 Rectangular cross section with radius R at corners.

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(1.4.1)

(1.4.2)

where

(1.4.3)

(1.4.4)

(1.4.5)

(1.4.6)

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(1.4.7)

(1.4.8)

(confinement effectiveness

coefficient) (1.4.9)

Eco = initial elastic modulus of concrete, co = 0.002 (strain corresponding to f

co), Ag = gross sectional area of concrete = bh-(4-)R2.

Note that for circular cross sections of diametre D confined with strips of

width bfat a spacing sf, ke is given as follows:

(1.4.10)