Flexural Strengthening of Beams and Slabs - Strengthening Design of Reinforced Concrete with FRP - page 92

B ≈ 2

a
d f

=− − 110.4404 = 0.252

a = 4.46 in c5.57in =

0.003 16.25 5.57
5.57

−

ε= = 0.0057 > 0.005 ductile crushing

s

0.003 17.69
5.57

×

ε= − 0.003 = 0.00652

f

ε=ε−ε= 0.00652 <ε =ε=× × 0.7 .7 0.95 0.0167 = 0.0111

fe f bi fd fu

f fe = 18,000 × 0.00652 = 117.36 ksi

f
f

f
f

a
d

5
117.36

4.46
16.25

83.5
117.36

c y

ρ= 0.85 −ρ = 0.85 × × − 0.01083 × = 0.00223 f s

fe fe

0.363 in 2 A d =ρ = 0.00223 × 10 × 16.25 = f f

2

A = 0.63 × 0.079 = 0.0498 in strip

A f

#ofstrips = = 7.3strips

A

strip

Use eight strips in four grooves with 2-in. spacing between the grooves. According
to ACI 440.2R-08, Figure 13.4, the groove dimensions are 3 × 2 × 0.079 = 0.474" by
1.5 × 0.63 = 0.95". However, the same number of CFRP strips was successfully used in
a beam with cut grooves of 0.25" × 0.75", as seen in Figure 5.7 (Rasheed et al. 2010).

CFRP strips
(1 per groove)

18 in.

CFRP strips
(2 per groove)

2 in.
10 in.

FIGURE 5.7 Example 5.5 showing the CFRP NSM design details.