Shear Strengthening of Concrete Members - Strengthening Design of Reinforced Concrete with FRP - page 162

Afd
S

fv fe fv

Ψ= × V 0.85 ff

f

*

ε=ε= × C 0.75 0.01278 = 0.00959 GFRP interior exposure fu E u

2/ 3

37.7
27

k = = 1.25

1

23,300
1315.65

L e = = 45.48 mm

( )

0.58

3

×× × 10

113 −× 2 45.48

113

k = = 0.195

2

1.25 × 0.195 × 45.48

k v = = 0.097 < 0.75

11,900 0.00959

×

− 4

ε=ε= × k 9.30 10 < 0.004 fe v u

Ψ= × ×× ×

2320 15,650 × 0.000930 × 113

ff 0.85 = 3,355.1N = 3.36 kN

50

VVVV =++ψ = 31.73 kN + 3.36 kN = 35.09 kN < V = 41.5kNO.K.

n c s f f exp

The ACI 440 model underestimates the shear capacity with FRP in this case,
which is on the conservative side.

Example 6.5: Analysis

Khalifa and Nanni (2000) tested six reinforced concrete T-beams deficient in
shear and strengthened in shear using CFRP sheets. The control beam was des-
ignated as BT1, and one of the strengthened beams was designated as BT4. This
strengthened beam had no steel stirrups and had transverse CFRP U-wrap strips
of 50-mm width at 125-mm on center extending the entire web height along the
clear span. The geometric and material parameters of the beams are given in
Figure 6.7.

f c = 35 MPa, f y = 470 MPa for ϕ 28-mm bars, and f y = 350 MPa for ϕ 13-mm and
ϕ 10 -mm bars.
CFRP sheet: f fu = 3790 MPa, E f = 228 GPa, t f = 0.165 mm

P/2 /2

380 mm

1070 mm 200 1070 mm

100 mm

2 φ 13

305 mm

2 φ 28

50 mm U-wrap strips at 125 mm c/c

2340 mm

Beam BT4

150 mm

FIGURE 6.7 Example 6.5 showing the beam section and profile.