Shear Strengthening of Concrete Members - Strengthening Design of Reinforced Concrete with FRP - page 153

(a) Completely wrapped column (b) U-Wrapping of interior beam

(c) U-Wrapping of spandral beam (d) Side bonding of AASHTO girder

FIGURE 6.1 Wrapping schemes for FRP shear strengthening.

encasing the member with FRP is discouraged due to the potential prevention of
migration of moisture as well as the more difficult detection of potential localized
delaminations. The second case of installing discrete strips is the more widely used
technique, in which the center-to-center distance between strips depends on the
amount of FRP needed, which translates into the total number of strip layers and
the width of each strip. The wider the strips and the fewer the number of layers used,
the more efficient the shear strengthening scheme is, since the interface shear stress
transfer to concrete is lower, which makes the failure mode of sheet debonding less
likely to take place.

6.3 ULTIMATE AND NOMINAL SHEAR STRENGTH
The design shear strength of the member having FRP shear strengthening should
exceed the required shear or the demanded shear value.

φ≥ VV

n

(6.1)

u

The stren gt h reduction factor φ is as per ACI 318-05 (2005). The load factors used to
compute V u are also per ACI 318-05, as specified by ACI 440.2R-08. These factors
are the same as those of ACI 318-11 (2011).
The nominal shear strength, including the FRP contribution, may be obtained
by adding this FRP contribution to that of concrete and reinforcing steel stirrups as
follows:

φ=φ++Ψ VVVV

n

( ) (6.2)

c s f f