Literature Survey on Shear in FRC Beams - On Shear Behavior of Structural Elements Made of Steel Fiber Reinforced Concrete - page 21

3.4 Steel Fibers as Shear Reinforcement

In the literature, it is shown that FRC can substitute, at least partially, transverse
reinforcement. For this reason, some authors emphasize the usefulness of bers for

industrial applications.

3.4.1 Fibers as Minimum Shear Reinforcement

The minimum transverse reinforcement requirement can be met by using bers in

suf cient amount and with minimum performance in terms of toughness [ 3 , 32 , 50 ].

Fibers can replace the minimum amount of transverse reinforcement satisfying
the minimum shear reinforcement criteria in ACI 318-11 [ 32 , 51 , 52 ] and other
Codes for precast high performance concrete structures [ 53 ].
According to ACI 318-11 [ 52 ], a minimum V f of 0.75 % is recommended
[ 6 , 54 ]. On the other hand, the beams reinforced only with steel bers (V f = 0.64 %)

show a similar, or even better, post-cracking behavior than the beams with the
minimum amount of transverse reinforcement [ 27 ].
According to the

b Model Code 2010 [ 2 ], it is possible to prevent the use of the
minimum amount of conventional shear reinforcement (stirrups) if the following
condition is ful lled:

p

f ck

f Ftuk ð 3 : 8 Þ

20

where f Ftuk (MPa) is the characteristic value of the ultimate residual tensile strength
for FRC, by considering w u = 1.5 mm. This allows limiting the development and
the diffusion of the inclined cracking and, as a consequence, can ensure suf cient

member ductility.

3.4.2 Fibers Totally Replacing Stirrups

Fibers clearly acted as shear reinforcement [ 19 , 28 , 55 , 56 ] and they can be used to
replace stirrups in beams without reduction of the moment capacity [ 57 ]; in precast
pretensioned beams [ 58 ], the use of FRC can signi

cantly reduce production costs
[ 27 ] since handling and placing of reinforcement [ 53 ] are no longer required.
From a practical point of view, steel

bers can successfully replace the shear
reinforcement, but it is senseless to use steel bers as a complementary rein-

forcement of longitudinal bars [ 55 ].