Literature Survey on Shear in FRC Beams - On Shear Behavior of Structural Elements Made of Steel Fiber Reinforced Concrete - page 22

3.4.3 Fibers Partially Replacing Stirrups

Shear reinforcement can be substituted partially or totally with steel bers [ 15 , 53 ].

Anyway, the use of ber reinforcement can reduce the amount of shear stirrups

required [ 9 , 10 ], even though this substitution may not be attractive from a practical
point of view.

3.4.4 Shear Crack Pattern in FRC Elements

The pattern of cracks developed in FRC beams subjected to shear was similar to
those observed in reinforced concrete beams with minimum amount of stirrups [ 7 ],
when FRC satis

es the minimum performance requirements [ 57 ], reaching the

maximum fl exure capacity [ 59 ]; therefore, bers represent an effective shear rein-

forcement [ 28 ].

3.5 Failures Modes

3.5.1 Can Fibers Alter the Collapse from Shear to Flexure?

The inclusion of bers can modify the brittle shear mechanism into a ductile

fl exural mechanism, thus allowing a larger dissipation of energy [ 39 ] and a sig-

ni cant increase of ductility and load-bearing capacity [ 11 , 53 ]. Therefore cata-

strophic failures are avoided when using FRC.
This change of shear failure due to

bers was analyzed by different authors

[ 7 , 11 , 25 , 28 , 39 , 53 , 57 , 60 , 61 ].
Some authors assert this change in failure mode type, depending on the ber

content:
Normal-strength concrete beams changed the failure mode form shear to exure

with a volume fraction of 2 % of bers, while high-strength concrete beams were
subjected to a bending failure (no shear failure) with a volume fraction of about
1.5 % of

fl

bers. Furthermore, normal-strength concrete involved a large increase of
shear resistance up to 1 % of

bers, whereas most increase occurred at 0.5 % of

bers in high-strength concrete [ 62 ]. However, as mentioned above, the key-

parameter is FRC performance expressed in terms of post-cracking residual

strength.
Narayanan and Darwish [ 7 ] and, Lim and Oh [ 9 , 10 ] ensured that beyond an
amount of 1 % the mode of failure change from shear to

exure, but Narayanan
highlighted that beyond a volume fraction of 1 % the improvement on shear
strength is very little. By contrast, according to some authors, due to the high

fl