Literature Survey on Shear in FRC Beams - On Shear Behavior of Structural Elements Made of Steel Fiber Reinforced Concrete - page 17

strength is relatively small. Majdzadeh et al. [ 13 ]af rmed that a volume of 1 % is

optimal and no bene ts are detected with volumes beyond 1 % [ 13 ]. By contrast,

Oh et al. [ 10 ] ensured that the increase was approximately 100 % form volumes
between 0 and 2 %.
Furthermore,

ber reinforcement enhanced the shear capacity of RC beams, but a

ber volume fraction of 1 % is seen as optimal; in fact, no bene ts were noted when

the ber volume fraction was increase beyond 1 % [ 13 ]. The increase of the shear

strength was about 100%when the

ber content was increased from 0 to 2 % [ 10 ]; the

use of hooked steel bers in a volume fraction greater than 0.75 % led to an enhanced

inclined cracking pattern (multiple cracks) and improved shear strength in beams
(without stirrup reinforcement), of 0.33 · √ f c (MPa). The increase in shear strength

was associated with an increase in ber content beyond 1 % by volume, however, it

was relatively small [ 6 ]; the maximum increase of shear strength at

rst crack in fully

prestressed beams due to the addition of bers was 5, 10 and 20 % for the volume

fraction of ber of 0.5, 1.0, and 1.5 %, respectively. In the case of partially prestressed

beam specimens, the increase of peak load due to addition of bers was found to be 12

and 17.5 % for partially prestressed beams with ber content of 1.0 and 1.5 %,

respectively [ 14 ]. The addition of ber reinforcement in full depth for partially pre-

stressed concrete beams improved the shear-resisting capacity by approximately
11 bers.

The maximum benet due to the addition of bers was observed for high-strength
prestressed concrete beams. The increase in the shear capacity due to the presence of

- 20 %when compared with the corresponding control beams not containing

ber reinforcement only in the web portion, when compared with the control beams,
was found to be 6, 9, and 14 % for normal, moderately high strength, and high
strength concrete beams, respectively. Hence, the addition of bers only in the web

portion of the T-beam is recommended for enhancing the shear capacity of the
prestressed concrete beam [ 15 ].
As far as the beam stiffness is concerned, the presence of

ber reinforcement
delays and controls dowel cracking and, thereby, improves the stiffness and
deformation characteristics of the dowel crack zone. The rst shear-crack load

forms and ultimate dowel strength are both found to increase almost linearly with
the

bers in concrete deep
beams resulted in enhanced stiffness and increased spall resistance at all stages of
loading up to failure;

fl exural strength of the composite. The inclusion of steel

bers also reduced crack width [ 16 ].

3.3.3 Effect of Fibers on Ductility (Postcracking Response)

Fibers increase ductility in FRC beams versus beams without bers [ 4 , 7 , 14 , 17 - 23 ];

also, the increase in ductility of concrete in compression is due to ber addition

depends, among other factors: amount, geometry, orientation, strength of the steel

bers, bond between bers and concrete [ 24 ] and post-cracking strength because of

bers addition [ 8 , 18 , 19 , 25 , 26 ]. In order to get a ductile post-peak behavior, bers

having a higher aspect ratio are required [ 20 ].