Literature Survey on Shear in FRC Beams - On Shear Behavior of Structural Elements Made of Steel Fiber Reinforced Concrete - page 38

3.11.8 Effect of Longitudinal Ratio

The main effect of longitudinal reinforcement ratio ( ) is on beam ductility [ 6 ].

Flexural yielding was observed in several beams tested by Dinh et al. [ 6 ] with a
longitudinal reinforcement ratio of approximately 2 %, whereas no yielding
occurred in any of the beams with a reinforcement ratio greater than 2 %. For beams
with a 2 % longitudinal reinforcement ratio, the shear strength of beams with a
0.75 % ber volume fraction (prior to flexural yielding) was believed to be close to
the shear demand associated with

ˁ

exural yielding [ 6 ].
Imam et al. [ 41 ] ensured that the increase of

fl

ˁ , increases the shear and the

fl exural strength, but the increase of the latest one is higher.

Longitudinal reinforcement affects beam shear strength by in uencing the size of

the compression zone and by providing shear resistance through dowel action by
enhancing the tensile strength of the concrete in the splitting plane along the bars
[ 6 , 7 ]. Depending on the amount of steel reinforcement used,

fl

fl exural yielding

might develop rst, followed by shear failure of the beam [ 6 ].

3.11.9 In fl uence of Prestressing

Furlan and Bento-de-Hanai [ 34 ] ensured that shear strength is increased more due
to the prestressing than due to the

bers. Other effect of prestressing is that it
decreases the slope of the compression struts and increases the extent of the non-
cracked area [ 34 ].

3.11.10 In fl uence of Concrete Strength

Narayanan ensured that, for the same ber factor, the shear strength increases with

cube strength [ 7 ].
Tiberti et al. [ 95 ]af rmed that the use of High Strength Concrete reduces the

crack spacing with respect to the Normal Strength Concrete.

3.12 Fibers Influence on Deflections

Fibers make possible smaller de fl ections [ 22 , 28 , 34 ], in fact, de fl ections can be

visible before collapse [ 5 , 11 , 17 , 32 ]; these de ections are reduced because of

increased stiffness [ 41 , 65 ] so deformation characteristics are improved [ 21 , 72 ]. On
the other hand, if

fl

bers acted compositely with stirrups, larger de fl ections are

observed [ 21 , 28 ].