Introduction - On Shear Behavior of Structural Elements Made of Steel Fiber Reinforced Concrete - page 5

considering FRC as a composite with enhanced toughness, the ber effects are

included as a concrete contribution. This was done to obtain a more representative
modeling of the actual effect of

bers, which basically make the concrete matrix
tougher after cracking by improving both the transfer of residual tensile stresses and
the aggregate interlock (the latter, by keeping cracks smaller). However, it should
be noted that the two formulations require toughness properties. When combining

bers with stirrups, both Codes include an additional term to consider the effect of
stirrups. The proposed model and the RILEM formulation were compared with of a
wide experimental database. Although the

t is less promising when dealing with
high strength concrete specimens or prestressed members, the RILEM results are
slightly more re ned for small-sized elements than for deep beams.

The ACI 318-11 Code [ 18 ] does not include a formula to calculate the shear
strength of SFRC beams and only assumes a minimum shear strength which

bers

can withstand. In 2006, Parra-Montesinos [ 19 ] ensured that hooked steel bers in

an FRC with a 0.75 % by volume fraction of steel bers can be used in lieu of

minimum stirrup reinforcement in beams. A limit based on FRC toughness prop-
erties (that does not only depend on the amount of bers) would be a better criterion

to justify substitution of transverse reinforcement.
Other countries have produced design guidelines, including: France (AFGC-
SETRA, 2002), Sweden (St

ä

berbeton, 1995), Germany (DAfStb, 2007), Austria
(Richtlinie Faserbeton, 2002), Italy (CNR, 2006) and Spain (EHE: Appendix 14
[ 20 ]) (the latter based on RILEM guidelines [ 15 ]).
The FRC shear design workshop held in Sal ò (Italy) proved to be an interesting
advance in the development of the Model Code provisions [ 16 ] and in inspiring
future research into these topics. Lectures were included in a

l

b Bulletin [ 21 ].

1.3 Contents

This Ph.D. thesis is divided into ve parts:

The Part I: Introduction and Objectives consists of Chaps. 1 and 2

￿ Chapter 1 is an introduction to the shear behavior of concrete structural ele-

ments, with and without bers, with a brief historical review on the research to

date on this topic. Also included are the main topics in papers related to FRC
elements subjected to shear and the benets on shear behavior of the addition of
steel contribution to shear.

Finally, there is a brief summary of the contents of this Ph.D. thesis.

bers. Current Codes are cited that include bers '

Chapter 2 describes the objectives pursued in this thesis and its contribution to
the research in its

￿

eld.

Part II: State of the Art describes the state-of-the-art of the shear behavior of
structural concrete elements made with ber reinforced concrete (Chap. 3 ) .