Shear Database and Study of the Parameters Influencing Shear Behavior - On Shear Behavior of Structural Elements Made of Steel Fiber Reinforced Concrete - page 185

By means of the surface charts, it can be observed that MC2010 is the safest; it
only gives the lower results (SM around the unit) when using long bers (50 mm).

When bers are long and shortly slender (45/50BN), MC2010 gives results slightly

unsafe for both levels of compressive strength. When bers are long and very

slender (80/50BN), SM is low in high strength concrete.
RILEM is the most unconservative Code, followed by the EHE08. For this
Series SM are always greater than the unit for beams of medium compressive
strength and

bers 80/50BN.
When Codes gives SM < 1, it means that they estimate theoretical shear values
too high; in this case, it seems that Codes are overestimating the effect of bers. 45/

50BN are bers longer and less slender than the other types of bers used; there-

fore, for the same amount of steel, less bers are into the concrete. This fact,

coupled with high compressive strength, results in a brittle matrix and, in this case,
Codes should be more conservative.

8.8 Conclusions According to the Analyzed Shear Database

After analyzing a shear database consisting of 215 structural elements, it was
detected the influence of each parameter influencing shear.
In the following, Codes will be compared with the experimental results available
in the considered database, under the assumption that the partial safety factors are
equal to the unit; therefore, the comparisons will not refer to the safety because, in
this case, this safety factor have to be considered.

8.8.1 In fl uence of Effective Depth, d

For effective depth (d) of about 200 mm, Codes were always conservative for all
cases except for beams with only stirrups (see square in solid line, Fig. 8.42 ).
When d ≥ 900 mm, in beams without any shear reinforcement (neither stirrups

nor bers), the analyzed Codes underestimate the shear strength; on the contrary, in

beams with stirrups, Codes were too conservative. In beams with only bers as

shear reinforcement, Codes give intermediate results (see square in dashed line,
Fig. 8.42 ). So when stirrups are not present, Codes underestimate the shear strength
for d

900 mm.
It should be underlined that both, stirrups and

≥

bers, can mitigate size effect in

shear (Fig. 8.43 ).