Shear Database and Study of the Parameters Influencing Shear Behavior - On Shear Behavior of Structural Elements Made of Steel Fiber Reinforced Concrete - page 151

8.4 Case 2: Beams with Stirrups (No Fibers)

8.4.1 Parameters In fl uence on Shear for Beams with Only

Stirrups

Table 8.6 summarizes the ranges of the different parameters used in this case:
beams only reinforced transversally with stirrups, without bers. In this Sect. 8.4 ,

only reinforced beams are analyzed since, in case 2 (beams with stirrups), there is
only one prestressed beam and one element is not representative for the analysis.
With respect to the a/d ratio, safety margins (SM) do not show any trend over the
range studied (2.5 3.5). In the range (400 < d < 900 mm) it is observed that

SM increases with increasing values of the effective depth (d). For beams with
f c > 70 MPa, SM are unconservative; however, since there are two reinforced beams
with f c > 70 MPa, these values are not suf

≤ a/d ≤

cient to ensure this tendency. Referring
to the amount of longitudinal reinforcement ( uence on SM, no trends

are detected; it is only observed an increasing trend in shear stresses with the
increase of

ρ l ) and its in fl

ρ l .
Also in this case, the only prestressed beam reinforced with stirrups is safe
according all the Codes. No clear trends are obtained on the in fl uence of the

transverse reinforcement area (A s ʱ /s) on the shear stress or SM.

8.4.2 General Behavior of Codes for Beams with Only
Stirrups

As shows Table 8.7 , EHE-08 presents the largest dispersion and also the lower 5th
percentile. MC2010 is the Code with less CoV. Anyway, all Codes present low
values of 5th percentile, and this could be indicate that Codes does not give very
safe values for this particular subset, consisting in a sample of beams reinforced
only with stirrups.

Table 8.6 Range of parameters in the shear database of reinforced beams with only stirrups
(N = 22 elements)
Parameter Minimum Maximum Average CoV (%)

d (mm) 220 910 392.72 51.89

a/d 2.50 3.52 2.99 12.85

f cm (MPa) 25.90 85.57 44.57 33.12

f R3 (MPa) - - - -

Amount of bers (kg/m 3 )

- - - -

ρ (%) 0.99 3.84 2.46 44.97

˃ c (MPa)

- - - -

A s ʱ /s (cm 2 /m) 1.40 4.90 2.51 42.98