Civil Engineering Reference
In-Depth Information
4.4.4 Shear Values Calculated with the Current
Design Codes
Shear strength capacities were calculated from current Codes EHE08 [
6
], EC2 [
7
]
and the
nal draft of MC2010 [
8
]. The formulations are shown in Introduction to
Part III.
It is important to clarify that the
rst complete draft of the Model Code was used
as it was the latest version available when the results were analyzed. On the other
hand, as EC2 has no formulation which includes the
ber contribution, it was
calculated by following the RILEM approach [
9
].
The notation (see Introduction to Part III) and formulas were adapted to facil-
itate comparisons and have the following general structure:
V
u2
¼
ð
V
cu
þ
V
fu
Þ þ
V
su
ð
4
:
2
Þ
All the Codes consider the contribution of the traditional transverse reinforce-
ment (V
su
) in the same way and are evaluated according to the following
expression:
V
su
¼
z
sen
a
ð
cotg
a þ
cotg
h
Þ R
A
a
fy
a;
k
ð
4
:
3
Þ
No Code considers the explicit in
fl
uence of crack inclination on the evaluation of
the
ber contribution or proposes a
ber effect on the
ʸ
value considered in the
shear reinforcement contribution (V
su
). The
bers are therefore considered sepa-
rately from stirrups.
The theoretical shear strength values were calculated by the following criteria
(for each Code):
MC2010: Beam H600TR/3 (without
bers) was calculated by applying the most
accurate form (Level III of Approximation), which permits the calculation of
-
x
and directly calculates the corresponding inclination of the compression stresses
(
ʵ
). Level III of Approximation was based directly on the equations of the
Modi
ʸ
bers)
were calculated by applying the formula proposed in MC2010, which includes
the effect of
ed Compression Field Theory (MCFT) [
10
]. Other beams (with
bers inside the concrete matrix contribution.
EHE08: This reference angle of cracks inclination (
ʸ
e) was taken to be equal to
-
the inclination of compression stresses (
) calculated according to the general
method of the EHE (analogous to the MCFT):
ʸ
ʸ
=
ʸ
e.
EC2: When considering shear in beams with stirrups, EC2 neglects the concrete
contribution to shear (Vcu). Several authors, including the EC2, have doubts
about the concrete contribution to shear when stirrups are needed. Cladera and
Mar
-
[
11
,
12
] concluded that the EC2 procedure is very easy to use but its results
are very scattered. On the one hand, it may be too conservative for slightly
shear-reinforced beams or for prestressed beams; and on the other it may prove
slightly underestimated for heavily reinforced members. For the EC2,
í
ʸ
value
Search WWH ::
Custom Search