Civil Engineering Reference
In-Depth Information
Table 8.14
(continued)
Parameter
Neither
bers
nor stirrups
Beams only with
stirrups
Beams only
with
bers
Beams with
bers and
stirrups
˃
c
(MPa)
MC2010:
Underestimates
the effect of
prestressing.
EHE08,
MC2010 and
RILEM: SM
increase linearly
with
EHE08, MC2010
and RILEM: All
prestressed beams
are safe (SM > 1)
EHE08 and RILEM
are most balanced
for all levels of f
c
and
˃
c
whereas
MC2010 is always
the most
conservative
For reinforced
beams EHE08
is the most
conservative
while, for pre-
stressed is the
RILEM
MC2010 is the
most balanced
(similar SM for
reinforced and
prestressed)
c
and,
prestressed
beams are
always safe
˃
A
sa
/s (cm
2
/m)
-
-
-
-
:Noin
fl
uence have been detected
-
8.7 Particular Cases
8.7.1 Introduction
Throughout this chapter, the role of the factors in
uencing shear strength in the
safety margin (SM) in three design Codes (EHE, MC2010 and RILEM) have been
analyzed in different cases: beams without any shear reinforcement, beams with
only stirrups, beams with only steel
fl
bers and
nally, beams with stirrups and
bers.
At this point, in which the in
uence of the different factors on the SM is
reported, it is presented the possible in
fl
uence of the interactions of different factors
on the SM. For this purpose, the analysis of variance
fl
“
ANOVA
”
will be used.
ANOVA makes the following assumptions:
Independence of cases. This is an assumption of the model that simpli
es the
statistical analysis.
Normality. The distributions of the residuals are normal.
Equality (or
) of variances, called homoscedasticity. The vari-
ance of data in groups should be the same.
“
homogeneity
”
uence of an independent variable
(factor) in the dependent variable, in this case, SM. The two-way analysis of
variance is an extension to the one-way analysis since there are two independent
variables (hence the name two-way).
The one-way ANOVA examines the in
fl
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