Civil Engineering Reference
In-Depth Information
3
q
3
d
1
=
3
b
d
V
c
¼
0
:
15
=
a
n
ð
100
q
i
f
cm
Þ
ð
3
:
16
Þ
where: a = shear span; f
cm
= average cylinder compressive strength.
In Eq.
3.11
; only the design value of the yield strength of the stirrups (f
ywd
)is
changed into the average yield strength (f
ywm
), giving:
A
sw
s
0
V
s
¼
:
9
d
f
ywm
ð
3
:
17
Þ
In Eq.
3.14
, the parameter 0.12 was originally derived from the following formula:
d
f
eqk
;
3
0
:
7
=
a
0
:
5
s
fd
¼
ð
3
:
18
Þ
c
c
where:
f
eqk,3
characteristic equivalent
fl
exural tensile strength;
0.5
factor to convert the flexural tensile strength into the axial tensile strength;
0.7
factor to convert the characteristic equivalent
fl
exural tensile strength into
the average equivalent
fl
exural tensile strength;
γ
c
partial safety factor equal to 1.5 to obtain the design value of the shear
resistance
˄
fd
.
exural tensile strength is used, the factor 0.7 may be omitted.
Also the partial safety coef
Since the average
fl
cient (
γ
c
) will be left out in order to get a
“
real ultimate
steel
ber contribution
”
. The Eq.
3.13
results:
d
V
f
¼
k
f
k
1
0
:
5
=
a
f
eqm
;
3
b
d
ð
3
:
19
Þ
Material Parameter: Equivalent or Residual Flexural Tensile Strength
The main material parameters for the design of FRC elements in RILEM guidelines
[
76
] were the equivalent
fl
exural tensile strength f
eq,2
and f
eq,3
. The related strain to
the value f
eq,3
was 10
‰
. These parameters are replaced in the Final Draft [
77
]by
the residual
exural tensile strength is
derived from the contribution of the steel bers to the energy absorption capacity
(area under the load-de
fl
exural tensile strength f
R,i
. The equivalent
fl
fl
ection curve) while the residual
fl
exural tensile strength is
derived from the load at a speci
ed Crack Mouth Opening Displacement (CMOD)
or midspan de
ection (Fig.
3.10
). The value which is used for the ULS is f
Rk,4
(CMOD = 3.5 mm) which is related to the strain of 25
fl
‰
[
51
].
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