Civil Engineering Reference
In-Depth Information
Fig. 3.7 Influence of L
r
on
the flexural behavior of SFRC
beam [
49
]
12
Lr=h/4
Lr=h/2
11
Lr=h
10
Lr=2h
9
8
7
6
0
0.25
0.50
0.75
1
w (mm)
signi
cant for serviceability crack openings and f
Ftu
represents the residual strength
signi
cant for ULS when assuming the rigid-plastic behavior (Fig.
3.7
a), f
Ftu
equal
to f
R3
/3.
The stress-strain law is based on the identi
cation of the crack width and on the
corresponding structural characteristic length,
l
cs
, of the structural element for
softening materials. The strain can be assumed as:
e ¼
w
=
l
cs
ð
3
:
4
Þ
And, in elements with conventional reinforcement (rebars),
l
cs
, as:
l
cs
¼
min s
rm
;
f
y
g
ð
3
:
5
Þ
where:
s
rm
: mean distance value between cracks;
y
: distance between the neutral axis
and the tensile side of the cross section, evaluated in the elastic cracked phase by
neglecting the residual tensile strength of FRC, and for a load con
guration cor-
responding to the serviceability state of crack opening and crack spacing.
3.2.4 Partial Safety Factors
Design values for the post-cracking strength parameter at ULS, according to the
MC2010 [
2
], can be determined as:
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