Civil Engineering Reference
In-Depth Information
For structural use, the designer has to specify the residual strength class (f
R1k
)
and the ratio (f
R3k
/f
R1k
). Fiber reinforcement can substitute (also partially) con-
ventional reinforcement (rebars) at ULS, if the following relationships are ful
lled:
f
R1k
=
f
Lk
[
0
:
4
ð
3
:
2
Þ
f
R3k
=
f
R1k
[
0
:
5
:
ð
3
:
3
Þ
3.2.3 Constitutive Laws
For the post-cracking behavior of FRC, a stress-crack opening law in uniaxial
tension is de
ned. The rigid-plastic model takes the static equivalence into account
(Fig.
3.5
), where f
Ftu
results from the assumption that the whole compressive force
is concentrated in the top
ber of the section:
ed stress-crack opening constitutive laws may be deduced from the
bending test results: a plastic rigid behavior, or a linear post-cracking behavior
(hardening or softening), Fig.
3.6
, where f
Fts
represents the residual strength
Two simpli
f
bh
2
f
bh
2
R
3
sp
Ftu
sp
M
=
=
u
6
2
f =f /3
R3
f
R3
Ftu
Fig. 3.5 Simplied model adopted to compute the ultimate tensile strength in uniaxial tension f
Ftu
by means of the residual nominal bending strength f
R3
[
2
]
(a)
(b)
rigid-plastic
f
Ftu
post- crack
hardening
f
Ftu
f
Fts
f
Ftu
post- crack
softening
f
Ftu
w
u
w
u
w
w
Fig. 3.6 Simplied post-cracking constitutive laws: stress-crack opening (continuous and dashed
lines refer to softening and hardening post-cracking behavior respectively) [
2
]
Search WWH ::
Custom Search