Environmental Engineering Reference
In-Depth Information
b) Alternatively, the deformations according to [33] 8.6.1 (7) may be determined
on the basis of design values. These amount to (see Section 3.2)
Concretes up to C 50/60:
f
cR
¼
f
cm
/
g
C
Concrete grade C 55/67 and higher:
f
cR
¼
f
cm
=ðg
C
g
g
C
¼
(f
ck
þ
8 [MPa])/
0
C
Þ¼ð
f
ck
þ
8
½
MPa
Þ=ðg
C
g
0
C
Þ
Reinforcing steel:
f
yR
¼
f
yk
Prestressing steel:
f
p0.1R
¼
f
p0.1k
Under these conditions, the member cross-sections are to be designed in advance in
such a way that the partial safety factors
g
M
for the design values of the material
strengths are not lower than those of [33] 5.3.3 or according to Table 4.8.
c) If the stress increase in the prestressing steel is taken into account in unbonded
tendons, then the characteristic value
Ds
pk
for the stress increase in the
prestressing steel is determined using the mean values of the material propert-
ies. The formation of cracks or opening joints should be considered here (DIN
1045-1 [33] 8.7.5).
Determining the internal forces with the help of a non-linear method requires
Ds
pk
g
P
according to Table 4.3.
3. Owing to the given strength values, the stress-strain curves for concrete and
reinforcing steel, including tension stiffening, are used (see Section 3.2), or the
bending moment-curvature relationships are developed (see Section 3.3).
4. Determining the critical design load cases from the permanent actions (self-weight
of structure and permanent fitting-out loads) plus the variable actions according to
Section 4.5.3 or 4.6.4.
According to [44] Equation 4.7, the design value of an action E
d
is generally
determined from the design values of the actions, the geometric variables and, if
necessary, the material properties as follows:
to be multiplied by the upper or lower limit for
E
d
¼
E
ð
F
d
;
1
;
F
d
;
2
; ...;
a
d
;
1
;
a
d
;
2
; ...;
X
d
;
1
;
X
d
;
2
; ...Þ
In the case of geometric and physical non-linear calculations according to second-
order theory,
~
a
d
¼
{height, cross-section, inclination
w
a
}and
~
x
d
¼
{f
cR
,f
yR
,f
p0.1R
}
¼~
x
R
describe the deformation characteristics of the loadbearing structure dependent
on the dimensions of the structure, imperfections and material laws. These are taken
into account, for example, with the help of the bending moment-curvature relation-
ships (see Section 3.3).
The following generally applies to onshore wind turbines [9] for group N (normal and
extreme), or to offshore wind turbines [11] for groups N (normal), E (extreme) and T
(transport/erection):
E
d
¼
E
X
(
)
X
i
1
g
Q
;
i
j
1
g
G
;
j
G
k
;
j
;
g
P
P
k
;
Q
k
;
i
; ~
a
d
; ~
x
R
