The Formwork Experts
6
999771002 - 08/2008 Ü
Introduction
User information Doka forming wagon T
Eurocodes at Doka
In Europe, a uniform series of Standards known as
Eurocodes (EC) was developed for the construction
field by the end of 2007. These are intended to pro-
vide a uniform basis, valid throughout Europe, for
product specifications, tenders and mathematical
verification.
The EC are the world's most highly developed
Standards in the construction field.
In the Doka Group, the EC are to be used as stand-
ard from the end of 2008. They will thus supersede
the DIN norms as the "Doka standard" for product
design.
The widely used "Permissible stress design" (com-
paring the actual stresses with the permissible
stresses) has been superseded by a new safety con-
cept in the EC.
The EC contrast the actions (loads) with the resist-
ance (capacity). The previous safety factor in the
permissible stresses is now divided into several
partial factors. The safety level remains the same!
Comparison of the safety concepts (example)
E
d
Design value of effect of actions
(E ... effect; d ... design)
Internal forces from action F
d
(V
Ed
, N
Ed
, M
Ed
)
R
d
Design value of the resistance
(R ... resistance; d ... design)
Design capacity of cross-section
(V
Rd
, N
Rd
, M
Rd
)
F
d
Design value of an action
Steel:
R
d
=
R
k
Timber: R
d
= k
mod
·
R
k
F
d
=
γ
F
· F
k
γ
M
γ
M
(F ... force)
F
k
Characteristic value of an action
"actual load", service load
(k ... characteristic)
e.g. dead weight, live load, concrete pres-
sure, wind
R
k
Characteristic value of the resistance
e.g. moment resistance to yield stress
γ
F
Partial factor for actions
(in terms of load; F ... force)
e.g. for dead weight, live load, concrete pres-
sure, wind
Values from EN 12812
γ
M
Partial factor for a material property
(in terms of material; M...material)
e.g. for steel or timber
Values from EN 12812
k
mod
Modification factor (only for timber – to take
account of the moisture and the duration of
load action)
e.g. for Doka beam H20
Values as given in EN 1995-1-1 and EN 13377
E
d
R
d
Permissible stress design
EC/DIN concept
F
actual
≤
F
permissible
E
d
≤
R
d
A Load factor
60 [kN]
60<70 [kN]
115.5 [kN]
n
~ 1.65
F
yield
F
permissible
F
actual
98013-100
A
90 [kN]
115.5 [kN]
90<105 [kN]
R
k
R
d
E
d
g
M
= 1.1
g
F
= 1.5
98013-102
A
The "permissible values" communicated in
Doka documents (e.g.: Q
permissible
= 70 kN) do
not correspond to the design values (e.g.:
V
Rd
= 105 kN)!
➤
Avoid any confusion between the two!
➤
Our documents will continue to state the
permissible values.
Allowance has been made for the following
partial factors:
γ
F
= 1.5
γ
M, timber
= 1.3
γ
M, steel
= 1.1
k
mod
= 0.9
In this way, all the design values needed in
an EC design calculation can be ascertained
from the permissible values.
