Loadbearing structures and detailed design - Concrete Structures for Wind Turbines - page 145

X X

d þ X
i ð reveal Þ

A si ¼ ! N Ed

ð s ci þ s si þ r s Þ A ci s ci B i s si

i ð shell Þ i ð opening Þ

X
i ð shell Þ s ci þ s si þ r s

X
i ð opening Þ s ci

ð Þ A ci r i cos a i B i d r i cos a i

þ X
i ð reveal Þ

a i ¼ ! M z ; Ed

s si A si r i cos

X X

ð s ci þ s si þ r s Þ A ci r i sin a i s ci B i d r i sin a i

i ð shell Þ i ð opening Þ

þ X a i ¼ ! 0

i ð reveal Þ s si

A si r i sin

The ultimate limit state can therefore be verified:
e c2 e i e su
A temperature gradient in the shaft wall (see Section 2.7) does not need to be
considered during the design either because
e c2 þ e T ¼ 2

: 0

% þ 0

: 075

% ¼ 2

: 075

% < e c2u ¼ 3

: 5

%
Details can be found in [8], which uses a telecommunications tower as an example.

4.7.4 Special characteristics of prefabricated construction

4.7.4.1 Terminology
Prestressed concrete members made up of smaller precast concrete elements are
characterised by the fact that the individual elements are assembled in the loadbearing
direction and then post-tensioned together.
The joints between the elements are in the form of compression or filled joints, using
materials with a cement or polymer binder. Reinforcing steel crossing the joints is not
provided. Grouted post-tensioned tendons are installed in the loadbearing direction.
Reinforcing steel is provided in the individual precast concrete elements and they can
be prestressed, for example, transverse to the principal loadbearing direction.
Compression joint:
A fine mortar based on cement or a polymer resin (adhesive) which is compressed by
post-tensioning the elements together immediately after being applied to the faces of
the joint; any excess mortar exudes out of the joint.
Filled joint:
The elements are not post-tensioned together until after the compacted mortar or
concrete of the joint has reached a sufficient degree of hardness.
Shear force transfer across fully overcompressed joints:
Eq. (84) from DIN 1045-1 [33] 10.3.6 should be applied here in a suitable form. As the
end faces of the elements are generally cast without any profile, c j ¼ 0 may be used