Construction of prestressed concrete towers - Concrete Structures for Wind Turbines - page 193

5.3 Prestressed concrete towers with precast concrete segments

5.3.1 Examples of design and construction
Towers in reinforced or prestressed concrete are mostly described as in situ concrete
structures in tenders. Support structures with post-tensioned precast concrete
segments are frequently offered as alternatives for towers up to heights of approx.
100m.
In order speed up operations on site, the Enercon company has developed a design
using precast concrete rings for towers with a hub height of 98 m (E-70 turbine); for
details see [8]. Specially fabricated separate internal and external steel moulds are kept
in stock for each of the 23 elements of the tapering concrete tower for an E-70 turbine
(Figure 5.2). The reinforcement is installed using a winding technique which employs
templates fitted to special rotary machines. The precast concrete elements are delivered
to the site by road on low-loaders. Owing to their size, the bottommost segments are
cast as pairs of half-shells (Figure 5.3).
After arrival on site, these half-shells are assembled with a 300 t telescopic crane.
The completed annular segments are then erected with a 600 t crawler-mounted
crane. The precast concrete elements are joined together with an epoxy resin

Fig. 5.2 Moulds for tower segments

Fig. 5.4 Enercon E-126 wind turbine

Fig. 5.3 Half-shell