Environmental Engineering Reference
In-Depth Information
4.10.6 Design of circular ring beam
The circular ring beam is designed for the resultant tensile forces in the layers of
reinforcement at the ultimate limit state. The statically indeterminate forces shown in
Figure 4.50 are determined in a similar way to the internal forces in the circular ring
beam, that is from the design values of the internal forces at the ultimate limit state.
Fig. 4.50 Circular ring beam detail for an abrupt change in tower diameter
internal forces
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4.11
Foundation design
4.11.1 Calculating the internal forces
A number of special aspects are relevant when calculating the internal forces
according to second-order theory in relation to the interaction between tower,
foundation and subsoil [78]. Our starting point is the safety concept described in
DIN 1055-100 [44]. This is characterised by safety elements (partial safety and
combination factors) based on semi-probabilistic methods, also by the fact that we
distinguish between the serviceability and ultimate limit states.
Accordingly, we distinguish between three ultimate limit states:
a) Loss of equilibrium of a structure, for example due to uplift, overturning or
buoyancy.
b) Failure of the loadbearing structure, one of its parts or the foundation, for example
due to rupture, excessive deformation, conversion into a kinematic chain, loss of
stability or sliding.
c) Failure of the subsoil, for example due to slope or ground failure; verification of this
limit state is to be carried out as an analysis of the overall stability to DIN 1054 [50]!
This distinction results in unambiguous and compatible interfaces between the
structural and geotechnical engineering responsibilities. Limit state type (b) governs
in all cases in which structure and subsoil act together. The compatibility between the
design situations to DIN 1055-100 [44] and the traditional load cases 1 to 3 of
geotechnical engineering are illustrated in [44] Table A.3.
