Environmental Engineering Reference
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Figure 12: Calculated extreme moments for the 10-turbine analysis group.
Figure 12 shows the primary extreme moment results for the 10-turbine analysis
group. The tower overturning moment is the largest value due to the thrust force
acting over the long lever arm of the tower height.
The main shaft torque dominates the loads carried by the MH structure. While
many of the load cases impart signifi cant forces and moments to this structure, the
main shaft torque drives the overall level. A 3-MW WT must resist about 7330 kNm
of moment about the shaft in the MH. This is equivalent to about 12 tank-meters.
These loads increase nearly fi vefold for a turbine rated at the 10 MW level, or
about 55 tank-meters. One quickly appreciates the level of loads that this repre-
sents by imagining 55 M1A2 Abrams tanks at the end of a 1-m moment arm trying
to twist-off the top of the turbine.
The amount of thrust absorbed by the rotor and turbine support structure is
shown in Fig. 13. A 3 MW rated WT will have about 816 kN of axial force applied
at the main shaft location, or the equivalent weight force of about 1.3 M1A2
Abrams tanks.
The previous examples are for extreme loads, but more important to consider
are the time-varying or fatigue loads, which mechanically work the structure,
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