Part B - Verifications and approval requirements 
37 
Notes: 
• With regard to certifying the fatigue strength of reinforced concrete and prestressed con 
crete components, reference is herewith made to DASt publication 439 (Berlin 1994) “Fa 
tigue Strength of Reinforced Concrete and Prestressed Concrete Components” and the 
explanations pertaining to verification in line with CEB-FIP Model Code 1990. 
• With regard to the structural design of solid structures, reference is herewith made to the 
current version of the DNV-OS-C502 “Offshore concrete structures” guidelines. 
• With regard to verifications using the finite element method, reference is herewith made to 
the GL Guideline for the Certification of Offshore Wind Turbines chapter 5.A “Strength Ana 
lysis with the Finite Element Method”. 
2.3.2 Requirements and required verifications 
The final design shall be verified by the appointed inspector through independent parallel cal 
culations with respect to the structural integrity of the offshore structure. The results of this 
verification shall be represented in the verification report in a manner that is comprehensible 
and transparent. 
The support structure shall be verified under due consideration of all the respective construc 
tion conditions, i.e. temporary conditions and conditions of limited duration during the erec 
tion and transport phases (incl. wave loads). Both the storage conditions and the material 
characteristics resulting from long and short-term loads shall be given due consideration for 
all the different static/dynamic systems concerned. 
If such a construction state should last longer than six months, the respective rusting rate for 
the installation period shall be accordingly taken into account in the verification documenta 
tion. Alternatively, a temporary corrosion protection system may be implemented during the 
construction phase. 
Taking the dynamic effects of the wind turbine into consideration: 
• The influence line for calculating the support structure, incl. the foundation elements, shall 
be determined by calculating the overall dynamics. 
Proof shall be provided to confirm that the excitation frequencies of the installation and the 
natural frequencies of the support structure are suitably far apart. This shall be confirmed 
by calculations conducted using the following two equations: 
” f R / f 0 ,i - 0-95 
where f R = max. rotation frequency of the rotor during normal operation and 
where f 01 = first natural frequency of the support structure and 
" f R .m / f o,n ~ 0-90 resp. ^ 1 .05 
where f Rm = blade passing frequency of the m rotor blades and f 0n = n th natural 
frequency of the support structure. 
If it is planned to operate within the danger zone, vibration monitoring is required during op 
eration. 
Verification in the Ultimate Limit State - ULS: 
• Strength verification 
• Stability verification and 
• Verifications pertaining to force application and connections.