Part  B  -  Verifications  and  approval  requirements

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Notes:
•  With  regard  to  certifying  the  fatigue  strength  of  reinforced  concrete  and  prestressed  concrete ­
  components,  reference  is  herewith  made  to  DASt  publication  439  (Berlin  1994)  “Fatigue ­
  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  Analysis ­
  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  calculations ­
  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  construction ­
  conditions,  i.e.  temporary  conditions  and  conditions  of  limited  duration  during  the  erection ­
  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  documentation. ­
  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  operation. ­

Verification  in  the  Ultimate  Limit  State  -  ULS:
•  Strength  verification
•  Stability  verification  and
•  Verifications  pertaining  to  force  application  and  connections.