38

Part  B  -  Verifications  and  approval  requirements

Verifications  in  the  Fatigue  Limit  State  (FLS):
•  During  the  verification  control  process,  the  special  issues  related  to  offshore  structure  fatigue ­
  shall  be  accordingly  taken  account  of  alongside  the  provisions  contained  in  the  respective ­
  rules  of  technology  introduced  by  the  construction  authorities  during  the  fatigue
verification  process.  Suitable  measures  with  respect  to  special  boundary  conditions  such
as  implementation  in  seawater  in  the  North  or  Baltic  seas  (please  compare  this  with  the  corrosion ­
  regulations  for  offshore  areas),  free  corrosion  areas,  or  aspects  connected  with  increased ­
  load  change  figures  (please  compare  this  with  the  DIBt  guideline  for  wind  turbines),
shall  be  included  in  the  draft.
•  For  amendments  with  respect  to  verifications  in  the  fatigue  limit  state,  please  refer  to  Appendix ­
  4  (for  offshore  wind  turbines)  and  Appendix  5  (for  offshore  stations).
Verifications  in  the  Serviceability  Limit  State  -  SLS:
•  Limitation  of  deformation,  possibly  also  accelerations,
•  Limitation  of  concrete  compressive  stresses,  concrete,  resp.  prestressed  steel  stresses  and
decompression  and
•  Limitation  of  concrete  crack  widths.

Verifications  of  durability:
•  Verification  of  the  corrosion  protection  concept:
-  Cathodic  corrosion  protection  with  sacrificial  anodes  in  combination  with  coatings  or  by
impressed-current  systems  and
-  Coatings
-  Allowance  for  rust  in  areas  on  which  high  demands  are  placed.
Verifications  in  the  Accidental  Limit  State  -  ALS:
•  In  as  far  as  such  conditions  exist.
Evaluation  of  hull-retaining  properties  of  the  support  structure:
•  Appropriate  verification  detailing  the  potential  damage  to  a  ship’s  hull  on  collision  between
an  unmanoeuvrable  ship  and  the  support  structure  of  an  offshore  wind  turbine
Special  points  to  be  considered  in  connection  with  the  verification  of  steel  structures:
•  The  stability  verification  for  circular  cylindrical  shells  may  be  obtained  by  proceeding  in  accordance ­
  with  the  DIBt  guideline  “Wind  turbines  -  Actions  on  and  verification  of  stability
against  collapse  for  tower  and  foundation”  (October  2012).
•  Verification  of  the  fatigue  limit  state  for  driven  piles  (also  for  monopiles)  shall  take  account
of  the  proportion  of  damage  resulting  from  the  actual  pile-driving  process.
•  When  designing  the  shear  keys  in  a  grouted  joint  connection,  in  particular,  one  should  not
ignore  the  possible  overlap  of  bending  moments  with  vertical  force.  Both  the  choice  of  materials ­
  and  the  verification  of  the  design  calculations  are  subject  to  an  individual  Technical
Approval  from  the  respective  approval  authority.
•  Static  verification  of  grouted  joint  connections  may  be  obtained  in  accordance  with  the  recommendations ­
  of  GL  or  DNV  using  the  finite  element  method  and,  if  necessary,  confirmed
by  laboratory  tests  conducted  by  an  accredited  test  institute.