Appendices 
91 
While simulating the collision scenarios, the following criteria shall be observed: 
Requirements concerning the offshore wind turbine model 
• The model of the structure in its totality must be sufficiently detailed. Mass, inertial load and 
stiffness shall be considered. 
• The bedding conditions shall be applied to the foundation elements by means of elastic 
springs (e. g. p-y model). Clamping at the top edge of the uppermost ground layer is not 
permitted. 
• The material models and the failure criteria shall be selected and documented in a suitable 
manner. 
• Details, such as boat landings, may be neglected if it can be guaranteed that these do not 
represent a supplementary danger to the integrity of the hull. 
Requirements pertaining to the model of the ship 
• The properties of the standard ship (geometry of the midship section, space of frame, thick 
ness of the shell, position of the heavy fuel oil tank) shall be selected in consideration of the 
actual situation of the individual reference ship and shall be documented in detail. 
• In addition to the mass and inertial loads of the ship, the hydrodynamic mass (approx. 20% 
of the mass of the ship) shall be considered. 
• The boundary conditions for the movement of the ship shall be reasonably selected. For 
example, the force resulting from a change of draught or righting moment in the case of 
heeling shall be suitably integrated into the model. Rotation around the vertical axis shall 
only be permitted to a minor extent, or shall be excluded entirely, as such rotation results in 
minor damage to the ship and the offshore structure. This shall be achieved by appropria 
tely selecting the boundary and/or the initial conditions. 
• The calculation of the drifting velocity is based on the assumptions of the BMVI working 
group “Approval-relevant Recommended Guidelines” and shall assume a ship drifting side 
ways at 2 m/s. All other ship movements and the derivable consequences of these move 
ments with respect to drifting towards an offshore structure (e.g. due to accelerations, dis 
placements, and rotations) may be reduced to zero, if they cannot be represented 
realistically. Furthermore, single peak loads resulting from environmental conditions, such 
as wind, currents and swell, may be neglected, insofar as they are not representable in a 
realistic manner within the scope of the calculations. The respective assumptions included 
in the expert opinion are to be accordingly explained and justified. The ship does not have 
its own propulsion. Loads resulting from environmental conditions, such as wind and cur 
rent, may also be neglected, insofar as these are not representable in a realistic manner. 
• The material models and the failure criteria shall be suitably selected and documented, in 
particular for higher-tensile steel. 
Quality criteria for the collision analysis 
• Different scenarios are to be simulated, whereby the parameters (water level, angle of im 
pact etc.) shall be selected conservatively. 
• If simulations are used, the contact between the ship and the offshore wind turbine, as well 
as the contact between the individual components, shall be simulated in a suitable man 
ner. 
• The size of the elements shall be selected in such way that deformations (dents, bucklings, 
etc.) can be represented realistically. 
• In particular, the element formulation (number of integration points, fully integrated or redu 
ced integrated elements, no tetrahedron/triangle elements...) shall be carefully selected for 
the simulations. Particular attention is to be paid to the quality criteria inherent to the pro 
gramme used for the elements (taper, skew etc.)