1. CRS5  Partly submerged general shaped cross section
This cross section is used for floating structural members. It can only be used for elements with local zaxis approximately parallel the global zaxis pointing in the same direction. The roll and pitch angles are restricted to 30\(\mathrm {^{\circ}}\) as a practical upper limit. The stiffness properties are based on two symmetry planes, while area and hydrodynamic force coefficients are calculated based on the cross section description represented by offset points symmetric with regard to the vertical (z) axis. For hydrodynamic load computation the element is divided into subelements specified in data section Segment specification. NSEG input lines. The cross section can only be used when consistent formulation is applied (see STAMOD: External, static loads) and for nonlinear dynamic analysis with regular waves.
1.2. Component type identifier
Identical to Component type identifier for CRS2.
1.3. Mass and volume
Identical to Mass and volume.
1.4. Stiffness properties classification
Identical to Stiffness properties classification for CRS2
1.5. Axial stiffness. Case 1, IEA=1
Identical to Axial stiffness. Case 1
1.6. Axial stiffness. Case 2, IEA=N
Identical to Axial stiffness. Case 2
1.7. Bending stiffness. Case 1, IEJ=1 IPRESS=0
Identical to Bending stiffness. Case 1
1.8. Bending stiffness. Case 2, IEJ=1 IPRESS=1 (not implemented)
Identical to Bending stiffness. Case 2
1.10. Bending stiffness. Case 4 IEJ=N1, IPRESS=N2 (not implemented)
Identical to Bending stiffness. Case 4 IEJ=N1
1.11. Damping specification
Identical to Damping specification for CRS2
1.12. Hydrodynamic force coefficients
CDX CDY CDZ CDTMOM AMX

CDX: real
: Drag force coefficient per length, tangential \(\mathrm {[F/((L/T)^2\times L)]}\) 
CDY: real
: Drag force coefficient per length, local yaxis \(\mathrm {[F/((L/T)^2\times L)]}\) 
CDZ: real
: Drag force coefficient per length, local zaxis \(\mathrm {[F/((L/T)^2\times L)]}\) 
CDTMOM: real
: Drag coefficient around local xaxis
Dummy in present version.


AMX: real
: Added mass per length, tangential \(\mathrm {[M/L]}\)
All hydrodynamic force coefficients applies to fully submerged cross section. That is, the actual coefficients are proportional to submerged volume. The drag force coefficients are to be scaled according to consistent units used, see Unit names and gravitational constant.
The tangential drag force which is a friction force acting along the local xdirection is calculated according to:

\(\mathrm {F_t=CDX\times (A_{sub}/A_{tot})\times V_{x,rel}\times V_{x,rel}}\)
The viscous normal force per unit length is calculated using the drag force term in Morisonâ€™s equation and assuming the drag force direction is parallel the instantaneous relative velocity transverse component:

\(\mathrm {F_y=CDY\times (A_{sub}/A_{tot})\times \sqrt{V^2_{y,rel}\times V^2_{z,rel}}\times V_{y,rel}}\)

\(\mathrm {F_z=CDZ\times (A_{sub}/A_{tot})\times \sqrt{V^2_{y,rel}\times V^2_{z,rel}}\times V_{z,rel}}\)
where: * \(\mathrm {A_{sub}}\): is instantaneous cross section submergence * \(\mathrm {A_{tot}}\): is total external areal of the cross section * \(\mathrm {V_{x,rel}}\): is relative water velocity in local xdirection * \(\mathrm {V_{y,rel}}\): is relative water velocity in local ydirection * \(\mathrm {V_{z,rel}}\): is relative water velocity in local zdirection
1.13. Description of cross section shape
NOB NSUB NROLL NDFS

NOB: integer
: Number of offset points to describe the cross section shape.
Only one half of the shape is described due to assumed symmetry about local zaxis.

3 <= NOB <= 20


NSUB: integer, default: 20
: Number of points of submergence in table of submerged volume as function of submergence and roll angle. 
NROLL: integer, default: 20
: Number of roll angles in table of submerged volume as function of submergence and roll angle. 
NDFS: integer, default: 20
: Number of points of submergence in table of added mass and poten tial damping as function of submergence.
The submerged cross section area is calculated for a number of
submergence positions and relative roll angles in the range (0

\(\mathrm {\pi }\)/2
). The instantaneous submerged area is
found by linear interpola tion for points lying between those given in
the table.
Tables of twodimensional added mass and potential damping as function of submergence are calculated using the Frank.closefit technique. The instantaneous added mass and damping are found by linear interpolation for points lying between those given in the tables.
1.14. Offset points
INB YB ZB

INB: integer
: Offset point number 
YB: real
: Local ycoordinate for offset pointINB

ZB: real
: Local zcoordinate for offset pointINB
Only one half of the cross section shape is modelled due to the assumed symmetry about local zaxis.
The offset points must be given in increasing order with decreasing
value of the zcoordinate. YB
and ZB
are referred to the principal
local axis. YB >= 0
and first and last value of YB
has to be zero,
see the figure below.
1.15. Capacity parameter
Identical to Capacity parameter for CRS2