1. Additional Features

This group gives a description of special features that normally are not used in analysis of flexible riser system.

1.1. Local element axis definition

Additional to Arbitrary system AR.

This data group may be used to specify a reference vector that is used to determine the initial orientation of the local y- and z-axes of beam elements.

If a local element axis is not specified for an element, the default procedure described in Line, line type and supernode connectivity is used.

This data group must be given for all elements with a CRS6 cross section as the reference vector and the element’s x-axis define the net plane during static and dynamic analysis.

1.1.1. Data group identifier, one input line

LOCAl ELEMent AXIS

1.1.2. Number of input lines for special axis definition, one input line

NAXDEF
  • NAXDEF: integer: Number of input lines for special axis definition

1.1.3. Specification of reference vector for definition of the local axes in the initial configuration, NAXDEF input lines

LINE-ID ISEG IEL RNX RNY RNZ
  • LINE-ID: character(8): Line identifier.

  • ISEG: character/integer: Local segment number within line LINE-ID

    • = ``0’ or `ALL' means all segments in specified line

  • IEL: character/integer: Local element number within segment ISEG

    • = `0’ or `ALL' means all elements in specified segment `ISEG

  • RNX: real: X-component of the reference vector

  • RNY: real: Y-component of the reference vector

  • RNZ: real: Z-component of the reference vector

The reference vector is to be given in global system.

The element’s local x-axis goes from end 1 to end 2 of the element.

The element’s local z-axis is given by the cross product between the element’s local x-axis and the reference vector.

The element’s local y-axis is given by the cross product of the local z-axis and the local x-axis.

The reference vector must not be parallel with the element’s initial x-axis. For CRS6 cable/bar cross sections, the reference vector must be chosen so that it is not parallel to the element’s x-axis during the static and dynamic analyses.

For beam elements, the element axes are found at the stress-free configuration and will subsequently follow the element.

1.2. Fish net cross section

A fish net is subdivided into sections where each section is represented by a cable/bar element with equivalent properties.

Note that the fish net load model requires that the net plane is defined. The net plane is the plane containing the updated local element X-axis and the fixed reference vector specified in the input group LOCAL ELEMENT AXIS.

1.2.1. Data group identifier

NEW COMPonent CRS6

1.2.2. Component type identifier

CMPTYP-ID TEMP
  • CMPTYP-ID: character(8): Component type identifier

  • TEMP: real: Temperature at which the specification applies. In the present version this item serves only as label

1.2.3. Mass and volume

AMS AE
  • AMS: real: Mass/unit length \(\mathrm {[M/L]}\)

  • AE: real: External volume per length \(\mathrm {[L^2]}\)

1.2.4. Stiffness properties classification

IEA
  • IEA: integer: Axial stiffness code

    • 1: constant stiffness

    • N: table with N paris of tension - elongation to be specified 2 ⇐ N ⇐ 10

1.2.5. Axial stiffness. Case 1 IEA = 1

EA
  • EA: real > 0: Axial stiffness \(\mathrm {[F]}\)

1.2.6. Axial stiffness. Case 2 IEA = N

EAF(1) ELONG(1) . . . EAF(N) ELONG(N)
  • EAF(1): real: Axial force corresponding to relative elongation ELONG(1) \(\mathrm {[F]}\)

  • .

  • .

  • .

  • ELONG(N): real: Relative elongation \(\mathrm {[1]}\)

EAF and ELONG must be given in increasing order.

1.2.7. Net properties

SN WIDTH1 WIDTH2 REDVEL
  • SN: real: Solidity ratio \(\mathrm {[1]}\)

  • WIDTH1: real: Net width at segment end 1 \(\mathrm {[L]}\)

  • WIDTH2: real: Net width at segment end 2 \(\mathrm {[L]}\)

  • REDVEL: real: Reduction factor for current velocity

1.2.8. Damping specification

Identical to input for cross-section type CRS1, see data group Damping specification.

1.2.9. Hydrodynamic force coefficients

AMX AMY
  • AMX: real: Added mass per length, tangential direction \(\mathrm {[M/L]}\)

  • AMY: real: Added mass per length, normal direction \(\mathrm {[M/L]}\)

1.2.10. Capacity parameter

TB YCURMX
  • TB: real: Tension capacity \(\mathrm {[F]}\)

  • YCURMX: real: Maximum curvature \(\mathrm {[I/L]}\)

These parameters are dummy in the present version.