1. CRS0 - Thin-walled pipe cross section

This cross-section allows for simplified input of circular, homogenous cross-sections. The input format is convenient for metallic pipe cross sections.

A thin-walled pipe cross section example is shown below. Subsequent sections give details and further options.

'**********************************************************************
        NEW COMPONENT CRS0
'**********************************************************************
'                            units: Mg kN m C
'       icmpty  temp
        pipe500 20.
'
'       diast   thst   densst  thex     densex
        0.5     0.015  7.85    0.15      0.4
'       metkind emod       gmod
        1       206000E3   79000E3
'
'       dh is the hydrodynamic diameter
'       icode=2 => dimensionless hydrodynamic force coefficients
'       cqx      cqy      cax     cay     clx   cly    icode   dh
        0.0      0.8      0.      0.60    0.    0.     2       0.9
'
'       tb       ycurmx
        1.       0.4329

1.1. Data group identifier

NEW COMPonent CRS0

1.2. Component type identifier

CMPTYP-ID TEMP ALPHA BETA

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

  • TEMP: real, default: 0: Temperature at which the specification applies \(\mathrm {[Temp]}\)

  • ALPHA: character/real, default: 0: Thermal expansion coefficient \(\mathrm {[Temp^{-1}]}\)

    • = STEE: The value \(\mathrm {1.2\times 10^{-5}}\) is used

    • = TI23: The value \(\mathrm {9.0\times 10^{-6}}\) is used

    • These values are applicable for temperatures in Celcius or Kelvin

  • BETA: character/real, default: 0: Pressure expansion coefficient \(\mathrm {[1/(F/L^2)]}\)

    • BETA gives the expansion of an element with zero effective tension from the difference between the internal and the external pressure.

    • = PIPE: thin walled pipe assumption. BETA is calculated from the parameters given in Thin-walled pipe cross section_cross (below) as: \(\mathrm {\frac{DIAST(1-2\nu)}{4THST\times EMOD}}\) where \(\mathrm {\nu=\frac{EMOD}{2GMOD}}-1\)

Axis symmetric pipe cross section

image::um_ii_fig56.svg [title="Axis symmetric pipe cross section",width=456]

1.3. Cross-section parameters

DIAST THST DENSST THEX DENSEX R_EXTCNT R_INTCNT

  • DIAST: real: Diameter of pipe \(\mathrm {[L]}\)

    • DIAST > 0: Outer diameter of pipe

    • DIAST < 0: Inner diameter of pipe

  • THST: real: Thickness of pipe \(\mathrm {[L]}\)

  • DENSST: real: Density of pipe material \(\mathrm {[M/L^3]}\)

  • THEX: real, default: 0: Thickness of external coating \(\mathrm {[L]}\)

  • DENSEX: real, default: 0: Density of external coating \(\mathrm {[M/L^3]}\)

  • R_EXTCNT: real, default: 0: Outer contact radius \(\mathrm {[L]}\)

  • R_INTCNT: real, default: 0: Inner contact radius \(\mathrm {[L]}\)

Buoyancy is calculated from the total external diameter \(\mathrm {DIAST+2\times THEX}\) (For DIAST > 0) or \(\mathrm {|DIAST|+2\times THST+2\times THEX}\) (For DIAST < 0).

The outer and inner contact radii of the cross section, R_EXTCNT and R_INTCNT, are used for * seafloor contact * pipe-in-pipe contact * Tubular contact point specification

The default values of R_EXTCNT and R_INTCNT are zero in the present version.

1.4. Material properties

Material constants
MATKIND EMOD GMOD SIGY EMODY/NPAIR HARPAR NCIRC

  • MATKIND: integer: Type of material model

    • MATKIND = 1: linear material

    • MATKIND = 2: elastic-plastic

    • MATKIND = 3: strain-stress curve

    • MATKIND = 4: linear material including shear deformation

  • EMOD: real > 0: Modulus of elasticity \(\mathrm {[F/L^2]}\)

  • GMOD: real > 0: Shear modulus \(\mathrm {[F/L^2]}\)

  • SIGY: real: Yield stress \(\mathrm {[F/L^2]}\)

  • EMODY/NPAIR: real/integer:

    • MATKIND = 2: Slope of strain-stress curve for plastic region \(\mathrm {[F/L^2]}\).

      • EMODY < EMOD

    • MATKIND = 3: Number of user specified strain-stress relations

      • 2 ⇐ NPAIR ⇐ 99

  • HARPAR: real, default: 1: Hardening parameter for material

    • 0 ⇐ HARPAR ⇐ 1

    • HARPAR = 1: Kinematic hardening

    • HARPAR = 0: Isotropic hardening

  • NCIRC: integer >= 8, default: 16: Number of integration points along circumference

For MATKIND = 1 or 4: Only EMOD and GMOD are used

For MATKIND = 4: The shear stiffness is calculated as: \(\mathrm {GMOD\frac{\pi (D_e^2-D_i^2)}{4}0.5}\)

For MATKIND = 3: NPAIR input lines of the strain-stress curve must be given Section 1_strain.

Strain-stress curve (NPAIR input lines to be specified for MATKIND=3)
EPS(I) SIG(I)

  • EPS(i): real: Strain for point i on strain-stress curve \(\mathrm {[1]}\)

  • SIG(i): real: Stress for point i on strain-stress curve \(\mathrm {[F/L^2]}\)

The first point in the stress-strain curve is automatically deduced: EPS(0) = SIGY/EMOD, SIG(0) = SIGY. This point is taken as the proportionality limit of the material, at which the yield/hardening process starts. EPS(i) and SIG(i) are to be given in increasing order. The gradient of the curve must decrease with increasing strain.

1.5. Bending-torsion geometric coupling specification for MATKIND = 1 or 4

This data group is optional, and can only be applied for MATKIND = 1 or 4.

BTGC

  • BTGC: character(4): bending-torsion coupling identifier.

If the BTGC identifier is present, geometric coupling between torsion and bending is accounted for.

1.6. Damping specification

Identical to input for cross-section type CRS1 except that the local axial friction model, AXFRC, is illegal for CRS0, see Damping specification.

1.7. Hydrodynamic load types

Identical to input for cross-section type CRS1 except that the load type HNET is not available, see Hydrodynamic load type.

1.8. Aerodynamic force coefficients

Identical to input for cross-section type CRS1, see Aerodynamic load type identification.

1.9. Capacity parameter

Identical to input for cross-section type CRS1, see Capacity parameter.