1. Stress envelope curves

This option allows for calculation of stress envelopes from the element forces stored in DYNMOD, see data group File storage for internal forces for storage information.

1.1. Data group identifier

STREss ENVElope CURVes      Noplot

1.2. Print options, one input line

LINE-ID IDOF1 IDOF2 IDOF3

  • LINE-ID: character(8): Line identifier

    • ILINE = ALL: Stresses in all lines calculated

  • IDOF1:integer: Stress component type 1

    • IDOF1 = 1: Axial stress

    • IDOF1 = 2: Torsional stress

    • IDOF1 = 3: Bending stress

    • IDOF1 = 4: Axial + bending stress

    • IDOF1 = 5: Shear stress

    • IDOF1 = 6: Shear + torsional stress

    • IDOF1 = 7: Equivalent stress

    • IDOF1 = 8: Hoop stress

    • IDOF1 = 9: Radial stress

  • IDOF2:integer: Stress component type 2

    • See IDOF1

    • Dummy at present

  • IDOF3:integer: Stress component type 3

    • See IDOF1

    • Dummy at present

1.3. Stress calculations options, one input line

TSTA TEND IOP DUR

  • TSTA: real, default: 0: Start time in stress time series \(\mathrm {[T]}\)

  • TEND: real, default: 0: End time in stress time series \(\mathrm {[T]}\)

    • TEND = 0.0: Until last time step used

  • IOP: integer, default: 0: Code for envelope type

    • IOP = 1: Min and max values presented

    • IOP = 2: Maximum range

    • IOP = 3: Standard deviations

    • IOP = 4: Estimated extreme values (not yet implemented)

  • DUR: real, default: 10800: Duration used in extreme value estimation \(\mathrm {[T]}\)

    • Dummy parameter in present version

1.4. Stress calculation location, one input line

NPCS IOPPR THETA INEX IOPPRE

  • NPCS: integer, default: See below: Number of points around the cross-section

    • = 0: max stresses estimated

  • IOPPR: integer, default: 0: Print option

    • IOPPR = 0: Print maximum stresses only

    • IOPPR > 0: Print stresses at all NPRCS points

  • THETA: real, default: 0: Angle for stress calculation \(\mathrm {[Deg]}\)

    • Dummy for NPCS>1

  • INEX: integer, default: 2: Stress loction switch

    • INEX = 1: Inner wall

    • INEX = 2: Outer wall

  • IOPPRE: integer, default: 1: Code for updating inner and outer pressure values.

    • |IOPPRE| = 1: Static inner and outer pressure used.

    • |IOPPRE| = 2: Updated inner and outer pressure used.

    • Outer pressure calculated as hydrostatic pressure from MWL.

    • IOPPRE < 0: Wall forces calculated using outer area given by the pipe diameter or the alternative cross section diameter.

      • Corresponds to evenly distributed shear forces between buoyancy material and pipe.

      • Warning: This option is under development!

Nonlinear time domain analysis only.

The default value for NPCS is dependent on the value specified above for IOP: Default is 0 for IOP = 1, otherwise it is 4.

In the present version, the external pressure is calculated as a hydrostatic pressure from the MWL. The external pressure is updated for all structural elements.

The internal pressure is updated for all elements that are part of a Main Riser Line.

1.5. Stress calculation parameters, one input line

IOPSTR ASTI WSTI DIASTI THSTI EMOD

  • IOPSTR: integer, default: 0: Option for stress calculation

    • IOPSTR=0: Stresses calculated from bending moment (recommended)

    • IOPSTR=1: Stresses calculated from curvatures

  • ASTI: real, default: 0: Alternative cross sectional area \(\mathrm {[L^2]}\)

  • WSTI: real, default: 0: Alternative cross section modulus \(\mathrm {[L^3]}\)

  • DIASTI: real, default: 0: Alternative cross section diameter \(\mathrm {[L]}\)

  • THSTI: real, default: 0: Alternative cross section wall thickness \(\mathrm {[L]}\)

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

    • Bending stresses are calculated from curvature, diameter and EMOD if IOPSTR=1 and EMOD>0

    • \(\mathrm {WST=\frac{2}{EMOD\times DIAST}}\)

The default values of 0 for ASTI, WSTI, DIASTI, THSTI and EMOD are interpreted as no change from the cross-sectional properties given in INPMOD.