1. Time domain T-N fatigue damage

This option allows for calculation of fatigue damage calculation from rension in beam or bar elements using a specified T-N curve and rainflow cycle counting.

The calculated fatigue damage is per year of the specified environmental conditions.

The fatigue damage is calculated based on the stored force time series from DYNMOD (see data group File storage for internal forces for storage information).

1.1. Data group identifier, one input line

TN FATIgue DAMAge       NoPlot

1.2. Control data, one input line

CHSOLVE NSECT TBEG TEND FAT-ID
  • CHSOLVE: character(6), default: RIFLEX: Source for force time series. Currently only RIFLEX is allowed.

  • NSECT: integer >= 0, default: 0: Number of specifications for fatigue analysis

    • NSECT = 0: All elements where forces are available are included in the analysis

  • TBEG: real >= 0, default: 0: Beginning of interval for fatigue calculation \(\mathrm {[T]}\).

    • The default is the first time step in the stored force time series.

    • Must be less than the simulation length.

  • TEND: real >= 0, default: 0: End of interval for fatigue calculation \(\mathrm {[T]}\).

    • The default is the last time step in the stored force time series.

    • If the specified value is larger than the length of the stored force time series, it will be set to the the last time step in the stored force time series.

  • FAT-ID: character(16): Identifier for fatigue calculation. Used in result presentation only

The remaining of the time series is used if TEND is zero (Default is full time series).

1.3. Fatigue calculation options, one input line

IOPCAL
  • IOPCAL, integer, default: 0: Fatigue calculation option

    • IOPCAL = 0: Effective tension is used

1.4. T-N curve data, two input lines

T-N fatigue capacity curve description

NOSL RBS
  • NOSL: integer = 1, default: 1: Number of straight lines defining the SN curve. Must be 1 in present version.

  • RBS: reak > 0. Reference breaking strength \(\mathrm {[F}\)

Fatigue capacity curve constants

M K
  • M: real > 0: Slope of the T-N curve

  • K: real > 0: Constant defining the T-N curve

um io fig325
Figure 1. Example 1: 2 segments and fatigue limit. Note that FATLIM can be alternatively specified

For a single slope T-N curve, log cycles as a function of log tension range:

\(\mathrm {N=C\times \Delta S^{RM1}}\)

or

\(\mathrm {logN=RC1-|RM1|\times log\Delta S}\)

Where:

  • \(\mathrm {N}\): Number of cycles to failure

  • \(\mathrm {\Delta S}\): Stress range

  • \(\mathrm {C=10^{RC1}}\)

or log stress as a function of log cycles:

\(\mathrm {log\Delta S=\frac{RC1}{|RM1|}-\frac{logN}{|RM1|}}\)

1.5. Element specification, NSECT input lines

LINE-ID ISEG IEL IEND
  • LINE-ID: character(8): Line identifier

  • ISEG: integer >= 0, default: 0: Segment number on line

    • = 0: All segments in specified line

  • `IEL: integer >= `0, default: 0: Local element number in specified segment

    • = 0: All elements in specified segment

  • IEND: integer, default: 0: Element end(s). Allowed values are:

    • IEND = 0: Fatigie calculated at both element ends

    • IEND = 1: Fatigie calculated at end with smallest node number?

    • IEND = 2: Fatigie calculated at end with largest node number?

Time domain forces for the specified elements must be stored in DYNMOD, see data group File storage for internal forces for storage information.

If several specifications match an element, the first specification will be used.