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*Block

Purpose

To input the fatigue analysis wave scatter diagram, including the definition of blocks and/or reference seastates as appropriate.

Theory

Refer to Long Term Environmental Conditions for further information on this feature.

Keyword Format

The way in which this keyword is included in the seastate file depends on how you want to specify the seastate information, as follows:

For one seastate, the format of the keyword in the file is as follows, with line 3 repeated for as many seastate values as you want to specify:

*BLOCK

REFERENCE=Hs, Tz/Tp, Number of Occurrences, DIRECTION=Direction, FILE=File Name

Hs, Tz/Tp, Number of Occurrences

For selected seastates, the REFERENCE= line is repeated for each seastate block that you want to define, with line 3 repeated for as many seastate values as you want to include within that seastate block:

*BLOCK

REFERENCE=Hs, Tz/Tp, Number of Occurrences, DIRECTION=Direction, FILE=File Name

Hs, Tz/Tp, Number of Occurrences 

For all seastates, the REFERENCE= line is repeated for every seastate value:

*BLOCK

REFERENCE=Hs, Tz/Tp, Number of Occurrences, DIRECTION=Direction, FILE=File Name 

This keyword is required for the Postprocessor with RAOs mode, but is not relevant to Postprocessor with Stress Spectra mode. Direction can be N, NW, W, SW, S, SE, E or NE.

seastate scatter diagram

Purpose

To input the fatigue analysis wave scatter diagram, including the definition of blocks and/or reference seastates as appropriate.

Table Input

Notes

(a)The scatter diagram is defined in terms of significant wave height (Hs) and mean zero up-crossing period (Tz), or wave spectrum peak period (Tp). If there is no occurrence of a particular combination of Hs and Tz/Tp, you simply leave the corresponding cell blank.

(b)The duration of the period measuring the number of occurrences is in fact immaterial - LifeFrequency transforms the data you specify into percentage occurrence values, so it is the relative magnitudes only of the entries that are of importance.

(c)The Mark Seastate Blocks option is used to group seastates into blocks. This task can be performed at any stage during the input of the scatter diagram data, but would typically be performed after all of the Hs/Tz or Hs/Tp data has been input. You may also delete blocks subsequently, allowing you to change the way in which seastates are grouped in blocks without inputting the scatter diagram again in full.

(d)The Mark Reference Seastates option is used to nominate reference seastates within each block. This task can only be performed after one or more seastate blocks have been defined. If you click on a seastate in a block where a reference seastate is already nominated, the previous nomination becomes deselected.

Pre-run analyses

Purpose

To specify a list of Pre-Run Analyses, consisting of the Flexcom analyses corresponding to the scatter diagram reference seastates.

Table Input

Notes

(a)You must specify an RAO file name in the Pre-Run Analyses table for each reference seastate for each direction with non-zero percentage occurrence.

(b)You do not need to specify a file type in the Flexcom Analysis input, just the analysis root or generic name.