Timetrace Files |
 
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Timetrace Files |
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The timetrace file stores the values of selected variables at all or selected solution times, and may be in ASCII or binary format. You select the variables to be output to the timetrace file before the solution begins. Normally a relatively small number of outputs is requested, and so the file produced is significantly smaller than a standard (non-customised) database file. This is the one advantage of using the timetrace file option. However, it should be noted that modern versions of Flexcom also support customised database files for storage efficiency, so the case for using timetrace files has greatly reduced.
One disadvantage is that you must know in advance what variables are of interest, and also that your analysis is going to be completed successfully. If you perform a simulation with only timetrace output, and discover subsequently that you omitted some variables of interest, you have no remedy except to repeat the run with the timetrace requests expanded as required. In addition, if an analysis terminates unsuccessfully, as occasionally happens, the timetrace output is of limited use in determining why. For this reason, you mighty typically use the timetrace output option in the later stages of analysing a stable model, typically in long regular wave or random sea analyses.
Another application of timetrace output is the area of time domain fatigue analysis. When performing a fatigue analysis in Flexcom, the first step would be to perform a random sea analysis for each fatigue seastate. In setting up each analysis, you must store time histories of axial force, Y bending moment and Z bending moment at each location (hot spot) of interest. Earlier versions of Flexcom required these parameters be stored via timetrace output, so there is in a sense a historical link between timetrace output and fatigue analysis in Flexcom. However, more recent versions also allow you to store the axial force and bending moment data using the more widely used database output, so the importance of timetrace output in the overall context of Flexcom has greatly diminished.
One final point to note is that you can request the storage of any time history of interest. The most common application is probably the storage of axial force and bending moment as mentioned above, but it is not confined to those two. In this respect, LifeTime (which is described in Time Domain Fatigue Analysis) may also be used as a general cycle counting tool. The input in this case is typically a random time history generated from random sea analysis timetrace output. However you can use LifeTime to cycle count any time history data organised in a format which mimics the Flexcom timetrace output format. The cycle counting output is presented in terms of response histograms.
•*TIMETRACE is used to request the storage of results for timetrace postprocessing (this is mainly used in the area of time domain fatigue analysis).