Output Categories |
 
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Output Categories |
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This section provides a summary of the postprocessing request options available in terms of database postprocessing. Results can be requested in five basic categories – Timetrace, Snapshot, Statistics, Spectrum and RAO. Additional facilities are available to define Element Sets, Axes & Vectors and parameters relating to the calculation of Extreme Values. The following is a summary of each category.
The aim of the Standard Output option is to allow you to quickly request a summary of pertinent information, without the inconvenience of explicitly requesting specific outputs. This facility automates many of the (admittedly minor) tasks which you would otherwise undertake manually. For every element set referenced, Flexcom produces outputs of effective tension, resultant bending moment and von Mises stress for that set. The element set entry is also optional, and if no element sets are listed, it is assumed that output is required for all elements (i.e. element set All). For static and quasi-static analyses, snapshot plots are presented at the last solution time step. For dynamic analyses, statistical plots are created – envelopes in the case of the regular wave analyses, and extreme value plots for random sea analyses. Statistics are measured over the last two wave periods for regular wave analyses, and initial transients are automatically excluded from random sea analysis postprocessing. Given that these output parameters are rarely examined in base units (e.g. effective tension is normally presented in kN or kips, rather than N or lbf), appropriate scale factors are automatically applied to the outputs
A timetrace is a time history of the variation of a particular parameter throughout an analysis. You can request timetraces under the following headings:
Timetrace Headings
Heading |
Description |
Kinematic |
The response of a node in a particular degree of freedom |
Force |
The restoring force or stress at a point on an element |
Reaction |
The reaction at a restrained node in a particular degree of freedom |
Wave Elevation |
The water surface elevation (calculated at Y=Z=0) |
Time Step |
The time step throughout the analysis |
Element Angles |
The angle between two elements |
Vector Angles |
The angle between an element and a vector |
Axis System Angles |
The angle between an element and an axis system |
Guide Surface Reaction |
The contact reaction at a flat guide surface in a particular degree of freedom |
Zero-Gap Reaction |
The contact reaction at a zero-gap guide in a particular degree of freedom |
Pipe-in-Pipe Reaction |
The contact reaction at a pipe-in-pipe connection in a particular degree of freedom |
Clashing |
The minimum clearance, contact reaction force or clashing impulse between two adjacent lines |
Most of this represents standard finite element output, and the use of the Flexcom facilities is straightforward and usually self-explanatory. Flexcom provides a range of outputs under the general heading of Angles. These outputs are provided both here, in Database Postprocessing, and in Summary Postprocessing. Rather than describe the range of outputs in two sections of the manual, a detailed description is confined to one section only. You are referred to Angles Output for a more detailed discussion of Flexcom angles output.
A snapshot is a plot of the distribution of a particular parameter throughout the structure (or a part of it you specify) at a particular time during the analysis. Flexcom has two snapshot options, namely Motion and Force. Motion requests the distribution of the motion in a global degree of freedom, while Force is available for plotting the distribution of a restoring force or stress.
Options are provided for plotting statistics of motions and forces for specified element sets or the whole structure. Outputs include maximum/minimum envelopes, mean values, standard deviations and extreme values. Extreme values are discussed in further detail in the Extreme Values Section.
The results of a random sea dynamic analysis are usually presented in terms of response spectra, for which Flexcom has four options. These are Motion, Force, Reaction and Elevation. Motion, Force and Reaction have the same meaning as before, while Elevation refers to the water surface elevation at Y=Z=0. This last option is useful for comparing the realised and target wave spectra.
Flexcom provides an option to generate RAO amplitudes and phases for selected output parameters. Specifically, it is possible to obtain RAOs for nodal motions, element forces and stresses, and floating body motions. The procedure followed by the software for the computation of RAOs depends on whether the relevant analysis involved regular or irregular wave loading. Further details are provided in Computation of RAOs.
•Numerous keywords are contained in the $DATABASE POSTPROCESSING section, each of which is capable of generating Graphical Output, Tabular Output and Spreadsheet Output.
o*STANDARD OUTPUT is used to quickly request a selection of commonly used outputs
o*TIMETRACE is used to request the creation of timetrace plots.
o*SNAPSHOT is used to request the creation of snapshot plots.
o*STATISTICS is used to request the creation of statistics plots.
o*SPECTRUM is used to request the creation of spectrum plots.
o*RAO is used to request the creation of RAO plots.
•*OUTPUT FILES is used to specify the types of output file required from database postprocessing.
If you would like to see an example of how these keywords are used in practice, refer to any of the standard Flexcom Examples.