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Sesam – HydroD/Wadam workshop Load transfer analysis
Sesam User Course – HydroD Wadam Workshop 2: Hydrodynamic load transfer analysis of a semisubmersible
This workshop is based on the following models created by GeniE: - Panel model – T1.FEM - Morison model – T2.FEM - Structural (FE) model & Mass Model – T3.FEM (Analysis 2 only) - The models are found on the given training course CD/memory stick or here:
C:\Program Files\DNVS\HydroD V4.5-08\Examples\SemisubWadam The model with its main dimensions is shown below. Note: All models will be translated -13 m in z direction The workshop may be performed from Brix Explorer of from HydroD directly
Sesam – HydroD/Wadam workshop Load transfer analysis
In this workshop we will use a new Wadam wizard Start HydroD and re-open the previous workspace (may done from Brix Explorer for Sesam). Start the Wadam wizard by clicking the button: Start by selecting the Composite Model and read the information provided in the Information
tab as shown below.
Then go to the Settings tab and enter data as shown to the right.
Click OK to proceed with the wizard.
Note that the first 8 steps for the environment may be skipped (to re-use the data from the first run).
Sesam – HydroD/Wadam workshop Load transfer analysis
and in the Create/Edit Direction dialog enter the values 0, 90 and 15 in the first three fields. When clicking ‘Fill table’ seven directions are filled into the table.
Click Apply followed by Cancel to proceed with the wizard.
Frequency set
Click the ‘Next step’ button. Select Period, enter the values 4, 38 and 2 and click
Fill table. Click Apply followed by
Cancel to proceed with the wizard.
May be skipped
Sesam – HydroD/Wadam workshop Load transfer analysis
Frequency domain condition A frequency domain condition is created by
selecting a previously defined direction set and frequency set.
The wave amplitude is not used for a Wadam analysis
Sea state Give data as shown for the sea state: Sea state
duration is 3 hours. Select spreading function and main heading by clicking the down-arrows next to the fields. Select a previously defined wave spectrum by clicking in the field and see that a down-arrow appears allowing the spectrum to be chosen. Notice the help text when positioning the mouse over the column header in the table.
May be skipped
Sesam – HydroD/Wadam workshop Load transfer analysis
Include the static load, if wanted Specify first load case as 1 NOTE: Composite model load transfer can be done in two different ways, by using a
superelement structural model (several superelements) or by using a single superelement model
- When using the (several) superelement option, the Morison model should be included in the structural model as a separate superelement, meaning the structural model needs to be a superelement model consisting of a shell part and a beam (bracings) part, in two different T#.fem files coupled together at a top level. This workshop has a separate Morison superelement, but this is not included in the structural model. Consequently, the Morison loads will not be included in the structural analysis.
- When using the single superelement composite model, the complete structural model, including bracings etc., should be used also as the Morison model in HydroD. This is not the case in this workshop, but it may be achieved by replacing T2.FEM by T3.FEM and define the correct Morison sections.
Yes/No to Static load
Sesam – HydroD/Wadam workshop Load transfer analysis
Analysis Clicking the Last step button of the wizard opens
the dialog for running Wadam. Or, run the Wadam analysis by selecting WadamRun2in the dialog below to the right
Deselect WadamRun1. Start WadamRun2. See print file as shown below to the right. If you have closed the dialog reopen it as shown to the right.
The print-out from Wadam should be checked with respect to, among other things, any warnings or errors and model properties such as mass and buoyancy data and motion characteristics.
The bottom line should read: P R O G R A M N O R M A L E N D
The result files are located in the WadamRun1 directory in the current workspace - Important files
After a successful Wadam run, the next typical steps are to use the postprocessors Postresp – for statistical results – and Xtract – for animation of motions and wave load pressure
Sesam – HydroD/Wadam workshop Load transfer analysis
It is useful to verify the model and wave loads prior to the structural analysis
To start Xtract just right-click the WadamRun2 folder and select Xtract.
In Xtract, Double-click Toplevel in the Database view to view the model
- The model file T3.FEM, including the load file L3.FEM, and the Wadam result file, G1.sif, will be opened automatically
- Double-click Toplevel in the Database view to view the model
Some typical commands are: - Go to Resultcases at the bottom of the Database
view, select e.g. no. 5 - Double-click Elements – Surface loads – Normal pressure - Use ‘Display – Part Attributes’ to set the sea surface
transparent, remove contours and add mesh - Select ‘Model – Deformed’ and set ‘Model – Deformation Scaling’ to 5 (e.g.) - Go to ‘Animation – Frequency animation’. Use defaults. - Start the animation by selecting the ‘Play’ button - Zoom into the model - Rotate the model by with the right mouse button - Other buttons to frame the model and select views
If time allows, you should try out more features of Xtract
Run Xtract from HydroD
Sesam – HydroD/Wadam workshop Load transfer analysis
From the HydroD version 4.2-04, Sestra may be started directly from within HydroD - To run Sestra, just right-click the WadamRun2 folder and select Sestra - Sestra will automatically read the load file, L3.fem, and the S3.fem file.
Run Sestra from HydroD
This run of Sestra will produce the following files: - SESTRA.LIS Print-out from Sestra - FOR007 Additional file from Sestra, used primarily when an error is found
Otherwise called SESTRA.MNT - R3.SIN Results file
The print-out (SESTRA.LIS ) should be checked, especially with respect to sum of loads and
masses and reaction forces. The results file, R3.SIN, may be read into Xtract for further postprocessing.