Hello! I am analyzing a Jack Up Rig with a single column for wet tow. During wet tow, the jack-up will be floating on its hull and the column will be above water.
The procedure I have adopted is as follows:
1. Perform a wave dynamic analysis in SACS Motions module to calculate the response of the structure. The cargo for the analysis is the column and the vessel is the hull of my jack-up. I have already designed the hull in maxsurf and placed the file in (both .msd and .hmd) inside the SACS vessel library.
2. Use the response file as an input to SACS Tow module to run tow analysis in order to check the strength of the column.
3. Perform linear static analysis with the generated static loads in tow analysis with other loads.
Problem:
Every time I run the motion analysis, it gives an error stating "VESSEL ID NOT FOUND IN THE LIBRARY".
Please let me know if my procedure is correct and also how do I resolve the above issue.
Thanks in advance.
There are two ways that you can run Motions analysis in SACS. You can either use the SACS Motions program or the SACS Motions/Stability module.
Since you have created the hull in maxsurf, I would recommend using the SACS Motions program to run the motions analysis. You can open the MSD file in SACS Motions, add your column as cargo and then perform the motions analysis to generate your motions results. You can then use the SACS -> Export -> SACS Tow File feature to generate a tow input file which can then be used to perform your tow analysis on the column in SACS.
The alternative method would be to perform the motions analysis using the Motions/Stability module, but that would require you define the hull in the transportation input file or use one of the vessels from the vessel library.
I would recommend referring to the SACS Motions and SACS Motions/Stability manuals for more information.
Hi Geoff,
Thank you for understanding my problem and for such a detailed explanation. As per your recommendation I am using SACS Motions Module to compute the response of my structure.
Here is the progress so far:
1. Performed SACS Motions analysis for 3 wave headings i.e. 90, 135 and 180 degrees.
2. Exported the SACS Tow File which lists the Motions RAOs for different wave periods.
The exported file also contains load cases such as LCRAO R+I, with both real and imaginary parts. This generates two load cases (real and imaginary) for each rao line. I checked the tow manual which states that this procedure is used for Fatigue Analysis. How do I use this method to perform my tow analysis on the column in SACS?
The tow manual also mentions use of WAVDEF card which also creates wave inertia loading on the column for each of the number of points mentioned in a wave cycle. I am not aware of the function of these points. Is it to specify the phase of the incident waves on the structure? How do I use this method to perform my tow analysis on the column in SACS?
Thanks again,
Siddhant
Siddhant,
There are two options that you have to generate static load cases for Tow analyses:
Regards,
Geoff
Answer Verified By: Sid