Is it possible to statically model a BODY being ballasted down, interact with the seabed and then ballasted over onto the seabed? I have tried modeling the seabed as an -OBSTACLE (similar to QUAY example), but it seems that as I add ballast to the BODY, that the -OBSTACLE moves with the body once using &EQUI command. Can the seabed be modeled as an -OBSTACLE (FIXED), but have the body statically be determined without affecting the -OBSTACLE? Or can this only be determined in Time Domain?
I also know you can fix DZ, but as the BODY is tipped over, I need it to pivot on it's edge which which is in contact with the seabed, not about it's origin.
Could you model the seabed as a fixed plate that has interaction with the BODY once in contact?
Lastly, I have seen the possibility of modeling the seabed as a "FOUNDATION"? Isn't this a connector and how is it applied to a certain depth or to the body when a certain draft is reached?
I thank you in advance for any help and wish you the best!
Regards,Scott
HI Scott,
Is this for a float-off / float-on?
Connection between the vessel and the seabed are usually modeled with GSPRs. There should be a node of the vessel where the spring is going to provide support. This simulation is usually done from the sitting on bottom to floating position. Even if in real life the sequence is ballast down. The reason the sequence is from sitting on bottom to floating position is because it makes placing the springs easier.
You can always define the event is reverse. I mean when you store an event you can count backwards.
What is your experience with MOSES? Should I provide more details?
There is a SIG next week. The analysis in the SIG starts with a vessel on the seabed. Have you received an invitation? Please see the Bentley events.
I hope this helps.
Georgina Maldonado
Hello Georgina,
Thanks for the quick reply!
After looking into the GSPR I have a questions (using generic values below):
If I have a water depth of 622 ft; how does the GSPR know to only work once the BODY reaches a draft of 622 ft?
It seems that I can achieve drafts greater than 622 ft...any insight?
Also what is the date and title of the SIG next week?
Regards,
Scott
&env -depth 622$$*************************************************************************************
MEDIT &describe body OMITTED *T1 0 0 0 &type T1 &point(coord *T1 -g) &set T1 = &point(coord *T1 -g) ~fix GSPR TENSION Z 999999 1000000000 -len 0END_MEDIT
Hi Scott,
Making the assumption that you are doing this in reverse (as suggested yesterday).
The gspr element should be placed on the seabed. Strong axis facing up. It should be a compression element. Make the stiffness large enough to hold the weight of the vessel.
When you start to deballast the springs will let got.
Try the link below to learn more about the SIG.
https://gateway.on24.com/wcc/eh/2028083/lp/2265835/sig-workshop:-bentley-offshore-–-righting-a-capsized-vessel-with-moses/?_ga=2.217343126.1862941133.1586436458-2012526545.1530035434
Thank you for the help and the link.
My last question is how does the GSPR element get placed on the seabed? I thought only -ANCHOR could only be used with ROD or B_CAT class connectors?
Regards,Scott Carnley
You have to define a node in the body = ground system. Put one end of the GSPR on that ground node. Put the other node on the vessel. MOSES will measure the distance between the two nodes. If you use a length of zero, then MOSES will turn off the GSPR compression element. Please see the "spring" sample in the below directory.
C:\Program Files\Bentley\Engineering\MOSES CONNECT Edition V11\hdesk\runs\tests\conn
I have watched the webinar multiple times, but I was wondering if it is possible to obtain a copy of the .CIF and .DAT file used in the webinar to get a better understanding of how the GSPR elements are modeled. I am able to model the GSPR myself, but I am not trusting I have done it properly
Can you contact me via personal email?
georgina.maldonado@bentley.com
thank you,
georgina