rgr16
Marine/Ocean
- Sep 21, 2013
- 9
Hi!
I have ship-crane system as one rigid body. I calculate 3d disp/vel/acc of every point of ship-crane system for 3h storm using ansys-aqwa and some numerics. Now i need to apply accelerations from crane-ship movements to crane points in FEMAP. I need it for mine beachelor engineergin thesis.
I want to get some function like "stress vs time" with dynamically changing accelerations at crane. Could someone please guide me how to accomplish that?
I was trying to do it on my own, but im stuck now.
At first i wanted to treat that accelerations as some loads at every element of crane and then split m*a=F of each elements equally on its nodes. But i heard that i cant do it that way and i need to perform some vibration analysis with applying accelerations at ship with something like large mass method. Doing example 17.Tower... from FEMAP i find that i may just do direct method in place of LMM.
In femap i only model crane. The modele is as follows. I create some simple crane with 3d tetrahedrons, constraint RX,RY,RZ checked DOFS of bottom surface of crane, connect that constrainted nodes with rigid elements (RBE2 where dependant have checked TX,TY,TZ DOFS) to some independant "base node" below crane. Apply body load of gravity. Apply load at "base node" with function vs frequency. Fixed constraint base node. Then make modal analysis, and frequency/harmonic response analysis from modes. But i do not know what to do next. And dynamics analysis is new thing for me. It would be great if someone make small quide in points what to do, like:
a - bla bla bla
b - ...
c - ...
...
Thanks for any help!
I have ship-crane system as one rigid body. I calculate 3d disp/vel/acc of every point of ship-crane system for 3h storm using ansys-aqwa and some numerics. Now i need to apply accelerations from crane-ship movements to crane points in FEMAP. I need it for mine beachelor engineergin thesis.
I want to get some function like "stress vs time" with dynamically changing accelerations at crane. Could someone please guide me how to accomplish that?
I was trying to do it on my own, but im stuck now.
At first i wanted to treat that accelerations as some loads at every element of crane and then split m*a=F of each elements equally on its nodes. But i heard that i cant do it that way and i need to perform some vibration analysis with applying accelerations at ship with something like large mass method. Doing example 17.Tower... from FEMAP i find that i may just do direct method in place of LMM.
In femap i only model crane. The modele is as follows. I create some simple crane with 3d tetrahedrons, constraint RX,RY,RZ checked DOFS of bottom surface of crane, connect that constrainted nodes with rigid elements (RBE2 where dependant have checked TX,TY,TZ DOFS) to some independant "base node" below crane. Apply body load of gravity. Apply load at "base node" with function vs frequency. Fixed constraint base node. Then make modal analysis, and frequency/harmonic response analysis from modes. But i do not know what to do next. And dynamics analysis is new thing for me. It would be great if someone make small quide in points what to do, like:
a - bla bla bla
b - ...
c - ...
...
Thanks for any help!