How can i simulate that the construction is getting lifted in robot. The construction i have build is going to be lifted onto an oil rig. how do i simulate this in robot?
Solved! Go to Solution.
Solved by Rafacascudo. Go to Solution.
Solved by Rafal.Gaweda. Go to Solution.
Iam not sure if its okei or not. You can look at the file that i attached earlier.
yeah, I see it now. Whats your opinion of what i should do? If i added a Support in node 1 (RX, RY and RZ) i get as good as zero. Would this be the proper way of doing it?
Rafael Medeiros
Did you find this post helpful? Feel free to Like this post.
Did your question get successfully answered? Then click on the ACCEPT SOLUTION button.
After we put the soft springs in each of the four corners we still get a wierd reading in the displacements bar under node properties.
See attachment.
I put the springs to 100 kN/m and got rid of the displacements, dont know if thats the best solution. The reactions in the springs is still very low..
as I said before " your lifting point coordinates (node 71) should be as precise as the CG of the loads on your lifting load case/combination"
This will not work with several load cases.For each load case you should have a unique lifting support type(UX + coordinates) according to the lifting point coordinates.
If the lifting point coordinates doesn´t match the Loads CG , the sum of the cables horizontal components will not be zero and as consequence you´ll get horizontal reactions on the XY supports and large displacements on the structure nodes
Rafael Medeiros
Did you find this post helpful? Feel free to Like this post.
Did your question get successfully answered? Then click on the ACCEPT SOLUTION button.
Hei!
Just downloaded the model and playd with it a little. I did have to place fixed supports at the end og the cables, forcing them to get some moments but placed an release at the connection to the main struture so that the moments wont travel further into the structure. I have not been using Robot for a long time so this may be total fail but this way I think the axial forces from the cables with there angle towards center of gravity will be taken into account without playing with supports at each corner
Its not working....arrrgggg....I did compress it to .rar file, attached it and when I click on "post" the attachment dissapears and no post sent. Any Idea what might be the problem?
It dos'nt support .rar file. You need to make it a .zip file or any of the other file type that this forum support, see the attachment
Sorry but I still cant send the file. Maby its the security insallation on my computer. I will send my model tomorrow.
But despite of me not being able to send the model, my instict tellls me that modelling the cables instead of manipulatin the supports is the right thing to do. Why?? because it will take a long time predicing how to define the supports. How can you place a support in these corners knowing how they will react in reality?????
Do you need to modell the cabels? Editing a support dos'nt take much time. adding a support in each corner with only Ux checked i think is the right way.
As I understand this problem, due to angle that the cables will form from the support to senter of gravity there will be axial forces acting on the frames. Applying a support that only Ux checked you wont be taking these forces into the calculations. And you get warning of unstable constuction.....
So there for I think modelling the cables gives you the correct picture of how this modell will react.
I have made a test model and tried to iterate the position of the support till the moment the values of bending moments is small enough to be neglected. Basically I started with step a and then I adjusted the support position moving it according to the values obtained from the reactions:
x movement = MY / FZ
y movement = MX/ FZ
You may want to exclude rods from self-weight loads.
If you find your post answered press the Accept as Solution button please. This will help other users to find solutions much faster. Thank you.
Here is a similar lifting problem, but with 2 levels of slings.
Check it out and comment it if you like.
The above suggested approach was used: moved the top support (pinned), then calculation, again moving, again calculation and so on, until minimum dispacements found.
On the base there are 2 UX and 2 UY blocked.
The load case intended for verification is DWNet.
DWLift is DWNet x 2
The other load cases don't quite work, because the loads they apply move the center of gravity somewhere else.
So it would be another equilibrium geometry for each of them.
How close to reality do you consider this model to be?
Download if from here http://www.fileshare.ro/e29427221
Thanks
Can't find what you're looking for? Ask the community or share your knowledge.