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lifting the construction

93 REPLIES 93
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Message 1 of 94
mortel09
6060 Views, 93 Replies

lifting the construction

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?

93 REPLIES 93
Message 21 of 94
Rafal.Gaweda
in reply to: mortel09

This was example how to properly rotate support. 

As Rafacascudo said :  "No ,just Ux ,as long as you set the support local direction like I recommended"



Rafal Gaweda
Message 22 of 94
mortel09
in reply to: Rafal.Gaweda

why exactly just ux?

Message 23 of 94
Rafacascudo
in reply to: tony.ridley

Hi Tony, If you have a small free height to lift the structure ,the angle the cable will do with the horizontal will be smaller and the horizontal forces can be very significant! For example if you have an 45 degrees angle(which is not rare) ,horizontal forces will be equal to the vertical force lifted on that point. Anyway , even if the angles are closer to 90 degrees, I believe this is the exact solution for the problem. Hard work?? I´m pretty sure an user as well skilled as you can set these supports in less than 30 secs!! And it is a fun solution!! If you change the lifting point coordinates ,you´ll will notice the 4 supports automatically pointing toward that single lift point/node. 😉


Rafael Medeiros
Robot Structural Analysis

Message 24 of 94
tony.ridley
in reply to: Rafacascudo

Agree with your thoughts.  However I'm lazy sometimes 😞

Actually though, we normally add another member to the system, called a "spreader"  The additional beam takes a compressive force, and leaves the actual structure to be picked up with a vertical force only.  

 

I can send you a picture if you're not sure what it is.  

 

Tony

 

 

Message 25 of 94
mortel09
in reply to: tony.ridley

i would like a picture plz Smiley Happy

Message 26 of 94
mortel09
in reply to: Rafal.Gaweda

When i calculate the file after i have added the supports on each corner I get a warning of instability on node 52... see the attached file. Should i take this to consideration or is it nothing to worry about?

Message 27 of 94
tony.ridley
in reply to: mortel09

can you post the model?

 

Message 28 of 94
mortel09
in reply to: tony.ridley

there

Message 29 of 94
tony.ridley
in reply to: mortel09

model attached

 

 

Message 30 of 94
mortel09
in reply to: Rafal.Gaweda

Why should I only cross off on the UX, and not UY? I attached my file, could you see if it looks like iam simulating a lift?

Message 31 of 94
tony.ridley
in reply to: mortel09

normally, just use the spreader on two sides, it will be stable for regular shaped geometry.  

 

 

Message 32 of 94
mortel09
in reply to: tony.ridley

we are not supposed to use spreader bars, but we have added a support in one of the corner were we have cross checked RX, RY and RZ. This worked with the instabilty in node 52 😉

Message 33 of 94
Rafacascudo
in reply to: mortel09

Mortel09 ,No instabilities on your original model if you use the multi-threaded solver.


Rafael Medeiros
Robot Structural Analysis

Message 34 of 94
mortel09
in reply to: Rafacascudo

the multi-threaded solver? I added a support in on of the corner so hold the rotation (RX, RY and RZ), will this be wrong to do?

Message 35 of 94
tony.ridley
in reply to: mortel09

My opinion is that if you have an instability in a model, using multi threaded to avoid it is un-conservative and not recommended.  The model should run fine on automatic before switching to multi thread. 

Message 36 of 94
Rafal.Gaweda
in reply to: tony.ridley

Multithreaded solver may not report instabilities that's why it is recommended to find all model instabilities (esspecially of type 1 and 2) using different solvers.



Rafal Gaweda
Message 37 of 94
mortel09
in reply to: Rafal.Gaweda

Iam not sure what to do, I attached the file, when you hit calculations you get a warning of instability in node 52. What should i do?

Message 38 of 94
tony.ridley
in reply to: mortel09

it's type 3, so may just be large differernce in stiffness.  

Message 39 of 94
mortel09
in reply to: tony.ridley

Okei, thanks alot guys. The both of you have been really helpfull. I appreciate your help.

Message 40 of 94
Artur.Kosakowski
in reply to: mortel09

Please check the displacements and rotations for case 1 (self-weight) before ignoring the reported instability.



Artur Kosakowski

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