Robot Structural Analysis Forum
Welcome to Autodesk’s Robot Structural Analysis Forums. Share your knowledge, ask questions, and explore popular Robot Structural Analysis topics.
cancel
Showing results for 
Show  only  | Search instead for 
Did you mean: 

lifting the construction

93 REPLIES 93
SOLVED
Reply
Message 1 of 94
mortel09
6058 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 2 of 94
tony.ridley
in reply to: mortel09

add pinned support at the lift point, remove usual supports.  add self weight multiplied by a dynamic allowance for lifting.  

 

thats it!

 

tony

Message 3 of 94
Rafal.Gaweda
in reply to: tony.ridley

Kudos for you Tony 🙂



Rafal Gaweda
Message 4 of 94
mortel09
in reply to: tony.ridley

I have done that now, and I have connected the cable from the four corners to the pinned support. but when i calculate I get several warnings about instability in nodes and other warnings. How can I solve this problem? After the calculation the ratio is extremly high....

Message 5 of 94
tony.ridley
in reply to: mortel09

no sorry, I didnt mean add cables and then a single pinned support.  I mean add 4 (or how many you need) pinned supports at the place WHERE THE CABLE IS GOING TO CONNECT.  you don't really need to model the cable, no?  

 

 

Message 6 of 94
mortel09
in reply to: tony.ridley

My construction is going to be lifted at 1 point, so i added a pinned support over center of gravity of the contruction and connected cables from it to the 4 corners... but that didnt work very well... so what you are saying is that i should add 4 supports over center of gravity and then i dont need to pull cables to the corners? 
I dont need to calculate the wire no... 

Message 7 of 94
tony.ridley
in reply to: mortel09

I would not add the support OVER the CG, rather add a support(s) to the BEAM itself at the point(s) where the cable will attach.  Looking at the reactions at each support will tell you if the structure will be stable when it's lifted.

 

Adding a single support for a structure with no rotational restraint can't ever be modelled..

 

 Untitled.png

Message 8 of 94
mortel09
in reply to: tony.ridley

I have attached a pic of what I have done, is this what you mean I should do (supports.png)? I have also attached a pic of how the lift will look like in my mind (supports2.png). Will it calculate the same thing ?

Message 9 of 94
tony.ridley
in reply to: mortel09

Of course, the structure modelled in "supports2" can never work.

It can spin around the support with out ever stopping!

 

So no, it won't calculate the same thing.  
 

Message 10 of 94
mortel09
in reply to: tony.ridley

okei, but if i had added a support that only takes forces from x and y directions in each corner at the bottom of the construction, and made sure that the reactions in the support is very low, so that the construction would not spin, would that be a possible solution? and make the support in top only takes forces in z-direction

Message 11 of 94
tony.ridley
in reply to: mortel09

Perfect!  (well, most likely you will need a lateral support at at least 2 corners)

 

or spring supports..................

 

Message 12 of 94
Rafacascudo
in reply to: mortel09

That´s not true.Forces on the inclined cables will produce horizontal forces on your structure. I would set the supports on the exact direction of the cables.Doing that you won´t need to add any other supports. For creating the " tricky" support ,create a new one fixing de X direction , then click on " direction" and give the coordinates of the point where the 4 cables will join.Then assign this support to your 4 lifting points.Check if they´re on the exact same direction of your cables.


Rafael Medeiros
Robot Structural Analysis

Message 13 of 94
mortel09
in reply to: Rafacascudo

Should all of the "fixed directions" be checked? Like on the pic?

Message 14 of 94
Rafacascudo
in reply to: mortel09

No ,just Ux ,as long as you set the support local direction like I recommended


Rafael Medeiros
Robot Structural Analysis

Message 15 of 94
mortel09
in reply to: Rafacascudo

okei, but dose it look like i have done that according to the piecture i attached?

Message 16 of 94
Rafacascudo
in reply to: mortel09

Yes ,but it looks like the support directions are wrong, probabbly due to the fact you assigned a fixed support for them all


Rafael Medeiros
Robot Structural Analysis

Message 17 of 94
tony.ridley
in reply to: Rafacascudo

Forces on the inclined cables will produce horizontal forces on your structure.

 

Perhaps this is true, but your method seems like a lot of hard work for not much gain.  But each to their own Smiley Happy

Message 18 of 94
mortel09
in reply to: Rafacascudo

okei, ill try that 😉 thx

 

Message 19 of 94
Rafal.Gaweda
in reply to: mortel09

2node.jpg



Rafal Gaweda
Message 20 of 94
mortel09
in reply to: tony.ridley

so now iam suppose to check of UX, UY and UZ? and not only UX?

Can't find what you're looking for? Ask the community or share your knowledge.

Post to forums  

Autodesk Design & Make Report