Discussion Groups

Robot Structural Analysis

Reply
Valued Contributor
mortel09
Posts: 56
Registered: ‎01-31-2012
Accepted Solution

lifting the construction

836 Views, 64 Replies
04-19-2012 04:16 AM

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?

Please use plain text.
Valued Mentor
tony.ridley
Posts: 652
Registered: ‎09-07-2011

Re: lifting the construction

04-19-2012 04:35 AM 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

Please use plain text.
Product Support
Rafal.Gaweda
Posts: 5,048
Registered: ‎04-26-2010

Re: lifting the construction

04-19-2012 04:44 AM in reply to: tony.ridley

Kudos for you Tony :-)



Rafal Gaweda
Please use plain text.
Valued Contributor
mortel09
Posts: 56
Registered: ‎01-31-2012

Re: lifting the construction

04-19-2012 04:54 AM 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....

Please use plain text.
Valued Mentor
tony.ridley
Posts: 652
Registered: ‎09-07-2011

Re: lifting the construction

04-19-2012 05:01 AM 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?  

 

 

Please use plain text.
Valued Contributor
mortel09
Posts: 56
Registered: ‎01-31-2012

Re: lifting the construction

04-19-2012 05:05 AM 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... 

Please use plain text.
Valued Mentor
tony.ridley
Posts: 652
Registered: ‎09-07-2011

Re: lifting the construction

04-19-2012 05:23 AM 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

Please use plain text.
Valued Contributor
mortel09
Posts: 56
Registered: ‎01-31-2012

Re: lifting the construction

04-19-2012 05:36 AM 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 ?

Please use plain text.
Valued Mentor
tony.ridley
Posts: 652
Registered: ‎09-07-2011

Re: lifting the construction

04-19-2012 06:00 AM 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.  
 

Please use plain text.
Valued Contributor
mortel09
Posts: 56
Registered: ‎01-31-2012

Re: lifting the construction

04-19-2012 06:05 AM 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

Please use plain text.