## Robot Structural Analysis

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# Re: lifting the construction

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Why am I not able to sent attachements?

# Re: lifting the construction

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Have you ziped the file? right click on it and 7-zip it to "filename.zip"

# Re: lifting the construction

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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?

# Re: lifting the construction

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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

# Re: lifting the construction

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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?????

# Re: lifting the construction

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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.

# Re: lifting the construction

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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.

# Re: lifting the construction

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The tipoc is still unsolved? I need to calculate similar structure... : )

# Re: lifting the construction

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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.*

**Artur Kosakowski**

# Re: lifting the construction

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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