Autodesk Robot Structural Analysis

[#1]

hello,

my question is related to truss design,when the moment release is applied to the truss member during calculations the instability window appears!!! Why does this happen?

Thanks

[#2]

You shouldn´t apply releases to the members that have a pinned support as one of their nodes.

Also ,Instead of using releases you can use "truss bars  only" through geometry/additonal atributes/advanced properties

[#3]

I tryed to model an example from the truss database selection on two fixed columns, the truss members are moment realesed from the truss table option.

Still got the stability window during calcs!! 

[#4 · Accepted solution]

Delete the side posts and replace them with the columns.

[#5]

Hi,

calculated a truss in 2D in truss structure type (pic 1), exporting it in 3D ( pic 2) getting instability in Y dir.

Suggestions please!

Thank you

[#6]

If you have out of truss plane releases nothing prevent horizontal movement of its elements in this direction. I think you should add some boundary conditions (or redefine the releases) to prevent this from happening.

[#7]

1) using the truss bar option without any bar release, getting the same instability type.

2) using bar release in X,Z direction only , same instability.

Trying to solve the roof structure in 3D, how important is the bar offset of the transversal beams (purlins) in this case?

Do you recommend roof as cladding, and wind load applied on it?

Thanks

[#8]

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1) using the truss bar option without any bar release, getting the same instability type.

Truss bars are similar to bars with pinned end connections.

2) using bar release in X,Z direction only , same instability.

For a 3D structural roof you should keep the chords as continuous (see the attached model). Otherwise you can consider use of partial releases.

Trying to solve the roof structure in 3D, how important is the bar offset of the transversal beams (purlins) in this case?

 Personally I would not define any offsets.

Do you recommend roof as cladding, and wind load applied on it?

This is one of the options but this is going to be your decision

P.S. I have corrected the error of not applying truss bar attribute to one line of posts in the attached model too.

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[#9]

Thanks

[#10]

Is there an option in RSA, example 2 bars to be connected as 1?