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
Solved! Go to Solution.
Solved by CKDDIZ. Go to Solution.
Solved by Artur.Kosakowski. Go to Solution.
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
Rafael Medeiros
Did you find this post helpful? Feel free to Like this post.
Did your question get successfully answered? Then click on the ACCEPT SOLUTION button.
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!!
Delete the side posts and replace them with the columns.
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
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.
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
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.
Is there an option in RSA, example 2 bars to be connected as 1?
Vote here : http://forums.autodesk.com/t5/Robot-Structural-Analysis/Merging-two-bars-into-one-bar/idi-p/3701596
Do you mean
http://forums.autodesk.com/t5/Autodesk-Robot-Structural/Joining-bars-in-RSA2013/m-p/3567934
or
Can you please show step by step what changes did you do to the 3d model, 😞
I see, you applied pinned-pinned releases to the purlins, what else?
The chords must be continuous or use partial releases, but I don't see in the model you applied partial releases to the chords!!
Can you please show step by step what changes did you do to the 3d model, 😞
I see, you applied pinned-pinned releases to the purlins, what else?
No, actually they were already defined in the model you sent
The chords must be continuous
therefore I deleted truss bar attribute from them
or use partial releases, but I don't see in the model you applied partial releases to the chords!!
That was just the suggestion which you can take or reject. This depends on the expected behavior of the truss node connections and the final decision is in your hand.
See http://forums.autodesk.com/t5/Autodesk-Robot-Structural/Uniform-planar-load-on-contour/m-p/3030154 (post 4).