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Valued Contributor
CKDDIZ
Posts: 80
Registered: ‎05-29-2012
Accepted Solution

truss design

1545 Views, 17 Replies
08-27-2012 06:19 AM

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

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Valued Mentor
Rafacascudo
Posts: 264
Registered: ‎05-16-2011

Re: truss design

08-27-2012 06:32 AM in reply to: CKDDIZ

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

 

 

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Valued Contributor
CKDDIZ
Posts: 80
Registered: ‎05-29-2012

Re: truss design

08-27-2012 07:24 AM in reply to: Rafacascudo

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!! 

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Product Support
Artur.Kosakowski
Posts: 4,962
Registered: ‎12-17-2010

Re: truss design

08-27-2012 07:40 AM in reply to: CKDDIZ

Delete the side posts and replace them with the columns.



Artur Kosakowski
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Valued Contributor
CKDDIZ
Posts: 80
Registered: ‎05-29-2012

Re: truss design

01-08-2013 01:22 AM in reply to: Artur.Kosakowski

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

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Product Support
Artur.Kosakowski
Posts: 4,962
Registered: ‎12-17-2010

Re: truss design

01-08-2013 01:54 AM in reply to: CKDDIZ

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.



Artur Kosakowski
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Valued Contributor
CKDDIZ
Posts: 80
Registered: ‎05-29-2012

Re: truss design

01-08-2013 04:57 AM in reply to: Artur.Kosakowski

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

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Product Support
Artur.Kosakowski
Posts: 4,962
Registered: ‎12-17-2010

Re: truss design

01-08-2013 05:11 AM in reply to: CKDDIZ


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.

 

partial releases.PNG

 

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 :smileyhappy:

 

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


 



Artur Kosakowski
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Valued Contributor
CKDDIZ
Posts: 80
Registered: ‎05-29-2012

Re: truss design

01-08-2013 05:47 AM in reply to: Artur.Kosakowski

Thanks :smileywink:

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Valued Contributor
CKDDIZ
Posts: 80
Registered: ‎05-29-2012

Re: truss design

01-08-2013 06:05 AM in reply to: CKDDIZ

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

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