calculating trussframe

[Peter Telleman]

Hi,

 

In our company we often use trussframes for projection. If I draw a trussframe and attach hoists, it calculates the hoists, but not the structure. Can anyone explain to me why this doesn't work?vertical trussframe.vwx

[Scott C. Parker]

@Peter Telleman I don't have a direct answer other than it's something to do with the modified truss symbols you're using. I played for a while trying to figure out what but I failed. To confirm the calculations would work outright, I built two similar frames using Tomcat and Christie truss. They both calculated as expected. 
Here's the file I played with. Your custom symbols might not match anymore as I was making edits. 
Tomcat is grey as we don't have the structural info. The Christie frame is green as we do have the structural info.
vertical trussframe.vwx

[Peter Telleman]

Hi Scott, thanks a lot for playing with it. I'll look deeper into the symbols we're using, the fact you got it to work with other truss symbols does suggest it has to do with the symbols we're using.

[Peter Telleman]

@Scott C. Parker

Hi, I'm assuming both the Tomcat as the Christie symbols are from the VW library? Are you therefore saying some trusses from the library can be calculated, and some can't?

And why does it work with a "normal" truss length, but not with a frame?

[Scott C. Parker]

Hi Peter,
Yes, my truss were directly from the VW libraries. I confess I didn't seek out the same truss you used from our library during testing. The truss in the drawing you shared has had some custom changes made and I didn't want to mess with them.
All truss in the VW library *should* be able to have some braceworks calculations applied. When we have the structural info from manufacturers, we get more info about flexibility. When we don't, we treat them as static systems. Hence the Grey and Green results.

6 hours ago, Peter Telleman said:

And why does it work with a "normal" truss length, but not with a frame?

I'm not sure what you're asking here. I made frames, and they worked.

[Peter Telleman]

What I think I'm asking is, you've used both Tomcat and Christie truss from the VW Library, and only the Christie was green, therefore my question was, how do we know which truss types in the library work, and which don't? Looking at your file though, even though the Tomcat truss doesn't turn green, it seems to be calculated. So I'm assuming you meant all VW library truss works for the calculations.

I'll speak to the guy who "makes" our truss symbols, because I think he starts with the VW Prolyte symbols, so I'm curious where it goes wrong then.

 

Thanks a lot!

[jcogdell]

@Peter Telleman
The reason why the Christie is green and the Tomcat grey is that Christie has given us the structural data for their trusses and Tomcat refuses to do so. Any truss that doesn't have the structural data is by default set to use the rigid crosssection model. This means that it calculate forces acting on it and passing through it but can't calculate how it reacts to those forces, so no deflection or bending moments for example.

 

I had a look at the symbols and I think the issue is with the 90°corners. I'll dig a little deeper when i get a minute and let you know what I find

[Peter Telleman]

We'd be over the moon if you guys can find out what the issue is.