Steel Roof Truss

[IUD]

Hi I am designing a steel roof truss for the community building . In the roof truss, I have to use 16mm as the thickness of the gusset plate. i need to check buckling out-of-the-plane of the truss. if anyone can give an idea ho to do this , its really helpful. Thanks

 

[jayrod12]

The truss itself is essentially a giant beam with a moment of inertia (and therefore a bending modulus). Design it the same way as a beam for out of plane bucking.

I would assume this truss has some form of roof trusses/joists framing into it. Therefore it's likely the top chord will be adequately braced by this. You should provide bottom chord bridging to ensure the bottom chord does exceed slenderness requirements for elements in tension (or compression if you are expecting there to be load reversal).

Once you have provided the bracing for the top and bottom chords as indicated above, I'd bet buckling is a non-issue for the truss as a whole.

 

[KootK]

We're talking about buckling of the gusset plates themselves right? If so:

1) Use the Whitmore section concept to work out an effective width of the effective "column" within the gusset.

2) Determine the length of your effective column as the distance between points of rotational restraint at the connected members. Some folks use K = 1.0; others K = 0.7.

3) Design the effective column within the gusset using the usual AISC provisions for compression members.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[Guest262653]

If you're using European Standards, the SCI released an update of their guide for simple connections (SCI P358). They present guidance in sections 8.4 and 8.5 for the design of gusset plates in bracing connections, including their stability. There's also an online calculator that uses the yield line model presented in the guide. Check [URL unfurl="true"]http://bcsatools.steel-sci.org/GussetPlateDesigner/GussetPlateTool.html[/url]

The guide can be found for free at www.steelconstruction.info/File:SCI_P358.pdf?internal_link

 

[KootK]

That's great stuff avs, thank you for sharing it. I'm feeling more like being European all the time.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[Guest262653]

You're welcome KootK. Trying to give back in some way all the stuff I've been learning around here, especially from your posts!
It's great being European, that is, if you like navigating the thousands of pages and cross-references of the Eurocodes and their NDP's...