Truss Work Point (EBF)

[STR04]

Has anyone ever designed built-up truss with an offset at the nodes where the diagonals and verticals meet at the chords? I have an 80' truss on a 6:12 slope built with double angles for diagonals/verticals and WT's for chords. The work point does not align at the member centerlines because of geometry restraints. To simplify the fabrication I want to eliminate adding gusset plates. My connection now resembles an EBF with induced moments. If I save on fabrication cost by increasing the chord size and eliminating the addition of welded plates, does anyone see a problem with that?
TIA

 

[14159]

I think you'll have to get with your EOR about this one to see if they are afraid of these induced moments and shears. After all, they are responsible for the member design. Sometimes it can be significant, but often it's not. I don't like your odds because most EORs will say "no" before either going out on a limb and just saying "yes" or actually looking at their truss models to see if it's ok. It is still worth giving them a call. Perhaps you'll get lucky.

DBD

 

[jike]

We typically offset the members for trusses made from tubes or pipes to reduce the fabrication cost. I am sure it can be done for other types of trusses but it will depend upon the amount of the offset and how much bending it induces in the chords. You need to model this on the computer and make sure the chords are not overstressed.

 

[STR04]

I am the EOR for this one. I used STAAD to model my truss and built 6" offsets at the nodes. I do not design trusses everyday but like to value engineer my designs when possible.

 

[14159]

STR04 said: "I am the EOR for this one...."

That is the first time I've ever seen this happen around here! I'm just glad the original poster didn't say anything nasty about the EOR!

DBD

 

[transmissiontowers]

I'm not familiar with Staad (GTStrudl user) but can you switch the truss members to beam elements and have Staad check the members as beams? If you assume the diag and vert members as beams due to fixed end connections to the WT chords, you should see the maximum moments induced due to eccentricities.

_____________________________________
I have been called "A storehouse of worthless information" many times.

 

[dbuzz]

I should think that a thickener chord member would be preferable to stiffening all the nodes.

 

[STR04]

DBDAVIS,

What's to be said that is nasty? Are we not professional or do we alter our egos when entering chat rooms? Am I the only EOR around here?

STR04