Brace Connection Eccentricity

[dcw815]

I have an HSS brace that's in compression. It is being connected at one end with 2 channels. The channels would be welded to the brace at the four corners of the HSS. Is there an eccentric moment in the channels/HSS from the compressive force? If so, is it M = C x e where 'e' is the distance from the centroid of the HSS to the centroid of the channel? See attached picture.

Thanks.

 

[KootK]

I see no moment in the HSS but slight moments in the channels due to their being loaded off of their centroids. The moment would be half the brace force multiplied by the distance between the channel face and the channel centroid. In reality, this bending is likely resolved by inadvertent fixity to the HSS. I'm assuming that the other ends of the channels are web connected as well.

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.

 

[canwesteng]

I think you're actually loading the channels through the shear center more or less, so not really eccentric, and code equations for compression of channels account for the eccentricity between the centroid and shear centre (at least in CISC)

 

[Hokie93]

I completely agree with KootK's response. There is a good discussion of this very topic in Section 5.9 of "Design of Welded Structures" by Omer W. Blodgett.

 

[dcw815]

Thanks for the responses. At the other end, the channels are riveted to a glulam arch through the channel webs. The arch is a solid section so is there eccentricity there? The load path is from the arch, to the channels, to the HSS.

 

[KootK]

Same answer for the glulam end. A little eccentricity in the channels and none in the glulam.

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.

 

[dcw815]

Perfect. Thanks.