Centering diagonals vs centering connection gussets

[MonsieurR]

Hi all,

I'm currently learning connections and I would like to debate how does one design the bracing connections in terms of centering to the beams and columns;

Initially I would thought that centering the gusset plate would be better for symmetry of the anchor bolts or beam bolts (see attachment on right), but in practice I have seen people centering the diagonal to the column and leaving the gusset plate eccentric to the column (see attachment on left), which makes more sense for the analysis, since this was made as that.

I'm currently more inclined to the right option because the eccentricity is small for the columns and beams and I'm somehow tight in this particular connection.

What do you think about it? Do you have any preference?

Best regards.

 

[KootK]

I prefer to leave the beam centered and offset the gusset. If you center the gusset and offset the beam, there's still eccentricity in the system, it's just a different eccentricity (the beam is what delivers the load after all).

At the end of the day, I don't feel that the minor eccentricity matters much from a technical perspective. We're assembling buildings here, not pianos. And I think it would be awkward to try have all your beams offset that tiny amount, particularly if that amount is changing in different situations.


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.

 

[MGaMart]

Offset the connection material. The primary structure should not conform to its connection, rather the other way around. This is especially true with perimeter beams where offsetting the beam can have major consequences on cladding details. In regards to bracing and the location of gussets, it depends on the bracing type. If it's a single sided connection to the gusset, you may want to have both gusset and brace offset so the faying surface is on centerline of the beam/column. Double sided brace connections, the gusset could obviously be centred. Typically, the minor eccentricity formed can often be ignored (except in the case of compression loading for single sided bracing connections).

 

[DETstru]

I agree with the above. Offset the gusset.

One typically designs the brace for eccentric connecting material, but not the column/beam it's connected to.
For example, see Table 4-12 in the AISC manual, which accounts for eccentric loading due to the offset gusset on an angle shape.