Horizontal bracing to web connection

[BAGW]

Hi,

I have a question regarding horizontal brace attached to beam web with a welded gusset plate connection. See image below. In such connections, do the plate and weld need to be checked for the eccentricity from the bolts to the weld? If yes, can I assume the eccentric moment will be resisted by plate and do the beam check for just the shear force along the web?

 

[canwesteng]

IME, the eccentricity is accounted for in the brace. For angles connected to a gusset I believe it's baked into the AISC equations, for HSS braces the braces could be slightly offset, and for WT braces you already have a bunch of eccentricity to account for.

 

[BAGW]

I have never designed the braces for the eccentricity forces. Always incorporated in the connection. This can be viewed as a column braces connection correct? And use UFM to resolve the forces?

Feels like the Hb component that results from the brace force, the web needs to be checked for it.

 

[canwesteng]

Ah sorry, I misunderstood. I thought out of plane eccentricity. I would use KISS method here, I think it can be resolve into shears and tensions only at the web, but the UFM method is also valid. If you do get a resulting moment, the weld and the plate should be designed for it, but it shouldn't be making the gusset work too hard.

 

[BAGW]

To keep it simple, lets say KISS method is being used. Should I consider the eccentricity form the bolts to line of weld for connection design? Does not seem like it. But having tough time to prove it to myself

 

[canwesteng]

Here's an ugly sketch, making some assumptions on the force in the braces. Take sum of moments about the work point and you'll see there is no moment though. If you put the work point in the gusset and not at the web, then it's different.

 

[BAGW]

Thank you.

 

[human909]

I have a question regarding horizontal brace attached to beam web with a welded gusset plate connection. See image below. In such connections, do the plate and weld need to be checked for the eccentricity from the bolts to the weld? If yes, can I assume the eccentric moment will be resisted by plate and do the beam check for just the shear force along the web?

I would not considerer the eccentricity the web as:
1. The eccentricity is extremely minor compared to the member size.
2. The column and web is not very stiff under eccentric loads would twist and relieve the loads, the other members don't have that opportunity as they are quite stiff (until they buckle.)

Regarding the gusset and the angles. Absolutely I'd check both for the influence of eccentricity. The gusset if proportioned corrected isn't a big deal but it is a big deal for the angles under compression.