Horizontal floor bracing 1

[jchi]

I have horizontal floor bracing (grating floor-no diaphragm) to transfer seismic loads to my exterior wall vertical bracing. The angle shown is resisting 53 kips seismic. I have sketched two possible bracing senarios:
W.P. at column flange - much easier detail, however creates a torsional/twist load in my column.
W.P at column centroid of column - much uglier detail.

Does someone have a better detail with W.P. at column centroid?

Thanks,
Jeff

 

[KootK]

Make your brace connection to the horizontal beam in your sketch rather than the vertical one. This way, the load will be delivered in such a way to avoid torsion in the column.

You would need to ensure that the beam taking the eccentric the brace load can handle the weak axis shear & bending. Probably some arrangement of stiffeners and plates to drag the load into the beam flanges.

Also be careful with your beam-column connections. The double angle connections shown might not be up to the task.

 

[hokie66]

Looks to me like you can provide a vertical cleat into the beam to column web intersection rather than the horizontal cleat you have shown. Much more compact. Agree with KK about the beam to column connections. And the column may need some horizontal stiffeners.

 

[weab]

Agree with KK. Option 2 is better, but...

I don't care for either one. I'm not sure that your gusset plate can handle the moment. If it can, are you connecting to the beam web or the flange? If the web, then you need some web stiffening. If all that works, then I don't think the clip angles will transmit moment. Likely, the moment component goes into the beam as a concentrated moment that is taken out as a couple at the beam ends.

Are you trying to optimize? save installation labor? If not, I would combine both of your details and attach to both beams. Make the line of action through the column center and the load gets taken out in shear through both beams (53 kips x cos(angle)).

Maybe I'm not visualizing well tonight, but I can't see how to do a vertical cleat like hokie says without interfering with clip angles and bolt access.

Hope this helps.

 

[hokie66]

I should have explained better. I would get rid of the double angles, which we never use in Australia. Either use vertical cleats for both the beam and brace, or use an end plate for the beam with the bracing cleat welded in the end plate/beam web juncture.

 

[paddingtongreen]

I'm old fashioned, I would use the one going to the column center, but my gusset would be "L" shaped to connect with both beams, then I consider that only shear is transferred to each beam. This is a reasonable assumption because the beams are much stiffer axially than they are in out-of-plane flexure. It sounds like more material but you don't have to jump through hoops to get that out-of-plane force and bending moment through the one beam end to the column.

Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[bootlegend]

I do the same thing paddingtongreen does. Like he said, the brace force transfers as just axial load in each beam.

I don't know much about statistics, but I do know that if something has a 50-50 chance of going wrong, 9 times out of 10 it will.

 

[jchi]

Thanks Paddingtongreen, I agree, I like the L-shaped clip the best.... Was getting late yesterday and I was stuck!

Thanks for all the replies!
Jeff

 

[Stillerz]

Yep, use a "boomerang" gusset.

 

[KootK]

As diaphragm bracing for seismic loads, this connection has to take compression as well as tension, right?

Aslo, hokie: why are double angle connections not used in Australia? Is it just the standard practice or is there an objection to the connection perfomance?

 

[jchi]

X-bracing so I am only looking at the tension loading.

 

[hokie66]

KK,

Good question, and I don't really know the answer. Double angles aren't prohibited, just rarely used. Probably just the way the fabrication industry here evolved. The connections we use don't have the flexibility of double angles, but then we don't have much in the way of seismic concerns.

 

[KootK]

So what do you guys use hokie?

 

[hokie66]

End plates or web cleats.

 

[Stillerz]

Hokie-

Are "Web Cleats" similar to "shear tabs"?

 

[hokie66]

Had to look up "shear tabs", but yes, they are the same.

 

[slickdeals]

See example of wrap-around gussets in this paper

http://www.cives.com/Assets/PDF/Con...ation in the Quest for Economy and Safety.pdf

I did not know they were called "boomerang gussets". Interesting!