Transferring shear from column base to slab

[akamike]

I have a huge shear load (200k) at a TS6x6 braced frame column base that needs to transfer to the foundation. It's too much to take through anchor bolts into a spread footing. I'd like to transfer it to the slab on grade -- maybe thicken up the slab in this area. Any tips how to transfer the load? Maybe weld a channel perpendicular to the column just under top of slab?
Thanks.

 

[swearingen]

AISC's Steel Design Guide Series #1 "Column Base Plates" deals with this. One of the methods listed is to use shear lugs, which work on the same principal as your channel.

If you can find the Design Guide #1, you'll be in good shape - they give worked examples. If you are an AISC member, it is free for download from their website.

 

[Ginger]

If the foundation slab has not been cast yet, how about casting pockets in the slab for your steelwork columns to be grouted into at a later date. Beware that this may change the fixity of the base joint from a pinned to a fixed connection.

 

[DaveAtkins]

Where does this huge load go to once it is in the slab?

DaveAtkins

 

[jike]

Is this from a gravity loaded chevron brace? If so, can a portion of this large load be counteracted by the equal and opposite force from the other brace? This can be accompolished with a steel tension member from the base of one column to base of the other column.

Then only the shear from wind or seismic has to be transferred.

 

[akamike]

Thanks, everybody! Dave, I'm hoping to transfer the load to some large footings at adjacent gridlines where it can be taken out by soil/conc friction and passive pressure against the footing. Unfortunately, jike, it's all seismic. (The brace was designed by others and I'm designing the foundation.)

 

[shepherd]

I've took the approach of dropping the column base below the slab and spanning a steel beam between the columns of the braced frame. The beam will be encased into a shear wall with shear studs to transfer the load into the wall.You'll have a shear wall between your concrete piers below grade. You could tie these footings to adjacent footings for further resistance.

 

[jloo73]

I would take a similar approach to shepherd and swearingen.

I think you would need some type of shear lug or key and transfer load directly to the footing in bearing. I would tie the two footings of the braced frame with a concrete grade beam. Provide dowels in the grade beam to transfer load to the slab on grade and then design your slab on grade to act as a diaphragm as you intended on doing.