Transferring large lateral forces at base of braced frame 2

[abusementpark]

What mechanism do you generally rely on to transfer large lateral forces at the base a braced frame to the foundation?

Anchor bolts in shear? Shear lug? Bearing directly from column into slab concrete? Some other mechanism?

 

[neffers]

I have been using shear lugs.

Neffers

 

[csd72]

We used to use reinforcing bars through a hole in the web to transfer it into the ground slab. You have to do a pour strip.

Using anchor bolts for significant shear is normally not advised.

 

[ToadJones]

Typically a shear lug, in my neck of the woods

 

[Lion06]

I provide an embed plate for the gusset to get welded to. The embed plate has rebar welded to it (designed for shear friction) to get out of the App. D requirements. The rebar designed for shear friction allows for a more manageable size and qty of bars when compared to using headed studs with App. D implications.

I've used this on a lot of jobs and it seems to work well. It's just like any other embed plate that the concrete guys cast into the structure. We've never had any complaints................... yet.

 

[StructSEZ]

I tend to take a U-bar from reo and thread the two ends.
They then extrude out the top, whilst the 'flat' of the u-bar is cast in.

 

[sandman21]

Weld rebars to the top of the base plate then develop them into the grade beam using U-bars.

 

[abusementpark]

How do you specify and design the weld of a rebar to a structural steel plate? Is it just a full-pen weld and you assume the strength of the weld doesn't govern?

 

[slickdeals]

See PCI Manual 6th Edition Pages 6-85 and 6-86

 

[Lion06]

Slick has it. There is a table there that gives you the required fillet weld to develop different size bars.

Also, make sure you use low-hydrogen electrodes and A706 rebar. You'll get more reasonably sized fillet welds with E90 electrodes, too.

 

[abusementpark]

Lion06,

Do you hook the bottom end of the rebars or just provide full development length?

Also, you weld the gusset plate directly to the embed plate? There is no column base plate? What about uplift?

 

[Lion06]

Abusement-

The column comes out with a baseplate like usual. There are anchor rods for the column for uplift. The embed is offset slightly from the column (just a detailing exercise based on column and baseplate size.

I hook the bars if I need to. For example, if I am trying to develop #8's in a 4' deep grade beam. Usually I don't have to hook them, though. I try not to and only hook them if necessary.

We show the gusset welded directly to the embed, sometime the fabricator wants to hold it up just a little. In that case, we field weld plates on either side of the gusset and to the embed. Shear only at the embed, shear and moment at the gusset - for designing those additional welds.