Benefit to welding washer to baseplate? 1

[StructureMan44]

When anchoring a column baseplate to existing concrete, is there any benefit to welding the edges of a square washer to the baseplate?

Specifics:
1-1/2"Ø Anchor through 2-5/16"Ø holes in 1" baseplate
Square washer is 1/2"x3.5"x3.5" with a 1-9/16"Ø hole

While reviewing the drawing I haven't thought of a benefit to welding the washer to the baseplate.

 

[WillisV]

Shear transfer.

 

[structSU10]

it is to transfer shear forces to the anchors. The holes in the base plate are huge, so the bolts must bear against the standard holes in the washer, and thus the washer need to be welded to grab the force from the base plate.

 

[StructureMan44]

Makes sense, thank you

 

[Tmoose]

looks like in the worst case that square plate will cover the 2-5/16" hole by less than 3/16"

 

[racookpe1978]

Yes, the square plate needs to be larger - though it has the smallest reasonable hole.
What size fillet weld for the 1/2 thick plate to the baseplate? What is the shear force expected, a 1/2 inch fillet seems much too heavy to be economical.

 

[thaidavid40]

Agree with @Tmoose: the plate washer ought to be more like 4.5" square for this application.
Dave

Thaidavid

 

[wannabeSE]

The 2-5/16" hole with a 1/2" x 3-1/2" washer for a 1-1/2" anchor rod is the same as what is listed in AISC's Steel Construction Manual, 14th edition, Table 14-2.

 

[bearjew]

What's the reason for having the larger holes in the first place? Why not use a 1-9/16"Ø hole in the baseplate itself and skip the washer? I'm guessing for easier field setting of the anchors...

 

[TehMightyEngineer]

What's the reason for having the larger holes in the first place? Why not use a 1-9/16"Ø hole in the baseplate itself and skip the washer? I'm guessing for easier field setting of the anchors...

On a small structure or when using post-installed anchors this would entirely be possible. However, on larger projects (multi-story buildings, etc.) the anchors are cast-in and neither the anchor bolt tolerances nor the structural steel tolerances will allow for standard bolt hole tolerances or even oversized bolt hole tolerances. Often you'll need tolerances beyond the oversized bolt hole for your anchor bolts to fit in the base plate.

Plus, it's almost always cheaper to weld washers than to fight with slightly misplaced anchor bolts or re-fabricate steel.

Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries

http://www.americanconcrete.com