Bending on Anchor Rods

[SperlingPE]

I am doing an addition to a freezer facility. As part of providing a continuous thermal barrier. The insulation sub-contractor wants to put a 5" deep high density block under the column base plates. Where I have x-braces, this would put the bolts in bending.

Does anyone have any good ideas on how to transfer this lateral load (from wind) into the foundation without putting the bolts into bending?

 

[COEngineeer]

Dont put block under the base plate and insulate the whole column? You do your structural element, let them figure out how to insulate it.

Never, but never question engineer's judgement

 

[SperlingPE]

Thanks COEngineer
This is not an option.
There are several problems that come up that can be handled that way.
This situation I am working as a problem solver with a team and not on an island providing a service.

 

[WillisV]

Field install L8x8 angles to each side of the baseplate in line with the x-bracing. Weld top leg to baseplate. Fasten bottom leg to concrete with post-installed anchors (like screw anchors - Titen HDs etc). Assume angles take all shear. Assume anchor bolts take all uplift.

 

[rday]

Could you move the baseplate down and place the 5" of insulation above it around the column?

Is there a slab?

Even with the 5" below the baseplate, you still get conductivity through the bolts, right?

How big are the bolts?

Maybe the previous idea would provide similar thermal break?

With 5" offset, I can't see any simple way to avoid designing for bolt bending. You could put plate stock between them on egde, but then you may as well just extend the column down.

Any idea how it was done on the existing facility?

Hope my comments aren't too scattered, just thinking "out loud".

 

[SperlingPE]

Existing facility was built 20+ years ago and this was not done. Insualtion sub-contractor says that the structural engineer that he has worked a lot with doesn't give this a second thought.

I am goin gto look at putting the column on the concrete pier.

Any steel that is in the slab or in contact with the floor insulation has to be insulated.

 

[kslee1000]

Either bring the column down to pier, or raise pier to slightly higher than the floor, then insulate slab-column/slab-pier interface.

 

[MikeDB]

Have you considered larger anchor bolts with a nut above and below the base plate? You will likely need a thicker base plate to handle the bending in it as well.

Utility structures and Highway structures are often built with the distance from the top of concrete to the bottom of the base plate equal to two to three bolt diameters.

 

[IFRs]

Can you add a shear key to the column and a cavity in the concrete under the insulation? Then design the base plate and shear key for bending, keeping the anchor bolts for tension and compression. The shear key could have a small cross section in contact with the concrete - still a thermal contuit but perhaps a small enough one? If the shear could be in two directions, use a cross shaped key. Regarding the other guy who would do it without questions, he/she was dead wrong and should be reported to the PE board (my opinion only). Unless of course he/she can back it up with a technically defensible argument. Don't fall for that garbage!!!

 

[csd72]

Arent the bolts going to be a cold bridge anyway?

If they are willing to accept these then maybe they would be willing to accept a tube section welded to the underside of the base plate and embedded into a grouted hole. This takes out shear only.

 

[civilperson]

Design the bolts for bending stress and do not forget to heat the subgrade! (Insulation only delays freezing.)