Anchor Rod Setting Plate

[jranderson]

We have just recently had the anchor bolt fabricator providing 1/4" setting plates that are welded to the anchor rods to assist the installer in setting the rods. Our current project, the installer placed the setting plate flush against the concrete footing leaving no void between the two. This to me seems to be an issue as th top of the footing is rarely flush and smooth. This could create a void between the setting plate and footing and inturn could create a void below the structural column base plate. My question is whether anyone has a good reference on how these rod and plate combinations are to be installed? I feel the setting plate should be left up from the footing to allow the grout to be installed under the setting plate but could be wrong. Any feedback would be appreciated.

 

[dik]

My involvement with anchor rod setting plates is that they are loose and the anchor rods are cast into the concrete with the top of plate established at the U/S of base plate. The cover plate is grouted and removed to insure that there is grout continuous under the setting plate (and, therefore the base plate). The setting plate is put in place on top of the grout and the column installed over.

Dik

 

[ARKeng]

jranderson - we always detail at least 1" (usually it's more like 1.5" to 2") of grout between the base plate and the top of concrete.

It's not just a bearing issue - usually the top surface of the footing is reasonably smooth. But if there's no grout, I don't see you have any adjustment for the steel - the concrete better be PERFECTLY level in order for the column to turn out plumb... And if it's not, how do you fix it except by adjusting the angle that the column attaches to the base plate? Are they going to measure every one of those with a precision necessary to adjust prior to column fabrication? More than likely no, and even if they were, they'd drive the steel fabricator insane. It may depend greatly on how tall your columns are - they're only 10' tall, they might not have any trouble meeting tolerances (even though it's a crappy detail). But if you've got a 3-story, 55' tall column - good luck getting it plumb.

As far as references, I just looked up page 14-7 of my AISC 13th edition. If you've got a different edition, just look up "grouting and leveling" in the index.

Final thing is with reference to welding the setting plate to the anchor rods. In general, I HATE welding to any kind of bolt. If you're a grade 36, you might be able to get away with it, but in general I discourage any kind of "bolt / threaded rod" welding because it promotes bad habits. High strength bolts shouldn't even be tack welded. The other thing with this is "welding" them also ruins the leveling adjust-ability just like placing it tight against the concrete. I don't know why you'd want to anyway - a nut on each side of the setting plate is more than enough to keep it from moving and is less money/time/effort than a weld.

 

[LarryAndrews314]

If you have a pretty big anchor bolts I would recommend two setting plates to prevent the bolts from racking. Racking is a very common issue with CIP anchors bolts. One near the bottom of the bolts and one a couple inches above TOC. The top one sandwiched with nuts and the bottom would require some type of weld. This would be a tac weld to the shank so I'd think it would avoid the bad habits ARKeng is talking about. After pouring the top plate can be unbolted, the column flown in and plumbed with the set of bolts beneath it. I'd detail at least a couple inches of grout here or the lower set of nuts will be cast into the concrete. I'm gonna go against what dik said and say never grout before plumbing the column. Plumbing with some bolts is much more practical that trying to get an incredibly precise grout pad. Last thing is make sure the setting plates are as minimal as possible. Large, obtrusive plates prevent proper finishing or could cause the bolts to float.

 

[dik]

I'm not sure how they establish a level setting plate, I agree that it's easier to plumb a longer element. They may use a precision level, like a machinists similar to that used for large equipment bases, such as presses, etc. I've only seen the end result, and that was with large columns.

The only purpose I've seen with setting plates is to insure that there is grout continuously under the base plate, and not to secure the anchor rods.

Dik