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Concrete Post Installed Wall Plates - Standoff, Leveling Nuts, Grout Pads Etc.

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JoelTXCive

Civil/Environmental
Jul 24, 2016
919
US
My office does a lot of work where we go into existing WWTP or storm water pump stations and remodel them; or we build new items within an existing plant.

We often come across the issue of attaching new pipe supports, ladders, or work platforms to an existing concrete wall. While structurally sound, the concrete walls we are attaching to are often far from a perfect surface. It might be a bowed wall, out of level, out of plumb, etc. etc.

This always makes attaching things and designing wall anchorages a challenge.

Does anyone know a good design resource for post installed concrete anchorages for these types of miscellaneous items?

I have a several questions but the main ones are:

1) Can wall plates use levelling nuts or grouted pads to correct for imperfect surfaces?

2) Bolt holes? Standard bolt holes only, Short slot transverse to the load, or can larger baseplate holes be used with plate washers?

I have searched all over for literature on this subject but not found any. The best I have come up with is Daniel Horn’s Monopole Base design guide and the AISC Baseplate Design guide.

These are excellent resources, but the loading is different. (See attached image)

I appreciate any comments or direction towards a book or journal article.

Thank you in advance….
Wall_Plate_Question_dhpdq3.jpg
 
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Threaded rods with adhesive anchors (e.g. Hilti HIT RE 500) and leveling nuts should be a good option. There are a few things to watch with them, though:

1) In our experience, proper preparation of the hole and the material has been an issue. The hole must be thoroughly cleaned and the 2 parts of the material mixed well, to get a good bond to the concrete and for the material to harden.

2) Be sure to spec a material suitable for the orientation of the hole. Some systems/materials are only suited for vertical applications (holes in a slab or floor), while others are for horizontal (walls) and/or overhead (ceilings) applications.

I don't know what is available in the way of grouts suitable for use on a wall. The ones we use for grout pads under post base plates would likely slump or sag in a vertical application.
 
I have dealt with wavy concrete walls by using horseshoe shims under the plate at each anchor, as needed. I don't recall ever using grout under a wall plate. Haven't tried stand-off wall plates either, but I don't see why it wouldn't work, though your plate would likely be thicker. I tend to use slotted holes in the beam-to-plate connection to achieve construction tolerance, rather than making the plate-to-wall connection adjustable.

I usually spec hole diameter = bolt diameter + 1/8" for all steel-to-concrete connections. There will inevitably be some slippage of the plate and/or deformation of the bolts required to mobilize the resistance of all anchors in shear. The degree of slippage depends on hole size and anchor alignment. For a given connection, I decide whether a nominal slippage of 1/8" would be acceptable or not. If not, I spec welded plate washers with a hole size 1/16" greater than the anchor size to limit the movement required for full anchor engagement.
 
Also, I don't see any issues with slotted holes in the wall plate perpendicular to the load. The same principles should apply. Hopefully with a post-installed anchor, they would installed with enough precision that slotted holes wouldn't be necessary. But I can't see any downsides besides added cost.
 
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