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Old 08-31-2022, 11:41 AM
threepiece threepiece is offline
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Default Suggestions for Attaching Steel Steel Column on Concrete

Fellows, I already have an 8”block wall six courses/4feet high filled with vertical re-bar and concrete. I want to place a load bearing column on it. The column I intend to use will be made from 6” WF beam with a 3/4” or 1” thick steel plate welded to the bottom.

I plan to make the bottom plate a full 8” wide and 16” long to spread the load and avoid stress points/risers.

I am looking here for a suitable “cushion” To place between the bottom plates and concrete.

Some type of wood or engineered wood product is my choice at this point. Does anyone here recommend a particular one or perhaps something completely different like urethane?
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  #2  
Old 08-31-2022, 12:22 PM
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I don't know if this is code or not.

1. Treated 2x10, cut down to match your steel plate. This is likely what I would do.

2. Grout between the steel and block.

3. Bolt it down and be done.

I am assuming that all the load is vertical and no shear stress on the connection.
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Old 08-31-2022, 12:31 PM
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What is the column doing/why do you feel the need for a cushion?

My initial thought would be a bed of Tec7, just enough to fill the irregularities in the block. It is sticky stuff in a tube that I've no idea of its chemistry and I assume is not available stateside anyway.

Something sticky that won't dry hard. Steel and concrete are very long life materials, I wouldn't like to put wood between them personally
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Old 08-31-2022, 12:57 PM
threepiece threepiece is offline
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Quote:
Originally Posted by Shade Tree Welder View Post
I don't know if this is code or not.

1. Treated 2x10, cut down to match your steel plate. This is likely what I would do.

2. Grout between the steel and block.

3. Bolt it down and be done.

I am assuming that all the load is vertical and no shear stress on the connection.
Code? What’s that?

With the exception of grout, this is exactly what I intend to do unless someone has a better idea. Grout, nice touch!
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  #5  
Old 08-31-2022, 01:07 PM
threepiece threepiece is offline
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Quote:
Originally Posted by JohnBoy View Post
What is the column doing/why do you feel the need for a cushion?
Because I am not confident in my ability to lap the steel plate and concrete surface correctly.

Seriously, because the concrete surface (and steel plate after welding) is irregular I don’t expect the entire surface of the steel plate to make contact. This means there will be areas of the interface that will be under higher stress than others. I believe these stress points could initiate cracking of the concrete. I want to apply an even force over the entire surface.
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  #6  
Old 08-31-2022, 01:12 PM
threepiece threepiece is offline
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Quote:
Originally Posted by Shade Tree Welder View Post
I don't know if this is code or not.

1. Treated 2x10, cut down to match your steel plate. This is likely what I would do.

I am assuming that all the load is vertical and no shear stress on the connection.
I am actually planning to trim the board several inches longer lengthwise to help feather-out the load at the outer edges.
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  #7  
Old 08-31-2022, 03:52 PM
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We use a piece of 5/8” plywood when jacking the mining shovels, between steel and steel. Four pieces about 2’ x 2’ hold up a couple million pounds.


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  #8  
Old 08-31-2022, 04:06 PM
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Back in my construction days of steel post and beams onto concrete footing/ block walls, etc. we never used wood as a cushion.

I understand your situation, and we ran into that a lot. Just several high spots touching the post pad. Probably the best way if your blocks are poured solid, drill and epoxy threaded rod and leave a 1-1/2” to 2” gap. This will allow you to plumb the post exactly too. Then fill the gap with non shrink grout.

The grout I used to use, you wanted to mix it with as little water as possible. And as it cures, it actually expands slightly, so it will take the load bearing stress.

I think there is a minimum thickness for this too. I think in engineered prints, they called out a minimum of 1” grout.

If you put wood in there, and then if it ever gets wet, it could rot away, causing more problems.


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  #9  
Old 08-31-2022, 06:03 PM
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Quote:
Originally Posted by threepiece View Post
Because I am not confident in my ability to lap the steel plate and concrete surface correctly.

Seriously, because the concrete surface (and steel plate after welding) is irregular I don’t expect the entire surface of the steel plate to make contact. This means there will be areas of the interface that will be under higher stress than others. I believe these stress points could initiate cracking of the concrete. I want to apply an even force over the entire surface.
Gotcha.

In that case a non shrinking grout like toprecycler says.

I hate the look of it with the post floating and then the grout filling it but it's how whole buildings are bolted down.

It always looks weak, but it's actually strong
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Old 08-31-2022, 08:07 PM
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Quote:
Originally Posted by toprecycler View Post
...Probably the best way if your blocks are poured solid, drill and epoxy threaded rod and leave a 1-1/2” to 2” gap. This will allow you to plumb the post exactly too. Then fill the gap with non shrink grout.

The grout I used to use, you wanted to mix it with as little water as possible. And as it cures, it actually expands slightly, so it will take the load bearing stress.

I think there is a minimum thickness for this too. I think in engineered prints, they called out a minimum of 1” grout...
Pretty much exactly how I would do it--I've put in quite a few columns that way. Make your post and plate short enough that you can have a nut above and below the plate; that way you can jack it around to level and true it. Then fill the gap with a relatively dry mix of expanding grout. I would NOT use wood because of the possibility of rot sometime in the future...
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