retrofit steel post - installation issues

[SLTA]

I have been asked to design the replacement of existing CMU piers with steel posts, to hold up an existing LVL beam. We're pouring new footings and a slab to finish the space. The detail I can't work out is how do I get the column in, tight against both the new concrete footing and existing beam above. I am using a U-shape bracket screwed to the top plate of the steel post and to the LVLs at the top, and at the bottom I was thinking of using cast-in anchor bolts that use nuts to level and get the post tight to the underside of the beam, but then I realized I can't get the column on over the extended anchor bolts because the beam above would be in the way. Then, I thought of using retrofit epoxy bolts into the concrete, but how do I get the post up tight to the beam? I guess I'm not trusting that the final length of the post assembly will be exactly what's needed based on field measurements, given that this is a small renovation job on a house.

This is done so often - there has to be a way to do it, other than using jack posts. I'd love to see or hear about typical details and construction processes.

thanks!

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[JAE]

We would use screw-jack columns. Otherwise, you need to require the contractor to slightly jack up the beam some distance (small distance) and then insert the new column and install shims tight to the beam. Then let the jacking off to allow the beam to settle into place. This ensures a tight connection with no net loss of vertical elevation of the supported floor.

The trick is to get the initial temporary jacking force right. Possibly 1/8" at the very most. Just enough to lift the dead load off the current masonry suppor

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[Ron]

SLTA....one of those situations where you have to get involved in means and methods. You can't leave the limits up to the contractor and JAE has given reasonable limits in his technique. Jacking to remove existing dead load is tricky, but can be done if careful as JAE notes. I agree with this method. Another is to use a floating head on the column that can be adjusted incrementally to give tight fit, assuming you will have trim or enclosure that would hide the bolts necessary to accomplish this. Can also be field welded, but probably wouldn't allow that inside a home!

 

[JAE]

Ron - I'm not sure but is your "floating head" column the same as my term: Screw jack column? It is a simple pipe column manufactured with a vertical threaded portion at the top, just below the base plate, so that the final column length can be adjusted.

Here's a link to one:

http://www.hardwarestore.com/jack-post-685011.aspx

Usually they offer 15k to 25k capacity.

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[SLTA]

Thanks, folks. The jack post got me thinking - I found a retrofit post where you pour the slab over the screw part, which locks the height in place. Perfect.

cheers!

Please remember: we're not all guys!

 

[Ron]

JAE....similar, just using offset bolt holes and through-bolts to take the load.

Another trick is to use the screw jack and put a tack weld on the screw to make sure it doesn't move after final adjustment.