Foundation bearing

[Navid.Nik]

In a project, they made a mistake in installing a mezzanine and the whole structure is shifted. Since the columns are not matching the location of the foundation pads any more, the foundation does not fulfil. Could someone please advise a solution for it?

The foundation is built, and the mezzanine has SHS columns which are connected via post installed anchors to the foundation.

Thank you.

 

[jayrod12]

There isn't going to be a pretty solution. If you've run the numbers on the as-constructed condition, and the bearing capacity of that integral pad is exceeding allowable, then you have to replace it.

Or dismantle and re-construct the mezzanine with the column in the appropriate place.

So really, two options.
1) Remove the pad and replace to suit the actual column location
2) Re-frame the mezzanine so the column aligns with the pad

I guess there's a potential third option, but your mileage may vary on it, and that is ground improvement via injection may allow for an increase in allowable bearing pressure. The tough part with that is finding a Geotech that is willing to quantify it.

 

[SlideRuleEra]

Remove the part of the floor shown in red and construct an independent spread footing of suitable size for the column:

http://www.SlideRuleEra.net

 

[wrxsti]

if the bolts can still be installed in that location you can check for possible raft action with the slab
based on your drawing

but that is highly dependent on your soil properties

see detail below

Slideruleera seems like safest solution if you can still get existing bars to tie in with the new pad

 

[SlideRuleEra]

wrxsti - My proposal is for an independent footing - no rebar or other connection to the existing slab.

With good geotech information, should be possible for expected settlement of the proposed independent footing to match expected settlement of the existing slab. If there is differential settlement, IMHO (based on experience), better to let it happen than to have the footing tied to the slab... no reasonable amount of footing-to-slab rebar is going to stop the settlement without making a "mess" of the slab, the footing, or both. Since the loaded column footing will usually tend to settle more than the slab, any mismatch in elevation can be handled later with a thin topping on the footing.

http://www.SlideRuleEra.net