Shoring a column 2

[JStructsteel]

Got a situation where a column needs to be shored to replace a footing. Plan was some channels each side of flange, all welded up as needed. What else do I need to look out for? Obviously check the channels for bending, bearing, etc. Any issues with column? Stiffeners needed?

 

[JStructsteel]

PE inc its hard to see, but I have some plates top and bottom welded to the channels.

 

[SlideRuleEra]

Ok, here is my understanding... it does not make total sense to me, but my best interpretation:

Blue - Is the bottom of the cribbing below grade?

Orange - Some soil (wider than the perimeter of the footing) will be disturbed during demolition... how much is an educated guess.

Red - If an eccentric load were applied to the cribbing, note that contact pressure between cribbing and soil is highest at the worst possible place... closest to the excavation. Avoid eccentric loading, as much as possible.

Green - Nine inches is a ridiculously tight clearance. The excavation is shallow, but the risk of heavy equipment accidentally impacting heavily loaded, weak (Y-axis) beams is high. I would want that distance to be at least 3' instead of 9"... of course there are consequences:

The selected beams that passed for 10' span, likely fail for 14.5' span. Revisit beam size and bracing, do what it takes to increase Y-axis strength.

There is probably more, but that is what I see with my assumptions... comments?

 

[TLHS]

Unless there's huge space restraints I'd assume at least 6" of over-excavation below the footing (potentially 12") and a handful of inches to the side, and then draw a load influence area from the cribbing to see if they interact.

The extra beam length to buy a couple of feet is way cheaper than the stress involved if you need to try to qualify it after the fact for dealing with field requirements.

I've basically never ended up thanking myself for being aggressive on shoring work. I often tell myself initially that what I've got on paper looks excessive and then talk myself into bringing things down. In the field, though, it rarely actually looks excessive.

My question is whether there's any reason to be concerned about lateral restraint on this column. Does what you've got provide enough restraint into the page for whatever buckling conditions may be expected? The normal assumption is that the base is stiffly restrained in the lateral directions. Here you've got reduced friction and weak axis bending in the channels. It's likely okay, but it depends on the geometry of everything. Do you want to run a tie to another column into the page?

 

[JStructsteel]

Update: Contractor completed the new footing. He reported they had no issues with movement, sliding soil, etc. They leveled out the soil to be at the same elevation as the footing. They were able to jack up the existing column to where it was previously.
Thanks for your help