New footing to be installed over existing footing
New footing to be installed over existing footing
(OP)
Please see attached. We are looking at installing a new steel gravity column and footing in an existing building. The issue we have is that the centerline of the column is directly over the edge of the existing footing. We are looking at overpouring the new foundation over the existing but can not bear the new footing on the existing because of the increase eccentricity created. My question is whether anyone could provide suggestions in how to install the new footing. Possibly a pile through the existing footing for bearing? Or direct me to articles discussing this installation.






RE: New footing to be installed over existing footing
DaveAtkins
RE: New footing to be installed over existing footing
You'd need to make sure bending between the columns is ok - I'd check as plain concrete first and go from there.
RE: New footing to be installed over existing footing
I would also pour the new footing up to the top of the existing footing.
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask
RE: New footing to be installed over existing footing
if I am not mis-interpreting the sketch, I think the new footing will be just at the edge of the old footing and above the old footing?
If this is so, my thoughts will be to excavate the new foundation to the base level of the old footing (with 45deg sloping out), and fill with compacted rock gravel or pour mass concrete if the budget can afford this, to bring the bottom of foundation of the new footing to the top of the existing footing.
as per the pressure exerted on the existing footing; i reckon these will be greatly reduced at the corners. it depends however on how nuch load is being transferred to the foundation level.
RE: New footing to be installed over existing footing
The area of the new footing should provide the area required for the new load outside the existing footing and should be centered under the new column.
BA
RE: New footing to be installed over existing footing
too $$$ probably
RE: New footing to be installed over existing footing
RE: New footing to be installed over existing footing
RE: New footing to be installed over existing footing
RE: New footing to be installed over existing footing
RE: New footing to be installed over existing footing
RE: New footing to be installed over existing footing
You could put styrofoam on top of the existing footing to prevent it from being loaded by the new footing, and design the "green" footing to span across the existing footing.
DaveAtkins
RE: New footing to be installed over existing footing
Yes, you could do that. Somehow, the additional pressure from the new footing didn't seem like much of a problem to me. I even wondered about mechanically fastening the two footings together, forcing them to act as a unit.
BA
RE: New footing to be installed over existing footing
RE: New footing to be installed over existing footing
Kieran
RE: New footing to be installed over existing footing
Those anchors will be designed for any additional loading imposed by new column on the existing footing. Hence, you will be able to pour footing right next to existing one. You will certainly be specifying bonding agent on the face of existing footing as well as the reinforcement dowels epoxied into the existing one for continuity of the reinforcement of new one.