I'm sure this has been discussed before but I can't find the magic "keywords" to match my question...so please bear with me.
1. An existing pre-engineered steel building supported by reinforced concrete pier/spread column footings.
2. New pre-engineered steel building addition to be constructed immediately adjacent to existing.
3. Addition columns set in line with existing columns to maximize clear (aisle) space when existing wall is removed.
4. Addition columns are set within 12" of existing building wall.
None of this is a reinvention of the wheel, I know. With the "givens", it's obvious that the new column's pier and spread footing MUST share space with the existing's. Let's say that the existing column has an 8'-0" square spread footing centered beneath it...this leaves approximately a 3'x8' pad of concrete, ( 4' below grade...welcome to northeastern Pennsylvania) extending outside of the foundation wall.
The new footing should bear at the same elevation as the existing, so as not to induce lateral stresses, etc., but how can these two separate entities share this space. I've seen designs where the new column pier simply bears on the existing footing and "extra concrete and rebar are scabbed on" to increase the bearing area. The bar is sometimes drilled into the existing footing, but I don't know many contractors who would not tear my head off when I spec a 24" deep drilling to generate the required development length.
In the past I've seen a concrete bridge beam placed under the new column, which piers down to two footings on either side of the existing, but offset footings can get so big since they're forced up against the existing wall...let alone compensating for the pre-engineered horizontal shears and induced moments that come with them.
Has anyone "thought outside of the box" successfully for this seemingly common, yet head-scratching, problem?