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Footing of corner column at property line

Footing of corner column at property line

Footing of corner column at property line

(OP)
My corner column sits at property line, in both X and Y directions. The interior column in Y dir is far way and its load is negligible. So I cannot use it to do combine or strap footing with my corner column. The adjacent column in X dir is also along property line and its own footing is strap with its own Y dir interior column footing. So basically my corner column cannot tie into footings in X and Y dir.

Therefore I designed a spread square footing with my corner column sits at the corner of the footing by including eccentricity in both direction. That ends up a 12'x12' size for column loads at 50 kips and soil net bearing at 2500 psf. The column has beams in both direction to tie into adjacent columns. I wonder if that works. Please let me know.

I also wonder if "L" shape footing work with my corner column. But I don't know how to calc "L" footing. Please let me know.

Thanks a lot!

RE: Footing of corner column at property line

You could place a cantilevered grade beam at 45 degrees from the corner.  The grade beam would cantilever off a buried footing located just inside the corner.

The grade beam would then extend into the building and have a buried, heavy pad as counterweight.

This is an option - it may be more expensive (more formwork, rebar, etc) than just a large corner pad though.

RE: Footing of corner column at property line

I like JAE's option.

How did you get an eccentrically loaded footing to work, with the column on the corner?

DaveAtkins

RE: Footing of corner column at property line

(OP)
DaveAtkins,

I put a large eccentricity, say 70", in both directions. That is why it needs 12'x12' size footing. The footing absolutely has partial bearing. As for overturning, I used footing weight , soil weight and slab-on-grade weight over footing to counteract. If you think this is not correct, please let me know. I want to know why.

For now I will use JAE's suggestion for a safer design. I actually used this method for footings of edge columns at property line along X dir.

Thank you two very much!

RE: Footing of corner column at property line

What you did sounds correct.  I only commented because in my experience it is difficult to put a column load on the corner or edge of a footing while keeping the bearing pressure manageable.

DaveAtkins

RE: Footing of corner column at property line

How about a pier?

Never, but never question engineer's judgement

RE: Footing of corner column at property line

I'd agree with COEngineer that a vertical support element  seems like a preferable solution.  Since your loads seem relatively low maybe something like helical piers would be a cost effective alternative solution.  You might even find it to be cheaper and better to also use them instead of strap beams for the other footings you mentioned.

RE: Footing of corner column at property line

How about lowering the corner footing, deepen the x and y grade beams and put two smaller footings midway between the other x and y property line footings.  The deeper grade beams with top rebar will then will cantilever out to the corner column.  You will still need a small corner column footing, but there will be no eccentricity on the footing since it is taken out by the two cantilever grade beams.

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