Footing of corner column at property line 1

[aquacata]

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!

 

[JAE]

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.

 

[DaveAtkins]

I like JAE's option.

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

DaveAtkins

 

[aquacata]

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!

 

[DaveAtkins]

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

 

[COEngineeer]

How about a pier?

Never, but never question engineer's judgement

 

[motorbiketocrank]

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.

 

[mfrad]

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.