combined foortings max spacing between columns

[malikasal]

Hey:

Is there a provision limiting the max spacing between 2 columns to be supported by a 1 combined footing??



ôIf you don't build your dream someone will hire you to help build theirs.ö

Tony A. Gaskins Jr.

 

[Teguci]

I'd think shear, moment and money would be the limiting provisions. What are you thinking about doing?

 

[KootK]

Some codes will have shear span limits beyond which a footing ought not be considered rigid. Other than that, it's economics as Teguci has suggested.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[BSVBD]

malikasal - to (not necessarily) answer your question, I'm not aware of any provision or limitation.

When you say "provision", i think "code". Although there are a reasonable share of "reasonable" code limitations, when it comes to structure, i perceive that most code reviewers rely on us to prove that our calculations are sufficient.

To support Teguci, structure would typically govern.

I've had numerous and various situations that warrant long rectangular column footings, where square is not acceptable, that, when intersecting with adjacent column footings, i was forced to "combine" the two into one. On some occasions, after i've created a combined footing that i was questioning myself about, i would then recalc each as a separate footing to see if they would stand alone if NOT combined. (I hope i'm not muddying the waters - let me know if you want clarification)

In combined footing design, I don't recall ever considering a limitation distance between columns. Again, structure would govern.

On a few occasions, when challenged, with success, I've reasoned with code reviewers that, (in reasonable cases) some limitations of code should be considered empirical if i can prove structural integrity.

 

[malikasal]

Thank you guys,

Kootk can you please elaborate in the shear span limits issue which will affect the rigidity, because this is the warning i am having when using ram foundation.



ôIf you don't build your dream someone will hire you to help build theirs.ö

Tony A. Gaskins Jr.

 

[KootK]

There's a blurb in the Canadian concrete manual that says "the assumption of an infinitely rigid footing (uniform soil stress) is acceptable for combined footings where the column spacing to footing shear depth ratio does not exceed 4:1". Where that came from or whether or not it should be considered gospel, I can't say.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.