Foundation of a Tower - Moment in two directions - Overturning control
Foundation of a Tower - Moment in two directions - Overturning control
(OP)
Hello everyone,
Consider a spread foundation, supporting a tower used for powerlines. The foundation is rectangular, and I have two moments acting simultaneously parallel to X and Y directions. (i.e. the resultant moment is diagonal, not parallel to the breadth or length of foundation).
I have two questions:
- How can I check if there is risk of overtunring, without computer modeling? Is there any handy equation (similar to what we use for single moment case), showing that the vertical load locates inside the central 1/3 zone of foundation?
- Do you use or know any specific Code for designing foundation of powerline towers?
Thanks in advance for your time and attention.
Nik





RE: Foundation of a Tower - Moment in two directions - Overturning control
You will need to check the x,y and diagonal conditions, independently. If your foundation is sufficiently ridgid so that bending is neglible, the analysis is fairly straightforward. If bending is there, it's a little more complicated, but not greatly so.
RE: Foundation of a Tower - Moment in two directions - Overturning control
Don't forget to consider the unbalanced line condition and also the consideration that overturning usually doesn't occur inline with the lines.
RE: Foundation of a Tower - Moment in two directions - Overturning control
RE: Foundation of a Tower - Moment in two directions - Overturning control
Hi Ron and thank you so mich for your reply.
Would you please explain more what did you mean by "the unbalanced line condition"?
RE: Foundation of a Tower - Moment in two directions - Overturning control
_____________________________________
I have been called "A storehouse of worthless information" many times.
RE: Foundation of a Tower - Moment in two directions - Overturning control
DaveAtkins
RE: Foundation of a Tower - Moment in two directions - Overturning control
RE: Foundation of a Tower - Moment in two directions - Overturning control
RE: Foundation of a Tower - Moment in two directions - Overturning control
I agree with your approach, except with a footing, there cannot be any uplift. If outside the kern limit, then
P/A +/- Mc/I +/- Mc/I does not apply anymore.
DaveAtkins
RE: Foundation of a Tower - Moment in two directions - Overturning control
RE: Foundation of a Tower - Moment in two directions - Overturning control
What happened to my factor of safety (of the allowble bearing capacity)?
A little tongue-in-cheek tonight.
RE: Foundation of a Tower - Moment in two directions - Overturning control
RE: Foundation of a Tower - Moment in two directions - Overturning control