Tipping an object over due to wind forces - Old Thread Revisited

[architrave]

thread726-296363
The tipping force thread was just what I need to reference.
Attached is a file that I was able to come up with based on this thread.
But I am afraid if I have understood the concept correctly and wonder if the concrete base weight could be smaller than what I came up with.
Any suggestion would be greatly appreciated.
Thank you.

 

[HTURKAK]

The calculation is not readable but could read the force and wt of the pole for Type A ( the first pole ).
If the wt of steel pole and concrete pad is 2009 lbs and the wind force 1100 lbs, the friction factor btw conc. pad and grade could be in the range of 0.4

So , resisting force to sliding Vr=2009*0.4= 804 lbs which is less than 1100 lbs,

I suspect the gate will probably slide rather than overturning ..

Would you consider the embedment of the gate posts similar to lighting mast ?

Pls look to the following picture ( excerpt from Foundations of structures By C.DUNHAM )

 

[strucbells]

The calculation approach shown is unfamiliar to me. They appear to be adding the stabilizing moment and the destabilizing moment then dividing by the length of the foundation and comparing to the original weight. This seems needlessly convoluted at best and inaccurate at worst.

The normal procedure for checking overturning is to subtract the stabilizing moment (Mt) from the destabilizing moment (Mw), Mnet = Mw - Mt. If Mnet > 0, then it is unstable unless you have some form of anchorage to tie it down. Keep in mind your load factors & combinations, reduce the dead load by multiplying by 0.9 (LRFD) or 0.6 (ASD) and combine with the appropriately weighted wind/seismic/etc. overturning force.