Tipping force of Wind
Tipping force of Wind
(OP)
I have a pretty basic question but i have hit a road block.
I have a concrete wall that is 14'Lx1'Wx7'T that is sitting on another reinforced concrete slab.
Using IBC 2009 for my region the Basic Wind Speed for design is: 90 mph (normal to wall surface). With this the Wind Pressure is: 20.7psf.
I calculated the tipping force of the wall to be 1,050lbf at the top of the wall with no slipping.
Sum of moments = 0, p=Tipping Force; W=Weight of Wall W=(98Cuft*150lb/Cuft=14,700lbs)
0=-P(7)+14,700(.5) P=1,050lbf
Where i am having trouble is determining if the pressure force is enough to tip the wall over. I know the wall area is 96sqft but i think 20.7*96=2,020lbf cannot be considered a concentrated load that would cause tipping cause the force on the bottom half of the wall is going to cause the wall to slide before it causes it to tip over. Do i only consider the top half of the wall in the tipping?
It seems illogical that a 90mph wind could tip a 1'thick concrete wall thats only 7'x14'...
I need help please!!!
I have a concrete wall that is 14'Lx1'Wx7'T that is sitting on another reinforced concrete slab.
Using IBC 2009 for my region the Basic Wind Speed for design is: 90 mph (normal to wall surface). With this the Wind Pressure is: 20.7psf.
I calculated the tipping force of the wall to be 1,050lbf at the top of the wall with no slipping.
Sum of moments = 0, p=Tipping Force; W=Weight of Wall W=(98Cuft*150lb/Cuft=14,700lbs)
0=-P(7)+14,700(.5) P=1,050lbf
Where i am having trouble is determining if the pressure force is enough to tip the wall over. I know the wall area is 96sqft but i think 20.7*96=2,020lbf cannot be considered a concentrated load that would cause tipping cause the force on the bottom half of the wall is going to cause the wall to slide before it causes it to tip over. Do i only consider the top half of the wall in the tipping?
It seems illogical that a 90mph wind could tip a 1'thick concrete wall thats only 7'x14'...
I need help please!!!






RE: Tipping force of Wind
http://www.eng-tips.com/threadminder.cfm?pid=507
and brace yourself for the backlash..
BTW.. a sketch would help.
RE: Tipping force of Wind
The thread you posted just takes me to main board that I searched...
Also the wall is freestanding... it can be assumed to not be tied in on any side or top and is resting on a flat concrete surface.
Thanks!
RE: Tipping force of Wind
They're ripping a guy who posted a very fundamental question a new one on this thread:
http://www
What I mean is that you're likely to get some responses in the same tone as on that thread.
Post a sketch and it's likely you'll get a better response.
I don't really know what you mean by "tipping force". There are several failure mechanisms for the problem you describe. A 1 ft. wall is very large; where are you getting these dimensions? How is the wall reinforced? how is it connected to the slab below? How are you getting that wind load?
RE: Tipping force of Wind
Overturning moment = 2028*7/2 = 7098'#
Stabilizing moment = 14210*0.5 = 7105'#
The wall is in imminent danger of tipping over. The factor of safety is 7105/7098 = 1.001 which is inadequate. It should be at least 1.5 to satisfy most building codes.
BA
RE: Tipping force of Wind
RE: Tipping force of Wind
He is asking if the wind pressure is enough to tip the wall over. Without reinforcement, it is just about enough to tip it. If there is reinforcement between the wall and the slab below, it could be a different story, but the amount and position of the reinforcement would need to be known in order to come up with a sensible answer.
BA
RE: Tipping force of Wind
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask
RE: Tipping force of Wind
You can't alter the basic statics; for each failure mode destabilizing force with appropriate ultimate factor should be below stabilizing force with code recommended reduction factor.
When checking overturning:-
Tipping moment caused by wind pressure on full area of the wall x ultimate load factor + other lateral force that your code may require should be less than the resisting moment due to dead weight with ultimate reduction factor.
RE: Tipping force of Wind
I live and practice in a high wind area. A 90 mph wind can do a lot of damage and can easily tip over a freestanding wall that is not sufficiently tied to its foundation or slab.
I'm assuming this is a fence or a screen wall. It might come under a lower category of structure, but nevertheless, it needs adequate resistance to overturning, which it currently does not have.
RE: Tipping force of Wind
This wall will be tied into slab below with #5 rebar. The wall also will have a double cage of #5 with 1' centers H&V.
I think this should be enough but I'll find out next week when I have my civil/structural guy take a look...
Your thoughts/opinions are welcome and will be heeded...
RE: Tipping force of Wind
RE: Tipping force of Wind
RE: Tipping force of Wind
RE: Tipping force of Wind
The wind pressure is applied at the mid-height of the wall under ASCE 7's case A. There is also a case B and C that might apply - Case B has the load shifted upwards slightly from the middle of the wall.
If you are the responsible party designing this wall the I would suggest you get someone (like you mentioned - a civil/structural) friend to look at it.