the meaning of "HPGA with a mean of AEF 1/1000"

[hello2006]

Hi Every expert,

Would you please help me to explain

" the horizontal PGA with a mean AEF of 1/1000 is 0.44 g."?
" that with a mean AEF of 1/10,000 was 0.88 g"?

I do not understand these two sentances. I do not understand "a mean of AEF of 1/1000". What is "AEF"? what is "0.44 g"?

How to use "0.44 g" in the calculation?

Thanks for any help!

 

[doct9960]

They look like seismic terms. What are you trying to calculate?

 

[hello2006]

I am calculating the piping support which will be strong enough to endure seismic load.

thanks!

 

[doct9960]

hello20065,

I am no expert at pipe support systems nor at seismic design, but I will take a shot at your question using basic physics...

I think you need to determine first the applicable acceleration (PGA) in the zone where your pipe support will be located. Let us say the zone has a 1/1000 chance of having an earthquake in a year, then you would use an acceleration of 0.44g, where g is the gravitational acceleration.

Applying the basic physics formula F=ma (force = mass x acceleration), you could get the horizontal force on your pipe support...
m - would be the mass of your pipe plus operating liquid
a - would be 0.44g

The above is just a basic force formula. The code applicable to your pipe support system may require other "factors" to be incorporated into the basic formula.

Check with your pipe stress engineer.

 

[hello2006]

Hi Doct9960,

Thanks very much for your reply!

Actually, I know my question is not the one that only expert can anser. but I mean everyone who is better than me looks like an expert in my eye. ! (to show my respect and appreciation!)

Do you mean that "AEF 1/1000" is the chance seismic can happen? Then What is "AEF"?

I definitely be familiar with F=m*a. but just not sure 0.44g means 0.44 times gravitational acceleration. Really thanks for this!

In my design, there is a room within dam, the pipe is within that room and close to ceiling about 1 meter below the ceiling. the pipe is only straight pipe with two valves in the middle. Both ends of the pipe go into the walls of the room (the walls are face to face). That is the situation of my pipe.

I am thinking that I only need to calculate weight and seismic loads. Normal water temperature, so no thermal load. What do you guys think?

Have a great weekend!

 

[doct9960]

hello2006,

To know more about PGA, AEF and other seismic stuff, I suggest you post the question to a Civil/Structural forum. They are the experts in seismic design.

 

[ukinam]

hello2006

try googling for peak ground acceleration (pga) and annual exceedance frequency (aef)

ukininam