Dear All,

Just a simple question, is Peak ground acceleration (PGA)the Uniform Load input in CaesarII?

I have a project with given PGA of 0.06g. Can I use it as the seismic uniform load for the UG pipe input?


Thanks in advance.

The peak ground acceleration need not be the acceleration used in design.
There's usually an amplification factor that considers how close the piping system's natural frequencies are to the supporting structure's natural frequencies, a response modification factor to address the piping ductility, an importance factor and the elevation of the piping in the supporting structure.
The terms I mention are from ASCE 7. Your local design code may be different.

Thanks Dave for the explanation.

I'm following the client's specification which mainly accordance to 1997 Uniform Building Code (UBC).

They states some factors and coefficients such as:
Peak ground acceleration (PGA);0.06g.
Seismic zone factor; Z=0.075
Seismic importance factor; l=1.25, lp=1.5
Soil profile type; SD.
Seismic coefficients; Ca=0.12 and Cv =0.18.

Then following by set of calculation. At the end of the calculation, they stated formula of (32-1) to be result in Fp = 0.72Wp.

So, can I just take the value as the 0.72g for the Caesar II uniform load input?

I think it's better to study a very good article on the subject, where Mr. Diehl has explained very well the basics.
Please see
http://www.coade.com/Uploads/mechanical-engineering-news/oct02.pdf

After that you may review the calculation leading to 0.72g for UBC Zone I.

Regards,

Equation (31-1) of UBC 1997 is easier to apply but gives conservative results as it considers that the non-structural element will be subjected to four times the peak ground acceleration irrespective of its locations in the building.
In that formula Ca = horizontal seismic coefficient (basically the peak ground acceleration) for a particular soil profile type and zone factor. The "response" of non-structural element isn't considered by (31-1).

On the other hand, Equation (31-2) which can be alternatively considered, it's more accurate as it considers different parameters on which the response of non-structural elements is dependent (that's why Ca is replaced by Ca*ap/Rp).
It assumes (conservatively enough) that a non-structural element attached to the roof of a building will experience four times the acceleration that a similar element attached to the ground floor of the same building experiences (i.e 4*Ca*ap/Rp vs. Ca*ap/Rp).
That's why it considers a trapezoidal distribution of floor accelerations, linearly increasing from the acceleration at the ground to the acceleration at the roof- this is the factor 1+3*hx/hr.

I would recommend you (31-2) if you have the freedom to consider it. In my opinion (31-1)is very conservative.

Please note that what I've written is related to piping as "non-structural" i.e is attached to or housed in a "building" or "building system", (of course) being not part of the main load-resisting structural system of the building....

Best regards,