My piping system for analysis is located in California, seismic Zone 4. In the past I have used .463g for U when performing static equivalent seismic analysis. A consultant says to use .368g for the y direction, and .836g for the x and z direction. Any comments or suggestions?

Ed,

The bottom line is that the base shear values using static method and the dynamic analysis should match.

Is your project based on IBC 2000? The IBC 2000 gives a more detailed response spectrum method than the previous UBC 1994/1997.You can go through an excellent atricle on this topic in the latest Newletter of COADE ( OCT 2002 ).

Based on the code( IBC/UBC) that you are using for your project, perform a dynamic analysis and check if the base shear matches w.r.t the numbers provided by your consultant.

Since you are from California, the UBC response spectrum ( and also IBC )is very very authentic ( which I would look with doubt for say India ) , so the comparison of static /dynamic base shear coeffients is the nbest method suitable for you to check the authenticity of the data provided by your consultant.

When making the comparison follow the guidelines provided in the technical article I mentioned before.


A.Bhattacharya

Stress Analyst

Bechtel Corporation

G factor is calculated from Design Spectral Response Acceleration (short period) for the particular site and is usually furnished by the owner. It is also a function of component amplification,response modification,importance factor and the point of support attachment inside the building structure.

Hi Ed,

It also might be a site specific requirement if it is a government facility.

There is MUCH good free info at this address:

http://www.llnl.gov/es_and_h/hsm/doc_22.04/doc22-04.html#27.5

Regards, John.