Dear Sir,

You are indeed correct that UBC has changed the methodology and equations in the newer 1997 edition. The changes do make computations more difficult than in previous issues of the code.

In my opinion, most of the building Codes are setup for calculations of vertical structures and do not lend themselves nicely to piping networks and other "non uniform" structures. In static seismic analysis of piping systems, the CAESAR II input prompts for "G loading" values which are a fraction of gravity in a given direction, X, Y or Z. The program then uses these values to compute a force on the end of each element which is a product of the element's mass and the G loading value in that direction. The value of the G load ranges from 0 (no load) to about 0.4 g's (severe earthquake regions). Designers have used these values with success for quite a number of years and this method traditionally produces conservative results when compared to the more complex time history or response spectrum earthquake evaluation methods. I believe that it would be unnecessary and overly conservative to stray from G loading values that are beyond those mentioned above.

I readily acknowledge that I did not directly answer you question, but perhaps some light has been shed on how the program operates and uses these G loading factors.

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Scott Mayeux
COADE Inc.