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I'll take a shot at this.

Figure the base shear from section 1630.2 and distribute it to your members
as you normally would.  When you go to evaluate a single member (beam,
column, brace, ect.), figure the E load component from equations 30-1 or
30-2 as apropriate.  Then use this E in your load combinations from section
1612.  Equation 30-2 is similar to the 3Rw/8 multiplier that we are used to
from 1994 UBC.  It is applied in the same situations (discontinous systems,
connections, ect) and also now explicitly includes drag struts.  Keep track
of your design method (strength or ASD) when plugging into the load
combinations.  Your forces from equations 30-1 and 30-2 are in a strength

The reason for equation 30-1 is to provide a method for penalizing less
redundant structures and it comes directly from the research into the
Northridge earthquake.  It is assumed that a redundant structure is more
reliable during a seismic event due to load redistribution.  It also
includes a term for vertical forces, but this gets washed in the load

I hope that this was helpful,

Curt La Count
Jacobs Engineering
Portland, OR
From: rlewis(--nospam--at)
To: seaint(--nospam--at)
Subject: Seismic - UBC 1997 Application
Date: Tuesday, June 08, 1999 1:59PM

I sent a similar message to the list yesterday, but only received one
response.  I am still confused.  No offense Ben Yousefi, I did very much
appreciate your input, I'm just still confused.  Now somebody has got to
understand this code and be able to explain it to an average engineer like

Some background, I thought 1997 UBC took care of the change from ASD to USD
through the R factor and other adjustments.  I don't understand why
30-1 and 30-2 are there.  Do they apply to all designs?

Equation 30-2 multiplies Eh by the omega factor.  I am designing a concrete
SMRF structure.  Omega is 2.5.  Therefor Em is equal to 2.5 Eh, which I
believe is the base shear.  So does this mean I multiple the base shear by
2.5 for my member design?  If I am running load combinations in my frame
analysis, do I add this factor to the combinations?  It seems I am
the shear quite a bit, although it was already suppose to be at strength

Any insight into this would be helpful.