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RE: UBC Eq. 30-1

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Ev should be applied as a vertical load and Eh as a horizontal load. I think
the 1997 UBC code is somewhat confusing in presenting E = Eh + Ev with E
referred to as "the earthquake load". This should rather be presented as two
components to a load combination rather than as a single load. I have
reviewed other designs which have misinterpreted this as a combined
horizontal load. Although Ev refers to "the load effect resulting from the
vertical component of the earthquake ground motion", it could be interpreted
as a horizontal effect due to vertical motion, perhaps similar to a Poisson
effect.  

UBC also states to add the effect to the dead load effect, which can be
misinterpreted as acting in only an additive direction. However, vertical
acceleration acts both downward and upward and thus the vertical
acceleration effects should be taken in the most critical direction as
applicable to the element. Thus, one "adds" either a positive or negative
number. 


William C. Sherman, PE
CDM, Denver, CO
Phone: 303-298-1311
Fax: 303-293-8236
email: shermanwc(--nospam--at)cdm.com


> -----Original Message-----
> From: RainCat1(--nospam--at)aol.com [mailto:RainCat1(--nospam--at)aol.com]
> Sent: Wednesday, September 11, 2002 2:18 PM
> To: seaint(--nospam--at)seaint.org
> Subject: UBC Eq. 30-1
> 
> 
> In the UBC Eq. 30-1 E=rhoEh + Ev, what is the direction for Ev?
> Are we suppose to combine numerically the expressions rhoEh & 
> Ev? Thanks!
> 

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