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Re: Table 16-O - Horizontal Force Factors, ap and Rp

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My understanding is that section 3.C applies to "flexible" equipment
anchored below the center of mass.  I think this was published as an errata
to the 1997 UBC, I can't find the errata sheet at the moment, but this is
what is hand written in my code book.  You should be able to verify with


----- Original Message -----
From: From the desk of Joe Otto <jmo_engineering(--nospam--at)>
To: Seaint@Seaint. Org <seaint(--nospam--at)>
Sent: Thursday, August 26, 1999 2:01 PM
Subject: Table 16-O - Horizontal Force Factors, ap and Rp

> On one of our jobs, we're installing some air conditioning package units
> top of a typical panelized roof.
> We used a value of 1.0 for ap as required by 3.B in Table 16-O (page
> We received a plan check comment indicating that the value of ap should be
> 2.5 because the attachment of the unit is below its center of mass as is
> required by 3C.  If I use the 2.5 value, I get a value which is greater
> that required for emergency power systems (3.D) and containers with
> flammable hazardous materials (3.E).
> Both parts of the code appear to apply?  Can anyone clarify when 1.0 or
> are truly intended to be used.
> Thanks in advance.
> Joseph M. Otto, PE
> Ireland Engineering
> Fremont, CA