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Re: 1997 UBC Question

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Your elevated piece of equipment is an ELEMENT of a STRUCTURE, i.e., the
structure supports the element

h-sub-x is the ELEMENT attachment elevation

h-sub-r is the STRUCTURE elevation with respect to grade.

See the 1999 SEAOC Blue Book, Section C107 for more extensive background.

See the SEAOC Design Manual Volume 1, Examples 37 and 38 for sample


Rick Drake, SE
Fluor Daniel, Aliso Viejo


"Ritter, Mike" <mritter(--nospam--at)> on 01/31/2000 08:32:17 AM

Please respond to seaint(--nospam--at)

To:   "'seaint(--nospam--at)'" <seaint(--nospam--at)>
cc:    (bcc: Rick Drake/AV/FD/FluorCorp)

Subject:  1997 UBC Question

List members,

I could use a little help interpreting the 97 UBC.  A colleague has
prepared a set of calculations to evaluate an elevated piece of
equipment, and has used section 1632 of the 97 UBC (Lateral Force on
Elements of Structures, Nonstructural Components and Equipment Supported
by Structures).  Specifically I have a question regarding the definition
of hx and hr.  hr is defined as the structure roof elevation with
respect to grade.  Is this the main building structure roof elevation or
the equipment structure roof elevation?  It appears that the ratio of hx
and hr is to make the seismic demand larger if the equipment is higher
in the building (makes sense) but I can read the hx definition two ways.

Anybody got the answer?

Thanks in advance,

Michael Ritter, PE