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RE: amusement structures

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Aaron,

In response to your concerns regarding the amusement structures and
designing the column base connection for omega level forces, I would suggest
that if the designer has used the cantilever column value of R=2.2 (item 5,
Table 16-N) rather than the Ordinary Moment Frame value of  R=4.5, then the
omega factor required by Section 2213.6 for ASD (who uses anything else?)
would not apply.  Using both R=2.2 and the omega  factor seems more than
intended by the code.

Jim Persing
Redmond, WA

-----Original Message-----
From:	Aaron Burkhardt [mailto:aaron(--nospam--at)kpff.com]
Sent:	Tuesday, January 04, 2000 9:08 AM
To:	'seaint(--nospam--at)seaint.org'
Subject:	amusement structures

Is anyone familiar or had experience with "amusement structures"? I am
reviewing some calculations for a waterslide structure and they have
omitted all seismic calculations (we are in seismic zone 3) with a blanket
statement "wind load governs" (we are only 80 mph,  exp. B). The load
comparison done shows the seismic and wind loads to be somewhat close in
value. In section 1634.1.2 it states that the redundancy factor may be
taken as 1.0 for non-building structures. If there was a structural system
that is not redundant, wouldn't a cantilevered column system such as this
be it? Looking through he table 16P all the non-building structures are
generally not going to have hundreds of children running over them at any
given point in time, so that is the reason I am concerned. Also, in a
cantilevered column system, shouldn't the base plate weld to the column and
the plate itself be subject to omega level forces and the detailing
requirements of chapter 16 and 22?

Thanks,

Aaron Burkhardt, P.E.
KPFF Consulting Engineers
Portland, OR