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RE: amusement structures

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If it is close, you need to run the analysis once for wind and once for
seismic.  Wind has to govern by a large margin in order to ignore local
seismic effects.  And yes you need to design for the omega level forces.  

I would further suggest that the anchor bolts be tensioned to the omega
level forces on the anchor bolts.  I prefer a headed anchor bolt and a
wrapped and greased shaft.  Anchor bolt stretch accounts for much of the
actual lateral drift of cantilevered structures.

Keep in mind that it is very unlikely that a design wind event will occur
with people on an amusement structure due to weather forecasting and the
nature of extreme winds.  However we can not predict when the design seismic
event will occur.

Harold Sprague

> -----Original Message-----
> From:	Aaron Burkhardt [SMTP:aaron(--nospam--at)]
> Sent:	Tuesday, January 04, 2000 11:08 AM
> To:	'seaint(--nospam--at)'
> 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