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re: amusement structures

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At 01:51 PM 01/04/2000 -0800, you wrote:
>Thanks for the responses. I think I should have been a little clearer in 
>what I was looking for. My main concern is the UBC's stipulation that these 
>type of structures can be designed with a rho=1.0. I don't understand where 
>the redundancy in the cantilevered column system is. If it were to have to 
>be designed with a rho=1.5, then seismic would govern the design in my 
>Aaron J. Burkhardt, P.E.
>KPFF Consulting Engineers
>Portland, OR

Why not check out commentaries to the SEAOC "Blue Book" and /or to any other
of the alphabet soup agencies mentioned in recent weeks that write or
dictate seismic code.

It might be that no particular degree of redundancy was ever expected when
the rather stout seismic factors for non-building structures were settled
on. It might be that committee members admitted that not enough was known of
the range of possible non-building structures (as they failed to admit for
woodframe houses) to make refinements such as rho factors appropriate.

There is always the option of weighing what the codes and commentaries say
about somewhat similar structures, plus considering the peculiarities of the
structure at hand, then considering the occupancy for its heartstrings pull,
and proposing your own good-faith interpretation of what ought to be. That
kind of exercise is still called engineering. 

As far as the oft-used code buzzword "rational" is concerned, my Webster's
says it essentially means "derived from reasoning". To consider the whole
range of concerns, including probable public expectations, is therefore
consistent with being rational.

I agree with others that wind may control for property loss, but seismic may
be more meaningful for certain Achilles' heel elements/ connections and for
life safety.

Charles O. Greenlaw SE   Sacramento CA