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RE: Story Drift: 1994 UBC vs. 1997 UBC

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Bill:

I believe that you should be "concerned about non-structural, 
collateral damage to glazing, finishes, etc."

If you are concerned about these problems for non-seismic loads, you 
should consider the deflection of the structure due to the 
application of the design loads.  If you are concerned about these 
conditions under seismic loading, you should consider the expected 
total displacement (including inelastic response).

The 1997 UBC indicates that this displacement is 0.7R times the 
displacement due to the design forces. As Ron pointed out, even this 
estimate is probably on the low side; UBC writers don't want to say 
1.0R because it might scare people even more.

Again, the important point to stress is that checking the 
displacements due to reduced design forces is meaningless.  Thus the 
code has changed.

-Mike


> From:          "Bill Allen" <Bill(--nospam--at)AllenDesigns.com>
> Subject:       RE: Story Drift: 1994 UBC vs. 1997 UBC
> Date:          Thu, 12 Aug 1999 10:26:34 -0700

> Sooo... in a wood framed structure with 8 ft. plate heights on a wall with a
> LOT of glazing and containing inverted pendulums, flag poles or cantilevered
> steel columns (whatever term is preferred), is it in fact allowable to
> design to a drift of 0.011*8*12 = 1"? Are the design loads such that we no
> longer are to be concerned about non-structural, collateral damage to
> glazing, finishes, etc?

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Michael Valley                                   E-mail: mtv(--nospam--at)skilling.com
Skilling Ward Magnusson Barkshire Inc.                  Tel:(206)292-1200
1301 Fifth Ave, #3200,  Seattle  WA 98101-2699          Fax:        -1201