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SERM 6 Example 7.13


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#1 hank89

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Posted 23 March 2012 - 03:53 PM

SERM 6 page 7-27 indicates the Cs value for T<TL be determined by ASCE eq 12.8-3 and the maximum value be determined by ASCE 12.8-2.

I have always used equation 12.8-2 to determine Cs and equation 12.8-3 for the maximum (provided T<TL; which it is for most low rise buildings.

Thoughts?

In addition, Cs min in not 0.01 per 12.8-5, this was changed to 0.044Sds I >=0.01 per asce7-05 supp#2

#2 McEngr

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Posted 23 March 2012 - 08:34 PM

Page 7-27 states it correctly. The best thing to do is reference the Sa chart and take out the I/R to determine where you are along the curve based on your period, T or Ta.

#3 hank89

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Posted 24 March 2012 - 12:12 AM

Page 7-27 states it correctly. The best thing to do is reference the Sa chart and take out the I/R to determine where you are along the curve based on your period, T or Ta.


Thanks McEngr... following the Sa chart is the way to go, I was just following the text of ASCE7 on page 129. I've learned a bunch while studying for this exam!

BTW the SERMS definition of "wind borne debris region" on 7-42 states "region in Hawaii that is within 1 mi of the coastal high water line and where the basic wind speed is at least 110mph."...
this is not correct.

IBC 2009 states "hurricane prone regions that are within 1 mile of the coastal mean high water line where the basic wind speed is 110mph or greater; or portions....120mph; OR hawaii"

#4 McEngr

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Posted 25 March 2012 - 02:18 AM

I've designed buildings in Hawaii and they follow their own rules... they use a Kzt factor, exposure factor, and wind speed on maps produced by the building department locally for the big island. Ultimately the locals overrule whatever the code says, of course. :) Thanks for the further "errata" updates. :)

#5 dakota_79

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Posted 25 March 2012 - 06:59 PM

Thanks for the catch on the erata, Hank.

Yeah, with that graph McEngr noted in mind, my procedure is usually to calc Ts=Sd1/Sds. If T<Ts, then 12.8-2 controls by inspection. If Ts<T<Tl, then 12.8-3 controls by inspection. Just a minor shortcut / timesaver (on the order of a few seconds, but every little bit counts!).




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