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#59936 - 08/04/14 04:10 PM ASCE7 Spectrum Gen. R values from table 12?
__Louie__ Offline
Member

Registered: 05/19/11
Posts: 33
Loc: Seattle, WA
Our client is looking for more clarification on the details of the spectrum generation built into the dynamic output processor.

The CII help for the R value in the spectrum generator says to use table 12 (value of 3.5). In ASCE, that table is for building modal analysis, not piping analysis. How is this value applied to generate the spectrum? The table in chapter 13 (Rp value is 12 for piping) is applied in a static method. Which is more conservative?

I can't seem to find any details in the technical reference manual on the R value for spectrum generation.

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#59944 - 08/04/14 10:27 PM Re: ASCE7 Spectrum Gen. R values from table 12? [Re: __Louie__]
__Louie__ Offline
Member

Registered: 05/19/11
Posts: 33
Loc: Seattle, WA
To clarify more, I'm running a dynamic analysis with an ASCE 7 spectrum. The issue seems to be the how the spectrum is being generated, specifically some confusion around the R value.

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#59948 - 08/05/14 07:01 AM Re: ASCE7 Spectrum Gen. R values from table 12? [Re: __Louie__]
Dave Diehl Offline
Member

Registered: 12/14/99
Posts: 2382
Loc: Houston, TX, USA
R appears in the denominator so 3.5 is more conservative. I believe B31E now specifies the use of 3.5.
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Dave Diehl

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#59952 - 08/05/14 11:38 AM Re: ASCE7 Spectrum Gen. R values from table 12? [Re: __Louie__]
__Louie__ Offline
Member

Registered: 05/19/11
Posts: 33
Loc: Seattle, WA
Yeah, that part I understand. How is the 3.5 determined? Any literature reference? Why isn't it 2 or 4 or 6?

Thanks!

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