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ASCE 7 Modal Response Spectrum Analysis: Scale Spectrum or Results

ASCE 7 Modal Response Spectrum Analysis: Scale Spectrum or Results

ASCE 7 Modal Response Spectrum Analysis: Scale Spectrum or Results

(OP)
In reviewing ASCE 7-10 12.9, I see two possible ways to complete a MSRA.

Procedure A:
1. Run MSRA based on full design response spectrum
2. Scale results for R/I.
3. Scale up results for 0.85 of ELF if required by 12.9.4.2

Procedure B:
1. Scale design response spectrum for R/I.
2. Run MSRA based on elastic design response spectrum
3. Scale up results for 0.85 of ELF if required by 12.9.4.2

Are both of these ways permissible? Would they theoretically yield same results?

RE: ASCE 7 Modal Response Spectrum Analysis: Scale Spectrum or Results

For a linear analysis they will both yield the same result. And, MRSA is always a linear type of analysis.

RE: ASCE 7 Modal Response Spectrum Analysis: Scale Spectrum or Results

(OP)
Thanks Josh, glad you responded, I am RISA user and understood one flow path but am reviewing calculations from SAP user which appears to be doing it differently and was trying follow along.

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