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Under the Missing Mass Combination drop down listing, only the SRSS and Absolute SUM method appear as choices. Where is Modal?
Answer: As seen in the online help:
The Modal method is only available for the Uniform Support Response Spectrum (USRS) option. If Modal is selected as the combination method while the MSRS option is disabled (unchecked), and then the MSRS option is enabled (checked) the combination method selection will automatically change to SRSS.
Under load; Response force spectrum Selecting seismic code EURO The values displayed in the result is correct for input: Gravity but changing the input to Acceleration the values need to be multiplied by 25.4, is this correct?
Answer: Yes, Response Spectrum, Seismic codes acceleration is wrongly listed for SI units. This issue was repeatable in AutoPIPE 09.06.00.15 and will be fixed in the next version of the application. Logged under CAE-TR-11092.
When performing a Dynamic response spectrum analysis it is recommended to select "ZPA" option to capture maximum static or dynamic results. Also, Select "Missing Mass" to Capture additional Modal Mass beyond the Cut-Off Frequency.
If you did not know, AutoPIPE has a nice interpolated spectral report found in the "Analysis Summary" sub-report. This reports the intersection of the modal frequencies with applied response spectrums but also calculates the ZPA acceleration.
Again, AutoPIPE calculates the Zero Period Acceleration, (ZPA) which can be defined as Static Seismic (Sg) Load at ground level. This is same as Peak Ground Acceleration (PGA)
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