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This page is devoted to frequently asked questions (FAQ) related to response-spectrum analysis. |
RSA definition
What scale factor is best when defining a response-spectrum load case?
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- Define one response-spectrum curve, then save the definition by selecting Save Named Set.
- Use the interactive database editor to create the remaining Named Sets, one for each plot, by editing the tables within Model Definition > Other Definitions > Named Sets.
- Display the output table by selecting Analysis Results > Structure Output > Named Set Data.
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Additional information is available in the CSI Analysis Reference Manual (Response Spectrum Analysis, page 339).
Why does the deflected shape for a linear-add load combination not look correct?
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Response-spectrum modal amplitudes (U1Acc, U2Acc, U3Acc, U1Amp, U2Amp and U3Amp) give the mode-shape multipliers which contribute to structural displacement for each direction of acceleration Acceleration. For a given mode and direction of acceleration, amplitude is the product of modal participation factor and response-spectrum acceleration, then divided by the Eigen value (ω2) of the mode. When amplitude is multiplied by any modal response quantity (displacement, velocity, acceleration, force, stress, etc.), this value represents the contribution of a given mode to the same response-quantity value reported for the response-spectrum load case.
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