Square Root of the Sum of the Squares Method - CAESAR II - Help

CAESAR II Users Guide (2019 Service Pack 1)

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CAESAR II
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CAESAR II Version
11.0 (2019)

This method defines the total system response as the square root of the sum of the squares of the individual modal responses. This is effectively the same as using the double sum method with all correlation coefficients equal to 0.0, or the grouping method with none of the modes being closely spaced. The total system response is calculated as:

This method is based upon the statistical assumption that all modal responses are completely independent, with the maxima following a relatively uniform distribution throughout the duration of the applied load. This is usually non-conservative, especially if there are any modes with very close frequencies, because those modes will usually experience their maximum DLF at approximately the same time during the load profile.

Because all time history combinations are done algebraically (in-phase), this modal combination method has no effect on time history results.