The complete quadratic combination (CQC) rule must be applied when analyzing spatial models with combined torsional/translational eigenmodes that have adjacent modal shapes whose periods differ by less than 10%.
εij | Correlation coefficient |
with the correlation coefficient:
Di, Dj | Damping values |
r | Quotient of the natural angular frequencies (ωj/ ωi) |
The correlation coefficient is simplified if the viscous damping value D is selected to be the same for all mode shapes:
D | Damping value |
r | Quotient of the natural angular frequencies (ωj/ ωi) |
By analogy to the SRSS rule, the CQC rule can also be performed as an equivalent linear combination. The formula of the modified CQC rule is as follows: