Quadratic Combination Using CQC Rule

Tips & Tricks

In RF‑/DYNAM Pro - Equivalent Loads the CQC (Complete Quadratic Combination) rule is available since version X.06.3039.

In the user interface in the tab “Dynamic Load Cases” under “Equivalent Force Analysis” there are new options for the combination of modal responses. So far, the modal responses have been combined with the SRSS rule, this quadratic combination was always applied as equivalent linear combination (formerly named as “Preserve Sign” option).

Now you have the choice between the SRSS and the CQC rule. By default, the modal combinations are applied as linear combinations which has the advantage of far smaller and signed corresponding results. But you can deactivate this option and apply the standard form of the SRSS/CQC rule if you wish.

RF-/DYNAM Pro - Equivalent Loads exports load cases for each selected mode and excitation direction. These load cases contain the required CQC parameters “Angular frequency” and “Lehr's damping.”

The formulas and additional information how to apply this rule are illustrated in the figure.


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RFEM Dynamic Analysis
RF-DYNAM Pro - Equivalent Loads 5.xx

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Seismic and static load analysis using the multi-modal response spectrum analysis