Combination Rules when Considering Accidental Torsion

Tips & Tricks

When accidental torsion is considered in the module RF-/DYNAM Pro - Equivalent Loads, the module exports two load cases for each eigenvalue: one with positive torsional moment, and the other with negative torsional moment.

Load cases exported from RF-/DYNAM Pro are combined with the SRSS or the CQC rule. The two torsional load cases have to be combined as alternative group, using OR. Here it is important to note, that the absolute values of the considered results are used for comparison.

The ‘equivalent linear combination’ works also when accidental torsion is considered. Therefore the alternative combination has to be applied when calculating the factors f used for the ‘Preserve Sign’ option.

Formulas and an example are provided in the figure.

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

Add-on Module

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