FAQ 001485 EN

Calculation DYNAM Pro - Equivalent Loads RF-DYNAM Pro - Equivalent Loads

Because I have to design a very irregular structural system for earthquakes, I would like to know if RFEM performs the so-called modal analysis (considering several mode shapes) automatically on the spatial system, or if it needs a special setting.

Answer

The equivalent loads are determined according to the modal response spectrum method. To find out how many mode shapes must be considered, it is useful to calculate the equivalent mass factors in module window 1.6 additionally, because it is basically recommended to take as many modal shapes that the sum of the effective equivalent masses is at least 90 % of the effective total mass.

RSTAB Dynamic Analysis
DYNAM Pro - Equivalent Loads 8.xx

Add-on Module

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

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