I want to design a very irregular structure taking into account the earthquakes. Does the RFEM automatically carry out the so-called modal analysis (under consideration of several forms of vibration) on the spatial system, or do I have to make a special setting for this?

Answer

The equivalent loads are determined according to the multimodal response spectrum method. To analyze a system spatially, the masses must be activated in all directions so that natural frequencies and shapes can be determined on the spatial system. Equivalent loads are then determined based on the mode shapes.

Which mode shapes are taken into account should be decided based on the effective modal mass factors. According to EN 1998-1, 90% of the structural mass must be activated to achieve accurate results.

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RSTAB Dynamic Analysis
DYNAM Pro - Equivalent Loads 8.xx

Add-on Module

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

Price of First License
580.00 USD
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

Price of First License
760.00 USD