Use these add-ons so that your buildings are always on a safe footing.
The Modal Analysis add-on for RFEM 6 / RSTAB 9 allows you to determine natural frequencies and mode shapes.
In the Response Spectrum Analysis add-on for RFEM 6 / RSTAB 9, you can perform a seismic analysis using the multi-modal response spectrum analysis. Among others, the British National Annex to Eurocode 8 (BS EN 1998‑1) is implemented.
Modal Analysis Add-on for RFEM 6 / RSTAB 9 Response Spectrum Analysis Add-on for RFEM 6 / RSTAB 9