Originally Posted by
Tomasz.Fudala
When this first option is selected then The modal analysis of the structure will be conducted and n vibration modes will be found.
When you select Seismic - Only modes will be set, which are important to seismic analyses, therefore those which are characterized by a large mass participation factor.
And when you select seismic pseudo modal - then Spectral and seismic analysis will be conducted using the pseudo modal method. This should be used only when applying classic analysis methods based on modal decomposition results in a very long structure analysis time.