The different stiffnesses in the directions parallel and perpendicular to the steel profile give the floor different critical frequencies in each direction, that is the panel is orthotropic Calculation of the bending stiffnesses in each direction is not straight forward because the steel adds to the stiffness as do the corrugations. INSUL uses a method published in ANSI/SDI C-2011 Standard for Composite Steel Floor Deck - Slabs.
The parameters of the floor are entered in the materials editor (and can temporarily be
modified in the properties editor).