Composite Steel Floors

A common method of constructing concrete floors is to use a trapezoidal steel pan onto which the concrete is poured.

The floor is relatively stiff because of the ribbing in one direction and the steel pan adds stiffness to the system by the composite action of the steel which has a high elastic modulus and is spaced away from the neutral axis. So the floors constructed this way are relatively light and stiff, not good characteristics for sound insulation generally.

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.