W = weight per unit length (lb/ft or kg/meter for metric )
A = cross sectional area (in^2 or cm^2 for metric)
Ix = moment of inertia about the x (horizontal/strong) axis (in^4 or cm^4 for metric)Iy = moment of inertia about the y (vertical/weak) axis (in^4 or cm^4 for metric)http://en.wikipedia.org/wiki/Second_moment_of_area
Sx = Section Modulus about the x axis (in^3 or cm^3 for metric)Sy = Section Modulus about the y axis (in^3 or cm^3 for metric)http://en.wikipedia.org/wiki/Section_modulus
Note: At this time, only the weight property is used by Bentley Structural. The rest of the properties are loaded into memory but never used. The use of the weight property is limited to the calculation of the total weight of the member (= weight/unit length X length) in the Structural Quantity Report Spreadsheet.