Hey All, This is my first post here, and am new to the website and im hoping someone can help me with this.... Im trying to work out the basic calculations required to calculate the moments of inertia on curtain walling when a wind load is applied. The company I work for has many different calculation softwares, which will give me the required Ix, Iy & Wx etc. The values I input into the calculator are as follows... Span (L) Width Left (B1) Width Right (B2) Longest Glass Edge (L1) Wind load i.e 1.2 (kN/m2) L/* - Being glass it varies on type i.e L/250 for a span above 7.5m (glass defiant). Material E-Module - 21000000.00 - kg/m2 (Steel) Tension Perm. - 1600.00 (Steel) With the above information the software as I stated before give me the required profile Ix (surface moment of inertia in cm^4) & Wx (section modulus in cm^3). The profiles used are for curtain walling (facades) for which the profiles used (tubes etc) have their independant static properties, which we cross reference to the calc. output. I need to know how the software package calculates this in very basic equation terms..... A walk through would be very very appreciated! Thanks for your help! If you require any further information, please post and I will try to find relevant parts etc. Andy.