You may find the following books useful to refer to if you need information on the methods used to calculate sections properties.
§ Roark's Formulas for Stress and Strain, 6th Edition
W C Young, McGraw Hill, New York, 1989
§ The Behaviour and Design of Steel Structures
N S Trahair and M A Bradford, Chapman and Hall, London, 1988
§ Formulas for Stress, Strain and Structural Matrices
W D Pilkey, John Wiley and Sons, New York, 1994
§ Elements of Strength of Materials
S P Timoshenko and D H Young, Van Nostrand, 1968