Section modulus is a measure of the shape of the crosstie and is calculated by dividing the MOI by the greatest distance of the section from the neutral axis, calculated from dimensions and rectangular cross-section.
Section modulus is a term that not many people are familiar with, but this term is something that bending and rolling companies deal with on a daily basis. Section modulus is a geometric property for a given cross-section used in the design of steel beams or flexural members. The relationship between many geometric properties such as tension, compression and shape of the member lead to the calculation of its section modulus.