AISI S100 Box Section Saint-Venant Torsional Constant Clarification 1

[torres_303]

Hi everyone. I have a question in regard to AISI S100-16. The equation to calculate the Saint-Venant constant J which is given in the commentary section as equation C-F2.1-9 and there are two variables in the equation "a" and "b" which are defined as:

a = Distance between web centerlines
b = Distance between flange centerlines

Can someone explain to me the actual centerline they are referring to? I am checking a box section, meaning a stud section within a track to create a box section. I am trying to calculate the combined J value for the built-up section. I included a snip of the section where the equation is described. TIA

 

[KootK]

The distances just define the width and height of the box, taken to the centerline of the plate elements that form the perimeter of the box.

 

[torres_303]

@KootK Thanks so much for clarifying that for me.