Scaffolding equations?????

Guys. I have been looking on a lot of engineering books and i couldn't find what is the formula to calculate the stress and the bending moment onto the scaffolding. anyone know which is the equations? plz i really need it...

Calculate the stress on to the pipe of the structure and the bending moment onto the upper part of the pipe which place the platform to support people. Thank you.

I had no idea on the equation to calculate.