Hi* I'm designing a rectangular nozzle 512mm x 512mm with a corner radius of 20mm* and thickness 6mm according to ASME. I'm referring to Appendix 13 sketch (3)* and a bit confuse on the terms;

1) c : distance neutral axis of cross section to extreme fiber
2) I : according to formula I = bt^3/12* b=1.0 (App. 13-7)

Hopefully someone can helps. Tq.