5003 Lectures - Faculty of Engineering and Applied Science

E5003 - Ship Structures I 61
© C.G. Daley
Section Modulus Calculations
Ships are largely built of plates. This means that the moment or inertia and section
modulus calculations normally involve a collection of rectangular parts. For any
individual plate:
Ina = 1/12 t b 3
= 1/12 a b 2
Ina = 1/12 b t 3
= 1/12 a t 2
Ina = 1/12 a d 2
= 1/12 t b 3 cos 2 θ
~~~~~~
For compound sections we need to be able to find the inertia about other axes. We
use the transfer of axis theorem: