ISO scantling rules

[pashbe1]

Hi,

is anyone familiar with the ISO scantling rules for small craft part 5. I need to figure out (settle an argument) if in section 9, 9.1 requirements for stiffeners w/ similar materials and section 9.2 Requirements for stiffeners w/ dissimilar plies are mutually exclusive.

9.1 reads "The minimum section modulus of stiffening members including the effective plating and the web area of the stiffening members shall not be smaller than given by the following equation"

9.2 reads "Dissimilar plies are when mechanical properties differ by more than 20% from eachother. For such stiffeners, the allowable bending moment does not necessarily correspond to the stress at the farthest fibre of the neutral axis. Therefore the criteria shall be the allowable bending moment, the required sumEI and allowable shear load. The value of Md (Fd) is that value of bending moment (shear force) which corresponds to the first ply in the laminate stack reaching the allowable design stress for that ply."

Any ideas?