The proposed CASPPR allow a certain amount

icebreaker Ymer in 1933. Although this system is

of plastic deformation of the structure under ex-

still being used on many icebreakers, new me-

treme ice loads, and they provide factors to account

chanical and electrical transmissions have been in-

for the post-yield buckling of stiffened structures.

troduced on newer icebreakers and icebreaking

DesRochers et al. (1994) compared the stability of

cargo ships. Since 1966, the number of ships with

flat bars with that of angle sections in a stiffened

controllable-pitch propellers and mechanical trans-

structure. When a structure is designed for buck-

missions is steadily increasing. The Russian LASH

ling according to linear analysis, flat bars are

vessel Sevmorput, delivered in 1986, placed all of

avoided because angle sections have large mo-

its propulsion power on one shaft using a control-

ments of inertia to resist bending. However,

lable-pitch propeller and mechanical transmission,

DesRochers et al. (1994) found that the use of flat

thus doubling the power transmitted per shaft

bar sections increased the stability of the compos-

from 16.65 to 29.42 MW (Fig. 15b).

ite structure beyond the yield point of the mate-

One of the main reasons to use direct mechani-

rial, whereas the structural stability decreased with

cal transmission is to cut down the losses in trans-

the use of angle sections as yielding progressed