Page 307 - Practical Design Ships and Floating Structures

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preventing an increase of resonance frequency, which would constitute a serious security problem

Expected downtime due to
sign. acceleration > 0.0259
0.8 ffcla56
BL initial design 5.0 7.0 8.a 11.0 ma 15.0 17.0 1g.a 21.0 21.0
In[ml a.a 5.a 7.0 9.0 11.a 15.0 i5.a 17.0 10.0 21.0

.-
a
a '$ [infeasiblesea states)
1
0 a
a a
1 1 a
7
3 a a a __
0
a
72 -5s- - 5% ,- -1 - -
a
248 I 'Ea 191 43 ..
1
181 2 3 4 3 1 6 5 1 1 1 0 e
199 10 [feasibleseastates) 0
a
0 30 60 90 120 150 180210240270300330 sa 0
North East South Wesl
direction of wave origin p [degrees]
Figure 6. Result of downtime minimization of a semisubmersible
RAOs of surge motion RAOs of heave motion
0.75 1.50
0.6 - optimized design - 1.20
I I
0.45 0.90
0.3 0.60
t;p e-
o
v1 0.15 (o 0.30
. .. .... . . . . .... .
....-
0 I 0.00
0.2 0.4 0.6 0.8 1 '
wave frequency w [radls] wave frequency w [rad/s]
=Os of roll motion 0.75 -." RAOs of pitch motion
- 0.75 . ... ::. .,,. , - """' I
. . . . . . . . . . initial design
5 0.6 o@mized design 5 0.6 - oDtimized desian
m m
D wau,e heading 120 deg D wave heading 120 deg
0.45 0.45
. . ,... -.. . .
0.3 0.3
v 0
0.15 3 0.15
v1
n n
0 0.2 0.4 0.6 0.6 1 1. 0 0.2 0.4 0.6 0.8 1 1
wave frequency w [rad/s] wave frequency w [radls]
Figure 7. Comparison of motion behaviour of initial and optimized semisubmersible.
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