Page 324 - Marine Structural Design

300 Part II UItimate Strength

t Cl
20 c

Time (11

I I I I 1
0 2 s
Tmt (SI

Figure 14.6 (continued).
c. Local force-indentation relati nship for the hit tube
d. Deck displacement time history of the platform
e. Impact force time history
f. Overturning moment time history of the platform

EXAMPLE 14.6: Jacket Platform Struck by a Supply Ship
The four-legged steel jacket platform shown in Figure 14.7 (a) is struck by a 4590-ton supply
ship. Both the platform and the ship are existent structures. The ship is supposed to surge into
the platform with the velocities 0.5, 2, and 6 ms-1 corresponding to operation impact,
accidental impact, and passing vessel collision, respectively. The force-indentation
relationship for the ship bow is obtained using axial crushing elements in which a mean
crushing force applied by a rigid-plastic theory has been adopted. The local indentation curve
for the hit tubular member in the jacket platform is established following Eqs. (14.2) and