Page 325 - Marine Structural Design

Chapter I4 qffshore Structures Under Impact Loads 301

(14.7). Both indentation curves are hrther approximated as multi-linear curves. First, a linear
static analysis is carried out for the gravity loading and after, a nonlinear dynamic analysis is
performed which includes fluid-structure interaction, soil-structure interaction, large
displacements, and plasticity and kinematic strain-hardening effects for the affected platform.
The time history of the impact deflections is shown in Figure 14.7 (b). Figures 14.7 (c-e) show
how the energy is shifted between the ship and the platform and between kinetic energy,
elastic deformation energy, and plastic deformation energy.
Using the present procedure, impact forces, dent in ship, and local dent depth of the hit
member, can be obtained, provided the impact velocity and indentation curve of the ship are
known. The main results of the example are listed in Table 14.2.
Finally, the distribution of the plastic nodes for an impact velocity of 5ms-1 at time 1.45s is
shown in Figure 14.7(a).

Table 14.2 Main Results of Ship-Jacket Platform Collisions