Page 232 - Practical Design Ships and Floating Structures

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the model and Drototvoe structure:

Figure 2 : The mooring device for the test

Since the pontoon type floating structure has very thin thickness compared to length and breadth, it can
be analytically modeled as a thin plate and the hydroelastic motion of it can be described to the motion
of a thin plate. The vibratory frequency of a thin plate can be expressed as follows:

where a, EI and pA are the length, the bending rigidity and the mass per unit length of a plate,
respectively.

From the equations of (2) and (3), the bending rigidity of the model should satisfy the following
relationship in order to satisfy the frequency similarity law.
(EI), = r5 x (EI), (4)

We have performed the four-point bending tests on four specimens and the vibration test of one
aluminum honeycomb sandwich plate in the air and confirmed that the test model has the 104%
bending rigidity of the design value.

For more accurate model tests, especially in oblique waves, not only the similarity law for bending
rigidity but also the similarity law for torsional rigidity should be satisfied in principle. However, it is
almost impossible to make it so that the similarity law for torsional rigidity is not satisfied.

3 TEST CONDITIONS AND MEASUREMENTS ITEMS

As the water depths for model tests, two conditions were chosen; 0.4m and 1.3m. The water depth
0.4m corresponds to the water depth 8.0m at sea which is the real value of the water depth where the
prototype floating structure has been installed and the water depth 1.3m corresponds to the water depth
26m at sea.
Incident waves having two different angles, 0 degree and 30 degree, were chosen, and the wave
heights of 3cm, 6cm and 9cm, and the range of the wave lengths between 0.05 and 0.9 times of the
model length were generated for the tests.

Vertical displacements of the test model were measured at 39 locations using potentiometers composed