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APPLICATIONS OF MULTI-DEGREE OF FREEDOM ANALYSIS
Figure 9.5 Two degree of freedom model of a monotower gravity platform on an
elastic foundation.
Table 9.2 System Parameters and Results for the Monotower
Soil modulus
Soil density; Poisson’s ratio
Soil stiffness, sliding
Soil stiffness, rocking
Structural mass, virtual
Structural mass, actual
Structural mass, buoyant
Structural inertia, virtual
Structural inertia ratio
Center of actual mass
Center of buoyant mass
Caisson radius
Gs = 10 MPa
ps — 2000 kg/m3; ia, — 0.33
fci = 2.16 x 109 (1 - 0.0318cjo) N/m
k0 = 3.63 x 1012(l - 0.137cuq) N-m
m = 6.15 x 108 kg
m0 = 3.56 x 108 kg
mb = 2.59 x 108 kg
J g — 8.80 x 1011 kg-m2
Jç>/Jg — 1-66
hç = 30.7 m
hb — 31.7 m
fq = 45 m
Computed frequencies
uq = 1.24 rad/s;
= 2.73 rad/s
Lagrange s method as discussed in Chapter 8 is now used to dérivé the
équations of motion of this monotower. For this two degree of freedom model,
the two équations of motion in the form of équation (8.44) are written in ternis