Mooring Loads Due to Parallel Passing Ships - State Lands ...

With the above coefficients, peak loads may be predicted from equation (1) as:
1 2
FX− = ρ DLV C
2
X−
1 2
FY+ = ρ DLV C
2
Y+
1 2 2
M− = ρ DL V C
2
M −
As illustrated in Figure 14, these are the peak loads, in the positive direction for
FY, and in the negative direction for FX and M. The secondary maxima in the opposite
direction can be estimated as
FX+ = 085 . FX−
FY− = 061 . FY+
M+ = 091 . M−
These are based on the average relationship between the positive and negative
force maxima from the lab tests. As illustrated in Figure 12, the theoretical results of
Wang suggest that FX and M should be larger than indicated with the same magnitude
in the positive and negative direction, while the negative sway force should be a little
smaller than indicated or about 0.46 FY+.
Peak loads predicted using equations (2) and (3) have been compared to
measured coefficients from Table 5, with results plotted in Figure 18. In each part of
the figure, measured and predicted loads are compared to a line of perfect agreement.
While the empirical model is developed to give no bias toward over or under predicting
the peak loads, some scatter is apparent. This is due to inherent variability in the
experiments and due to the simplified nature of the empirical model. Maximum error is
on the order of ± 25% with typical error on the order of ± 10%. Scatter is largest for the
surge force, as this is the smallest load and most difficult to resolve in the
measurements.
NFESC TR-6056-OCN
24
(3)
(4)