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14 Tides and Waves on Vegetated Coasts
A
c
x
Fig. 14.12: Scheme of the Y-shape coral branches
Moments given by Eqs. (14.28) and (14.31) try to turn branches (A - B) and
(B - C) around the point B in clockwise direction, considered as a positive.
Other forces imposed on coral branches are forces due to gravity. Assuming
that coral density is uniform along the whole branch, the gravity force at branch
(A - B) produces the following moment at the point B:
(14.32)
in which Pc is the coral density.
The sign (-) in Eq. (14.32) indicates that the moment M1 A - B ),grav is negative,
i.e. gravity force moment tries to turn branch (A - B) around the point B in
the counterclockwise direction. In a similar way we can determine the moment
M (B-C),grav .
B
as.
(14.33)
The total moment at the point B is the summation of all moments acting on
branches (A - B) and (B - C), i.e.:
Another critical cross-section of Y-shape coral branch is the cross-sectional
point 0, at the substratum. Moment at the point 0 includes the contribution