Author Archilla, Juan Carlos
URN etd-040799-050250
Title Three-Dimensional Nonlinear Dynamics of a Moored Cylinder to be Used as a Breakwater
Degree Master of Science
Department Civil Engineering
Advisory Committee
Advisor Name Title
Raymond H. Plaut Committee Chair
Richard M. Barker Committee Member
Siegfried M. Holzer Committee Member
Keywords
* mooring
* breakwater
* vibration
* cylinder
* snap load
* nonlinear dynamics
* chaos
Date of Defense 1999-04-05
Availability unrestricted
Abstract
A three-dimensional, nonlinear dynamic analysis
is conducted on a fully submerged, rigid, solid
cylinder to be used as a breakwater. The breakwater
could potentially be used as a single cylinder to
protect small structures. Alternatively, multiple
cylinders could be positioned in series to protect
shorelines, harbors, or moored vessels from
destructive incident water waves. The cylinder is
positioned with its axis horizontal and is moored to
the seafloor with four symmetrically placed massless
mooring lines connected at the ends of the cylinder.
The mooring lines are modeled as both linearly elastic
("regular") springs and compressionless springs.
All six degrees of freedom of the structure are
considered. The breakwater is modeled in air with a
net buoyant force acting through the cylinder's center
of gravity. The six "dry" natural frequencies of the
structure are computed. Both linear and nonlinear free
vibrations of the structure are considered. Linear
damping is used to model the fluid and mooring damping
effects. Normal and oblique harmonic wave forces at
various frequencies and amplitudes are applied to the
cylinder. The effects of the forcing amplitude and
frequency, and the coefficient of damping, on the motion
of the breakwater are studied. The results show that
more erratic behavior occurs for the breakwater with
compressionless springs, mainly due to the development
of snap loads in the mooring lines.
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