Author Farmer, Anthony Lee
Author's Email Address afarmer@vt.edu
URN etd-112999-093701
Title INVESTIGATION INTO SNAP LOADING OF CABLES USED IN MOORED BREAKWATERS
Degree Master of Science
Department Civil Engineering
Advisory Committee
Advisor Name Title
Raymond H. Plaut Committee Chair
Kamal B. Rojiani Committee Member
Siegfried M. Holzer Committee Member
Keywords
* nonlinear dynamics
* vibration
* snap loading
* breakwater
* mooring lines
Date of Defense 1999-11-18
Availability unrestricted
Abstract
A two-dimensional, nonlinear dynamic analysis is conducted on a moored breakwater
configuration to investigate snap loads in mooring lines. Breakwaters are structures used
to attenuate or eliminate waves and protect shorelines, harbors, and other natural and
man-made marine structures from wave damage. The breakwater in this investigation is
modeled both as a point mass and as a rigid body. Both models are subjected to free
undamped motions and forced undamped wave motion. Energy is dissipated through the
use of a coefficient of restitution applied when a mooring line becomes taut (i.e., reaches
its natural length). The mooring line is modeled as an inextensible cable with no axial or
bending resistance when slack. Snap loading arises when a mooring line transitions
suddenly from a slack condition to a taut condition. The analysis was conducted on a
breakwater configured upside down and hanging by two mooring lines. The length of the
mooring lines, coefficient of restitution, size and shape of the breakwater, initial position
of the breakwater, amplitude of wave forcing, ratio of vertical to horizontal forcing, and
frequency of forcing were all varied in the analysis. The results show that the rotations of
the rigid body and the wave forcing have a significant role in the analysis, indicating that
a rigid-body model for a moored breakwater under wave forcing is the more accurate model.
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