Date of Award

Fall 12-20-2020

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Civil Engineering

Advisor

Kimberly Huguenard

Second Committee Member

Anthony Viselli

Third Committee Member

Lauren Ross

Abstract

Global warming and sea level rise threaten to render traditional coastal protection structures as less effective. Floating breakwaters offer the advantages of adapting to rising sea level, allowing important material transport to occur, and being able to deploy and adapt to varying environmental conditions (seabed, depth, etc.). Traditional floating breakwaters typically consist of reflective concrete structures that are limited semi-sheltered locations. This research aimed to construct floating breakwaters out of lightweight materials with a smaller footprint while utilizing alternative attenuation mechanisms. Three breakwaters consisting of a box, beach, and pipe designs were constructed at 1:40 scale and tested in a Wind and Wave Basin located in the Advanced Structures and Composites Center at the University of Maine. All three were designed to be constructed of lightweight composite sandwich material as opposed to concrete. The pipe breakwater was designed to utilize drag and vortex shedding as wave attenuation mechanisms, while the beach was designed to utilize wave breaking to induce turbulence. The target operation environment for the breakwaters was a period of 3-6 s, and within this range, the beach breakwater was able to attenuate 50% of the energy up to a period of 5.5 s. This was comparable to the box, which attenuated 50% of the energy up to a period of 7.5 s. The beach was able to utilize an alternative to reflection to attenuate wave energy, with greater than 50% of the attenuation coming from dissipation. The beach also had the advantage of being half the full-scale width of the box, 8.56 m wide compared to 16.9 m for the box. The overall weight of the full scale box breakwater constructed from composite sandwich materials was 88% less (200 metric tons vs 1548 metric tons) than the same design made of conventional concrete. This work demonstrates the possibility to reduce the size, weight, and attenuation mechanism of a breakwater, while maintaining its overall effectiveness.

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