Author(s): Woosuk Ahn; Robert F. Henry; Vladimir Shepsis; C. J. Garrison
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Keywords: No Keywords
Abstract: A large, 439 m (1,440 ft) long, 7.5 m (24.5 ft) wide, and 3.1 m (10 ft) deep, floating concrete wave attenuator has been constructed to expand the Port of Bremerton's marina in downtown Bremerton on Puget Sound in Washington State, US. The wave attenuator was designed to protect the marina from wind-driven waves and ferry wakes. An engineering challenge was the effective attenuation of longperiod wakes created by mainly Washington State Ferry vessels bypassing the wave attenuator at various speeds and distances. An optimum geometrical shape of the attenuator was determined by carrying out field data collections, numerical analyses, and physical model tests. The design of the mooring system for the large-size floating structure represented a significant challenge in view of the constraints imposed by water depth, tidal variation, and limited available mooring line scope within the urban waterway site. A hydrodynamic/dynamic analysis of the structure was based on a numerical modeling of wave refraction/diffraction/transmission, using a state-of-the-art HWAVE model and nonlinear, time-domain analysis using the MORA suite of hydrodynamic/dynamic programs. This unique multi-body, timedomain analysis included the approximate effect of the elastic compliance of the extremely long “rigid” structure by breaking it into segments and placing elastic connections based on linear springs between segments to approximate overall structural elasticity. This provided approximate elastic compliance of the structure in bending and torsion, and a method for evaluating the structural loads at the connections. Additional challenges included the durable structural design of the posttensioned wave attenuator, rigidly connected with 12 individual floating bodies and in-water body connections. Use of lightweight concrete and corrosion-resistant highstrength reinforcement significantly contributed to structural durability. This multifunctional state-of-the-art floating structure was designed, built, installed and commissioned in May, 2008. The structure currently serves as both a wave attenuator and a public waterfront park.
Year: 2009