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A dynamic analysis of the Okanagan Lake floating bridge

University of British Columbia

This thesis describes a time domain dynamic analysis of a proposed floating bridge on Okanagan Lake in Kelowna, British Columbia, Canada. The analysis begins with wave hindcasting using wind data collected at the bridge site and the nearby towns of Penticton and Kelowna. The influence of lake geometry and bathymetry on the design wave conditions is accounted for through the use of a numerical wave hindcasting model. The results of the wave hindcasting model are compared with wave data collected at the bridge site, and directional wave spectra based on the design wave conditions are then constructed for north and south storms. The next stage of the analysis is the calculation of wave loads on the bridge. A computer model based on two-dimensional linear wave diffraction theory is used to calculate the sectional hydrodynamic coefficients. Force time series are then computed by discretizing the directional wave spectra, and combining the regular wave components with the appropriate wave exciting force coefficients and random phases. Superposition of these forces provides the hydrodynamic forces on the bridge as a function of time. A structural analysis of the bridge based on the finite element method is then conducted for north and south storms. The results of the analysis include sway, heave and roll displacements, bending moments in the pontoons and mooring cable tensions. Additional topics that are investigated include the influence of slowly-varying wave drift forces on the response of the bridge, and the variability in response parameters between simulations. The south storm was found to provide the largest bridge response with maximum bending moments about the z and y axes of the pontoon string of 190,000 and 290,000 kNm respectively, and a maximum cable tension of 1,670 kN. Variability between simulations was found to be considerable, with an average coefficient of variability of 0.096 for all response parameters in 10 simulations. The slowly-varying wave drift force was found to be equivalent to a static wave drift force at the significant wave height.

Thesis/Dissertation

application/pdf

2009-06-26

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http://hdl.handle.net/2429/9738

Civil Engineering

University of British Columbia

UBCV

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