Influence of fluid structure interaction on a concrete dam during seismic excitation

• The aim of this study is to investigate how fluid-structure interaction (FSI) may be included in numerical earthquake analyses of dams. The basis for this project is Theme A from ICOLD’s 12th International Benchmark Workshop on Numerical Analysis of Dams[5], which was held in October 2013 in Austria. The focus of Theme A was on how to account for fluid-structure interaction in numerical earthquake analyses of dams. In this study, parametric numerical analyses have been performed, where the purpose was to isolate some important parameters and investigate how these influence the results in seismic analyses of dams. These analyses were performed through the use of the finite element method, where the reservoir was modelled with acoustic finite elements. The studied parameters are the choice of Rayleigh damping parameters, reservoir boundaries, and wave absorption in the foundation-reservoir interface. The use of acoustic elements has proven to be a powerful approach for FSI analyses of a dam-reservoir-foundation system. The acoustic finite elements provide reasonable computation time, while allowing for more advanced features such as bottom absorption and non-reflecting boundaries. The choice of Rayleigh damping coefficients has proven to be a challenging task,where it has a significant impact on the results. The method proposed by Spears & Jensen[1] has a physical meaning in the sense that this method excites the same effective mass for the Rayleigh damped case as for the modal damped case. If a constant modal damping is desired, or prescribed in a standard, this method provides a reasonable and sound method to choose the Rayleigh damping parameters for a complex structure. A more straightforward method is to choose the two frequencies in such a way that the span between the frequencies covers about 80% of the effective mass. The choice of reservoir boundary conditions was based on the assumption of an infinite reservoir. A conservative approach is to use a fixed boundary condition, where the pressure waves are reflected at the upstream boundary of the reservoir. However, this parameter proved to be the one that least affected the results in the time-history analysis. The reflection coefficient describing bottom absorption showed to greatly influence the results, and this coefficient should be used  carefully.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Samhällsbyggnadsteknik -- Infrastrukturteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Civil Engineering -- Infrastructure Engineering (hsv//eng)

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