Offshore structures of large horizontal dimensions such as gravity platforms and storage tanks have been extensively used. The coupled vibration problem of these structures in seismic regions has been a significant subject of research theoretically and practically. An analytical method is developed to solve the coupled vibration problem of an elastic vertical circular cylindrical structure founded on homogeneous elastic soil with surrounding fluid. An improved mathematical model is adopted so that not only the structure-fluid interaction but also the influence of elasticity of soil are considered. The frequency dependent radiation added mass and hydrodynamic radiation damping are expressed in closed form, and are compared with the generalized mass and damping respectively.
Offshore structures of large horizontal dimensions such as gravity platforms and storage tanks have been extensively used. The coupled vibration problem of these structures in seismic regions has been a significant subject of research theoretically and practically. An semi-analytical method was treated in detail for scattering problems of some fixed and floating cylindrical rigid structures by Mei 1966. By this method, solutions for radiation problem of a submerged rigid cylinder fixed on rigid foundation due to harmonic and arbitrary horizontal seabed motion were obtained by Tung 1979, Bi et al. 1983, and Wang et al. 1985, 1989. Radiation problems of flexible cylinder with rigid foundation or rigid cylinder with elastic foundation surrounded by water were investigated by Liaw et al. 1974, Taylor et al. 1982, and Tanaka et al. 1986. Using different analytical methods and placing emphasis on different points, they showed the characteristics of natural frequency, radiation added mass and hydrodynamic radiation damping, made clear the influences of free surface wave and compressibility of water upon hydrodynamic loading and structural response, and explained the relations between exciting frequency and hydrodynaimc force as well as structural response.
