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Structural Engineering and Mechanics Volume 63, Number 1, July10 2017 , pages 37-46 DOI: https://doi.org/10.12989/sem.2017.63.1.037 |
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Numerical study on the resonance response of spar-type floating platform in 2-D surface wave |
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Eung-Young Choi, Jin-Rae Cho and Weui-Bong Jeong
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| Abstract | ||
| This paper is concerned with the numerical study on the resonance response of a rigid spar-type floating platform in coupled heave and pitch motion. Spar-type floating platforms, widely used for supporting the offshore structures, offer an economic advantage but those exhibit the dynamically high sensitivity to external excitations due to their shape at the same time. Hence, the investigation of their dynamic responses, particularly at resonance, is prerequisite for the design of spar-type floating platforms which secure the dynamic stability. Spar-type floating platform in 2-D surface wave is assumed to be a rigid body having 2-DOFs, and its coupled dynamic equations are analytically derived using the geometric and kinematic relations. The motion-variance of the metacentric height and the moment of inertia of floating platform are taken into consideration, and the hydrodynamic interaction between the wave and platform motions is reflected into the hydrodynamic force and moment and the frequency-dependent added masses. The coupled nonlinear equations governing the heave and pitch motions are solved by the RK4 method, and the frequency responses are obtained by the digital Fourier transform. Through the numerical experiments to the wave frequency, the resonance responses and the coupling in resonance between heave and pitch motions are investigated in time and frequency domains. | ||
| Key Words | ||
| spar-type floating platform; 2-D surface wave; heave and pitch motions; coupled nonlinear equations; coupling in resonance | ||
| Address | ||
| Eung-Young Choi: KFX Airframe Analysis Team, Korea Aerospace Industries, Sacheon 52529, Republic of Korea Jin-Rae Cho: 2Department of Naval Architecture and Ocean Engineering, Hongik University, Sejong 339-701, Republic of Korea Weui-Bong Jeong: School of Mechanical Engineering, Pusan National University, Busan 609-735, Republic of Korea | ||