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Showing 2 results for Shabakhty
M. Shakarami, A. Shanehsazzadeh, N. Shabakhty,
Volume 20, Issue 1 (January 2020)
Abstract
The New Wave theory has recently applied for predicting wave forces on marine structures including offshore wind turbines. However, the validation of the theory in determining wave force has not been fully confirmed. However, the validation of the results for predicting stability parameters of marine structures is necessary. In the present article the prediction of the New wave theory of water surface profile, wave kinematics and offshore wind turbine monopile pier responses to the wave, including base shear, overturning moment and maximum displacement are compared to the experimental data and results from linear irregular wave time series generated from the wave spectrum. The comparisons show that the results are promising and in an acceptable level of accuracy for design purposes. Since the New wave theory takes very short time of processing in compare to real irregular time series, the theory is considered as the reliable substitute for prediction of wave forces on offshore wind turbines. The comparison with the results of the conventional 5th Stokes regular waves shows that the new wave theory is significantly more accurate in predicting wave kinematics and wave loads on offshore wind turbine monopiles.
M.h. Enferadi, M.r. Ghasemi, N. Shabakhty,
Volume 20, Issue 1 (January 2020)
Abstract
Service life and safety of a steel jacket platform is influenced by vibrations generated by environmental loads, waves and winds. Vibrations of the structure and deck may cause fatigue in the structural elements and joints. Also may disrupt the operation of the drilling equipment and facilities as well as the operation of the platform. Therefore, the main aim of this research is to control the vibrations of the steel jacket platform through shape memory alloys dampers. Shape memory alloys have two important properties of shape memory as well as superelastic behavior and are quite suitable for damping applications. In these alloys, crystal structures transition from the austenite to the martensite phase, and vice versa are accompanied by the energy dissipation. In this research, a 90m steel jacket structure equipped with SMA dampers installed in 80m water depth has been modeled as a multi-degree-of-freedom system and analyzed under the time history of wave loads. For solving the differential equations of system vibration and modeling the hysteresis behavior of the shape memory alloys elements, the direct integration alpha method and multi-linear idealized constitutive model have been used, respectively. Jacket platform equipped with the shape memory alloys dampers shows the better result with 42% reduction in deck displacement, 62% reduction in deck acceleration and 32% reduction in shear force of platform base.
