Random Vibration of Ship Hulls
Measurements of the bending moment induced stresses in a ship hull when the ship is moving in a sea-way, have revealed a marked asymmetry, cf. Juncher Jensen and Terndrup Pedersen (1979,1981). It has been observed that the longitudinal peak stresses in the bottom plates of the hull are generally larger in tension (sagging) than in compression (hogging). This phenomenon will not be captured by a linear theory of wave forces and response. To have available a practical prediction tool it is therefore necessary to set up a nonlinear theory for these vibration responses. This work was initiated by Juncher Jensen and Terndrup Pedersen (1979, 1981), who developed a quadratic strip theory which makes it possible to calculate the vertical vibration response of the ship hull taking due account up to second order of nonlinearities in the exciting waves, the nonvertical ship sides and nonlinear hydrodynamic forces. The flexibilty of the ship is also taken into account by modelling the ship hull as a nonprismatic Timoshenko beam with variable mass and stiffness.
KeywordsProbability Density Function Vibration Response Ship Hull Quadratic Response Saddle Point Method
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