In most ships and offshore structures, plates and stiffeners are welded together. These structures inevitably vibrate during operation under dynamic loads by the main engine, working machinery, waves, propellers, etc. Especially, resonance causes a sudden increase in the amplitude of vibrations of the structural components of ships. As a result, it may cause a tremendous hindrance to the ship’s normal operation, causing damage to the ships and great suffering to the crew’s work and living conditions. Therefore, designing the stiffened plate structure with a correct consideration of their dynamic behavior is of great significance in solving the partial stiffness and local vibration problems of the ship structure.
Intermittent welding is generally used to attach stiffeners to plate for reducing manufacturing costs and for decreasing the weight of structures and welding distortion. Intermittently welded structures are widely used in practice, but few analytical studies have been carried out on the behavior of intermittently welded stiffened plates. The only focus has been on the static analysis of the ultimate strength and collapse behavior of the intermittently welded structures and vibration problems have been rarely discussed.
Ri Yong Ho, an institute head at the Faculty of Shipbuilding and Ocean Engineering, has proposed a simplified method for analyzing the dynamic behavior of intermittently welded stiffened plates.
First, he assumed the plate and stiffener as individual beams and considered the influence of the longitudinal internal shear force per unit length at the stiffener-to-plate junction of a continuously welded stiffened plate. Then, he divided the whole span of an intermittently welded stiffened plate into welded and non-welded segments. After that, he changed the intermittently welded stiffened plate into an equivalent continuously welded one, and built a model for bending vibration analysis of the intermittently welded stiffened plate. On this basis, he formulated a governing equation for bending vibration analysis of the intermittently welded stiffened plate by the influence function method and newly developed a practical approach to solve the governing equation. He verified the validity of the proposed method by comparing it with the finite element analysis results.
If further information is needed, please refer to his paper “A study for the bending vibration analysis of the intermittently welded stiffened plate” in “Marine Structures” (SCI).
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