Condensational modelling and experimental analysis for vibration of multilayer hull section

A vibrational modeling approach for the free and forced vibration analysis of multilayer hull section structures with intermediate supports has been introduced, complemented by experimental investigations into the free vibration characteristics of ship hulls. To address the issue of excessively large matrix dimensions in solving large and complex coupled structures, a condensation model is employed to construct the multilayer hull section, and the collocation method is engaged for the coupled solution. To validate the convergence and accuracy of existing methods, comparisons have been made between the natural frequencies, modal shapes, and dynamic responses of the coupled structures with finite element results, and experimental tests have been conducted. The results are found to be effective and accurate, with the modeling process being more straightforward and efficient. Furthermore, the effect of the number of internal decks (layers) and partitioned plates on the structural free vibration characteristics has been studied. It is observed that both the addition of internal decks and the introduction of vertical partitioned plates significantly alter the self-vibration characteristics of the entire hull section, but the first two modal shapes of the hull section remain largely unchanged. Notably, the natural frequency of the hull initially increases and then decreases when internal decks are suddenly added; the low order modes appear on the lower plates not directly connected to the partitioned plates when vertical partitioned plates are suddenly introduced. The method allows for the arbitrary modification of the number and position of decks and partitioned plates, akin to altering material properties. The findings indicate that the presented method can be readily extended to address the vibration issues of hull section structures of arbitrary complex geometries and composite material hull section structures.