Study On Ultimate Strength Performace Of Warship With New Type Of Deck Structure

Warship's vitality could be divided into two aspects. One is called"before"vitality and the other is called"after"vitality. With rapid development of modern weapons, warships will inevitably encounter the threat of attack from anti-warship weapons. And, the"after"vitality has been more and more concerned by navies. Among plenty of factors in the"after"vitality, longitudinal strength under damage conditions is of significant importance because it is the foundation of warship's survival. To enhance the"after"vitality of warships, study on new type of structures has become a hotspot in navies'work.Box-girders design has been successfully used on Germany"Sachsen"frigate's strength deck. Taking the idea of ultimate state design, this thesis studies the ultimate strength performance of this new structure on"Sachsen". The main point of this thesis is to compare the residual strength performance under typical damage conditions between the new structure and the original one.To simulate the typical damage conditions, the damage effects of modern anti-warship weapon are summarized from history record and two typical damage models are set. One is local break damage model and the other is large deformation damage model. For the former one, the criterion of determining the"failure area"is used and the elements within the failure area are deleted. To complete a comprehensive analysis, many combinations of size and location of failure area are used. For the latter one, a dynamic response analysis is executed to gain the large deformation damage condition and the impact load refers to the characteristic of blast.When study the residual strength, the concept of residual ultimate strength is defined and the nonlinear FEM for calculating the ultimate strength is discussed. To study the process from building the damage model to calculating the residual ultimate strength, a simple practice on a small model is applied, which sets up a foundation for real ship analysis.When the preparations work has been done, a study on a real ship is applied. Taking the idea of"Sachsen", a preliminary design of three box-girders on a general warship's strength deck is done. The size of box-girder is determined mainly according to the general arrangement plan and the buckling performance is also checked using thin-wall structure mechanics theory. Then, the ultimate strength performance is compared between the new structure and the original one, which includes three parts: initial ultimate strength, residual ultimate strength under local break damage conditions and residual ultimate strength under large deformation damage conditions.The result shows that, the new structure has much better ultimate strength performance compared with the original one. The contribution of box-girders is also studied. The work of this thesis provides a valuable reference for independent design and study of the new structure on warship.