Study On Design Of Ultimate Strength Testing Cabin Model

It is a novel idea to set longitudinal box beams on the decks of ship hold sections. So far the study on the ultimate strength is limited in that the limit condition of the collapsing process as well as the collapsing mechanism is not clear. To accurately predict the limit load is another problem. There remain quite a few unexplored problems concerning the ultimate strength of hold sections enhanced by box beams.Model test has been one prevalent method to study the ultimate strength of hold sections. By using the scale model, we can reduce the difficulty and costs of experiments. Through tests, it is easy to observe the progressive collapsing process of the hold structures locally or generally. Due to the existence of multiple nonlinear factors, direct dimensional analysis (realized by similarity theory of mathematics) may lead to unrealistic results. Therefore, model test is carried out to validate the nonlinear finite element simulation as well as the prediction method. The latter is built upon theories of beams and columns of structural mechanics.The contributions of the present study are as follows:(1) This study finds out the design principles and limitations of hold section models. Based on the theories of ultimate strength of hold section structures, the testing model for the ultimate strength of the hold sections reinforced with box beams is also designed. Two schemes for model test design are presented: the model scheme for deck frames with longitudinal box beams and for hold sections.(2) The ultimate strength of the two model designs are predicted by the theories of beams and columns and by nonlinear finite element analysis. These two methods produce quite close results. The prediction for the deck frame model is especially accurate with difference of the two predictions less than 5%.(3) The fundamentals of the similarity theory and dimensional analysis are introduced. It is demonstrated by the example of a hold section model that the model results can be extended to the original models. This can be achieved under the premises that the structural response is within the range of linear elasticity. (4) The structural nonlinear problems and the nonlinear factors in the ultimate strength experiment o f hold sections are classified. The impact of these nonlinear factors on the directional dimensional analysis is investigated. Besides, the causes of the influences of nonlinear factors on the directional dimensional analysis are sought out from three aspects, namely the limitations of the directional dimensional analysis, the features of the limit strength problems and the phenomenon similarity.This thesis initially designs the experimental model for the hold section ultimate strength and lays a foundation for the experiment. Furthermore, application of the similarity theory in the section hold ultimate strength is discussed and revision formulas are regressed which apply to the experiment of hold section models. Although the proposed formulas are still insufficient in some conditions, they offer a way to apply the similarity theory in solving the problems of section hold ultimate strength and serve as reference for future researches.