Expanding Research On Smith Method For Calculating Ultimate Strength Of Ship Hull Girder

The hull girder ultimate strength is one of the important indexes to ensure the safety of ships.Smith method is a regular simplified method based on several fundamental assumptions for calculation of the hull girder ultimate strength.However,with the development of the large type,light type and diversity of ships,the multi-span deck grillage with beams below the critical stiffness has become more and more common,and the influence of lateral pressure is taken more and more serious.The situations above all exceed the assumed sphere,thus Smith method need to be improved.This paper analyzes the multi-span instability of grillage and lateral load effect by adopting theoretical method.And the research can help to expand the application range of Smith method,make ship design more reasonable and economic and has important theoretical and practical value.The main content is as follows:(1)This paper deduces the load-end shortening curve formula of the stiffener unit of a multi-span instability stiffened plate,thus the influence of multi-span instability can be considered.(2)This paper deduces the load-end shortening curve formula of the stiffener unit of a multi-span instability stiffened plate under the action of lateral load,thus Smith method can be applied in the actual situation with lateral pressure.(3)Based on the calculation and analysis of multi-span buckling and lateral pressure factors,the effects of various parameters are found.(4)Program the correction formulas into the calculation software of Smith method,and calculate the ultimate strength of several sections.(5)The NFEM is adopted to verify and calculate the model and verify the rationality of theoretical correction method.