Hull Girder Ultimate Strength Research On Longhold Ship

Fewer transverse bulkhead between decks and strong rib or beam is set in the hull structure are the basic features for the longhold ship, such as roll-on ship or amphibious landing ship. As the features in structure, overall instability of deck plate is usually happened in longhold ship. Therefore, It is necessary to take full consideration of the characteristics of the ship hull when the ultimate strength of the ship is evaluated.The Smith method and the nonlinear finite element method are the main methods to calculate the ultimate strength of hull girder at present.However, the overall instability of the deck is not considered in the Smith method.The applicability of this method is need to discuss in the calculation of the ultimate strength of the longhold ship. In view of the above, the main contents of this paper are:(1) Failure mode of stiffened plate is discussed, the calculation method of the critical stress of stiffened plate and the plate grid under some failure modes (including theoretical calculation formula, the standard algorithm and the nonlinear finite element method) are being sorted out. Two typical longhold ship stiffened plate and one typical panel structure are selected as the object of study. The rationality of using nonlinear finite element method to calculate the cabin type of ship hull girder ultimate strength of is verified.(2)Considering the situation of overall instability of deck plate of the longhold ship, limitations of Smith method are discussed during the calculation of the ultimate strength of longhold ship.(3)A typical type of longhold ship deck plate frame is selected as the calculation model, the critical stress - strain curves are obtained by the nonlinear finite element method when the deck plate is unstable. The stress strain curve is considered in the Smith method to get the ultimate bending moment, and the results are compared with the results obtained by the nonlinear finite element method.(4) Considering the operating characteristics of the longhold ship, effect of the deflection of the neutral axis caused by asymmetric section in Smith method are considered in the cabin ship residual load bearing capacity. The calculation program of Smith method is improved. The numerical results are compared with the numerical results obtained by the nonlinear finite element method.