Research On Nonlinear Similarity Criterion For Model Test Of Ultimate Strength

In recent years,ship wreck caused by structural failure is still increasing,resulting in the loss of human lives,property damage which is hard to estimate.Besides that,ship wreck(especially oil tankers,chemical tankers et al)may also cause natural unbearable environmental pollution and ecological damage.The ultimate strength characterizes the most realistic structural bearing capacity.There are many methods for calculating the ultimate strength.For a new ship type or the new type of structure,model test is the most fundamental and effective method to reveal its ultimate bearing capacity.Model test method is widely used in the study of the ultimate strength of hull structure.To predict the ship ultimate strength by model collapse test,similarity between prototype(original ship)and test model must be ensured at first.The existing similarity theory is based on the assumption of linear elasticity,which can only guarantee the similarity in the linear stage.So,the experiment result can only be used to explore the failure mechanism at present.The main work in the present paper is as follows:1)Based on the classical theory of beam and torsion theory of thin-walled structures,the structural response characteristics of hull girder under uniaxial compression load and torsion are analyzed.By reference to the distortional the similarity theory,the similarity criterion is deduced to ensure at the elastic stage.2)According to the successive collapse characteristics of hull girders under longitudinal bending moment,the nonlinear similarity criterion is proposed based on the fundamental parameters which play an important role on ultimate strength.3)The successive collapse characteristics of hull girder under torsion moment are investigated,and the buckling characteristics of plate and stiffened plate under shear load are analyzed.Nonlinear similarity criterion under shear load is proposed based on the fundamental parameters which are of great importance to ultimate strength.The proposed non-linear similarity theory makes up the deficiency of the present similarity theory.It can promote the development of model test technology.Model designed by the similarity will be similar to the original ship,so we can use model experiment result to estimate the ultimate strength precisely.