Research On Sturctural Collapse Behavior Of Flat-type River-sea-going Ship Under Combined Loads

Ship transportation has always been the main status of cargo transportation.Compared with the traditional mode of transportation,river-sea-going transportation has the advantages of low cost and high efficiency.Since the Yangtze River is a natural channel,the length and draught of the ship sailing in it are limited.In the market demand for large-scale ships,the river-sea-going ship is often designed as a flat-type ship with large deck openings.This will reduce the longitudinal strength and torsional strength of the ship.Therefore,the research of the ultimate strength of flat-type river-sea-going ship under combined loads is helpful to improve structural safety and reliability,and also provide technical support for the design of reasonable,reliable and lightweight ship structure.In this paper,theoretical analysis,numerical calculation and model test are combined to investigate the collapse characteristics of flat-type river-sea-going ship with large opening under combined loads.Firstly,the influence of loading path on the ultimate strength of hull structure is discussed,which makes preparations for the formulation of test loading scheme.Then,the hull structure collapse test under the combined load is carried out.By applying two pairs of different loads,a certain proportion of bending and torsion moment are simulated.As the load increases,the test model collapse progressively,and the collapse characteristics of model under combined load are obtained.The following work is finished in this paper:(1)The nonlinear finite element method is used to investigate the collapse characteristics of flat-type hull structure under combined loads.The collapse characteristics of hull structures under pure bending,pure torsion and combined different bending and torsion moment ratio are obtained,and the influence of loading path on ultimate strength is investigated.(2)The nonlinear finite element method is used to investigate the collapse characteristics of the flat-type river-sea-going ship structure under combined loads of the rule design.With the increase of the load,the bottom plate near the bilge of the ship firstly buckles and extends to the middle,the longitudinals of bottom also buckle.As the load increase further,the bottom structure of the ship yields,and then the bearing capacity loses and structural collapse occurs.(3)The collapse test of the flat-type hull structure model under the combined loads is carried out.By applying two pairs of different loads to simulate combined loads proportion of the standard design,the structural response and collapse mode of the flat-type hull structure model are obtained.The structural collapse process revealed by the model test is consistent with the collapse process of nonlinear finite element calculation,but the ultimate bending and torsion moment obtained by the model test are about 15% smaller than the calculated value because of the failure to consider the initial deformation and welding residual stress in the nonlinear finite element calculation.In this paper,the collapse characteristics of flat-type river-sea-going ship under combined loads are investigated,and the ultimate bearing capacity of the structure is obtained,which is of great significance for the design of safe and reliable hull structure.