Research On Direct Calculation Of Coastal Open Container Ship

The container ship has special structure form and high requirement of torsional strength.The width of its deck opening is same with its cargo hold,and the stress concentration often appears at the hatch corner.Due to the water on deck,open container ships are designed with larger freeboard,and the hull structure weight is generally larger than the non open container ships.With the rapid increase of the freight transport demand,the container ships have to improve its structural design and strength standards.In this thesis,based on the classification rule for steel sea going ships(2018)issued by China Classification Society,a complete set of direct calculation methods for structural strength of coastal open container ships is explored,.Taking a 134.50 m container ship as the research object,the yield strength of this ship is analyzed from three aspects: cabin section,whole ship and local structural strength.According to the strength standard in the rule,the hull structure which does not meet the strength requirements is strengthened by the direct strength analysis(DSA)for the whole ship and the section of container ship.By comparing the load curve and stress distribution of the hull girder in the cargo area of the whole ship and the section model,the rationality and application scope of the whole ship and the section are analyzed.The influence of the DSA method revision on calculation results and structural design of container ships in the current rules is discussed.The detailed grid analysis of the hatch corner is carried out,and the local model is used to explore the arrangement of the mooring and the local strengthening plan of the fastening equipment.At last,the calculation method of buckling strength is studied.Through the above research,the deformation,stress distribution and buckling analysis results of the target ship under the yield strength are obtained,which can comprehensively reflect the actual stress situation of the whole ship and the local part of the ship.The result shows that the new yield strength requirements are more comprehensive and reduce the workload of the DSA.In the DSA of the whole ship,two methods are used to apply the off board water load: selecting trochoidal wave and the wave load calculation result as the equivalent design wave.The calculated stress distribution of the hull structure is consistent except the ship’s bow and stern or near the water line.The direct calculation method of wave load can cover the wave induced load under a variety of wave conditions during the service life,while the application of trochoidal wave to the equivalent design wave load does not require action balance adjustment and is convenient and efficient.Compared with the DSA of the whole ship,the stress distribution of the target ship in the middle of the cargo hold is similar.The cabin model can cover the key areas of the structural design,but the cabin model analysis can be counted a conservative analysis method because of the inaccurate application of the bending moment applied on the front and rear end sections.The load simulation of the whole ship model is more real,covering more comprehensive verification range,and the stress level is closer to the actual situation.The refined model and the local grillage model are used for in-depth analysis to research the local strength problems.Results show that there is little difference between the submodel method and the embedded method at the negative corner of the hatch in the refined core area.However,it is suggested to adopt the submodel method to improve the calculation efficiency.In ship design,fairlead and its reinforcement structure should be reasonably arranged.For the buckling calculation and analysis,the new rule uses HCSR’s buckling calculation method as reference.The new buckling calculation method requires higher standards such as the scope of buckling,the check methods of curved plate and perforated plate,the division of buckling grids.Although the plate division of the new rule refers to the HCSR method,the buckling thinning thickness of the new rule follows the standard thinning thickness of the old rule.There is no obvious regularity in the difference of buckling results between the two versions of the rule.The research work of this thesis provides a reference for the structural design of the new coastal open container ship,and also has a certain reference value for the DSA part of the sea going ships follow the current rules.