Study On The Residual Strength Assessment Method Of Damaged Hull Girder

The residual strength of ship hull is an important index expressing the safety andreliability of the structure. Reasonable assessment of the damaged ship’s ultimatecarrying capacity to the external load is helpful to carry out hull structure design andreduce accident losses.After studying the floating state and load effect of damaged hull girder, aultimate strength calculation program using Smith’s method based on CommonStructural Rules was complied; The numerical simulation technology of ultimatestrength calculation with Nonlinear Finite Element software Abaqus was studied, anda12,000DWT tanker was took as a study case, its residual strength in condition ofdifferent load condition, different combination of flooding compartment and differentheeling angle were calculated; A ultimate strength experiment of small scale damagedstructures was carried out, the experimental results and calculation results werecompared. Main content and conclusions are as follows:(1) A relatively complete damaged ship’s residual strength assessment processbased on Smith’s method and Nonlinear Finite Element method has been sorted out,which considered the change of floating state and load effect, and took the influenceof initial heeling angle to the damaged hull girder under asymmetric bending intoaccount.(2) The ultimate strength calculation program has simplified the input parametersof hull girder’s cross-section, and realized the automatic division of the element,along with the floating state and load calculation program, can carry out the rapidassessment of damaged hull girder’s residual strength, the example and model testhave verified the program has a certain accuracy.(3) Ultimate strength calculation using Nonlinear Finite Element method withAbaqus was carried out, while numerical simulation technology (including solvingmethod, compartment length, corrosion addition and etc.) was studied firstly, then asolution for ultimate carrying capacity calculation of damaged hull girder wasproposed, and related calculation results of12,000DWT tanker in condition ofdifferent floating state and damage were derived.(4) The ultimate strength experiment of intact and different location of damagedstructure was carried out, experimental results and calculation results matched well, and the influence of different location of damage to deformation mode and ultimatecarrying capacity was evaluated.(5) The floating state of damaged ship will have a great influence to the residualstrength, and the traditional residual strength assessment in upright floating state tendsto come to dangerous conclusions. The residual strength of damaged hull girderdeclines with the increase of heeling angle in general, while in case of big heelingangle, it’s particularly evident, and sagging condition is in a more dangerous situation.Local dent will have impact to ultimate carrying capacity of damaged hull girder,especially in bottom dented condition.(6) The Nonlinear Finite Element method based on systematic numericalsimulation technology can get the accurate ultimate carrying capacity and failuremode of damaged hull girder when carrying out the residual strength assessment. TheSmith’s method has the advantage of faster speed of calculation, but in case of largeheeling angle, the method trend to get a dangerous conclusion.