An Analysis Of Ultimate Strength Of Ship Hull Girders

In the modern ship construction design research realm, people pay more and more attention to the ultimate strength of ship hull girders. This is because that the perfect construction design is closely neted the true strength store of the ship girders.However,in order to understand the actual strength store of ship hull girders,we must have a right assessment of the ultimate strength of ship hull girders.This thesis used along Caldwell's direct calculation method of the ultimate strength of ship hull girders, considered the double bottom and upperwing tank to ship ultimate strength contribution, first defined the stress distribution of the whole section of the ship girders. That is: in the sagging condition, deck and side shell of nearby deck remain the ultimate bucking strength, double bottom remain the yield stress. And the other parts keep elasticity. In the hogging condition, double bottom and the side shell remain the ultimate bucking strength, deck and upperwing tank remain the yield stress, and the other parts keep elasticity.Then the key to calculate the ultimate strength of ship hull girders is to ascertain the ultimate bucking strength of the stiffened panels.In this regard,the developed formulation is designed to be more sophisticated than previous simplified theoretical method for calculating the ultimate strength of stiffened panels under combined in-plane bending and lateral pressure.Fabrication-related initial imperfections(initial deflections and residual stresses)are included in the panel ultimate strength calculation as parameters of influence.All possible collapse modes involed in collapse of stiffened panels,including overall buckling collapse,column or beam-column type collapse,tripping of stiffeners and local bukling of stiffened web are considered.Finally, on base of the above research contents, a program is developed in FORTRAN language by using this simplified method to analyse the ultimate strength of ship hull girders. In comparison with the results from some famous experts of International Ship & Offshore Structures Congress. This simplified method has engineering accuracy and can be used in the pre-phase of design.