Analysis On Incremental Plastic Collapse Behavior Of Ship Hull Girder Under Cyclic Loading

The ultimate strength study on ship hull girder has attracted great attention whenit was written into the common structural rules of bulk carriers and oil tankers in2006.Nowadays, the popular methods for assessment of the ship hull girder ultimatestrength are based on the static ultimate strength criterion, namely the overall damageof ship hull girder is the result of one-time extreme external moment. But in fact, thereal situation is that ships are always suffering the sagging and hogging bendingmoment when sailing in waves, and parts of the longitudinal bearing member of shiphull structure have different degrees of plastic deformation before one-time damage.With the continuous accumulation plastic deformation, the overall damage willhappen when the ship hull is under a bending moment which is even less than theone-time extreme bending moment, so the thesis about the ultimate strength of shiphull girder based on incremental plastic collapse under cyclic loading has been raised.Few scholars at home and abroad have researched the ultimate strength of ship hullgirder under cyclic loading. Based on the conventional method for calculating theultimate strength of ship hull girder, a method for calculating the ultimate strength ofship hull girder under cyclic loading is presented in this paper, and the hystereticcurve of ship hull girder is got. The work is a breakthrough in the field of the researchon the incremental plastic collapse behavior of the ship hull, which has a certainguiding significance to the prediction of the ultimate strength and the research ofcollapse behavior for the ship hull.In this paper, based on the stress-strain relationship of stiffened plate undermonotonic load, the stress-strain relationship of stiffened plate under cyclic loading isgot and it is used to calculate the ship hull girder ultimate strength under cyclicloading. The main research work is as follows:(1)The collapse behavior of stiffened plate under monotonic load is researched,based on the Rahman’s stress-strain relationship, and combined with the finiteelement method, and finally the stiffened plate stress-strain relationship whichrequired in this paper is got. (2) The hysteretic behavior of stiffened plate under cyclic loading is researched,and the stress-strain relationship of stiffened plate under cyclic loading are concludedas the stress-strain relationship of stiffened plate under different residual strain. Andbased on the stress-strain relationship of stiffened plate under monotonic load, finallythe stress-strain relationship curve of stiffened plate under cyclic loading is got.(3)The calculation method of ship hull girder ultimate strength under cyclicloading has been researched, based on the traditional progressive collapse method, thestress-strain relationship after circulation was used to replace the initial stress-strainrelationship of stiffened plate, and the computer program is written, the calculation ofship hull girder ultimate strength under cyclic loading are obtained.(4) The incremental plastic collapse behavior of stiffened plate under cyclicloading has been studied in detail in this paper based on a real ship. At first, thereliability of calculation method in this paper is verified by contrast, and then the shiphull girder ultimate strength under different cyclic loading process are studied indetail, and the collapse behavior of ship hull girder under cyclic loading are analyzed.