| With the rapid development of shipment industry, multi-functional andlarge-scale ship structures are currently demanded in the field of ocean market. Whenship is running in the sea, the safety and reliability of ship structures are of highimportance besides high operational performance. Until now, both international anddomestic scholars have done many researches on the area, contributing muchachievement into this field. In fact, in terms of checking ultimate strength about ship,many applicable and simple calculation methods have been proposed, whoseaccuracy can meet the need of safety while shipping. However, although there aremany accurate ways for us to assess the ultimate strength of ship structures, thevalues that are gained from these methods are all based on one-time collapse. But thetruth is that the ship is subjected to repeated loads while sailing in the sea. When thisstructure is confronted with sea wave, the ultimate strength of ship will not stay still.It is dangerous to consider the ultimate strength resulting from one-time collapsealone. Thus, in order to elevate the safety of ship structures, related researched intoultimate strength from cyclic loading is in need. Currently, cyclic collapse of shipgirder has arisen the attention of many scholars; the methods they use to do theanalysis include theoretical analysis, finite element method and experiments.However, current researches mostly focus on the ultimate strength of ship girderunder axial cyclic loading, ignoring the situation of mixed loading patterns. In fact,when ship is sailing in the sea, it is confronted with still water loading besidessagging and hogging, which may affect its bearing capacity.Ship structure is a combination of beams and plates with stiffened panels as itmain bearing members. Analysis about the accumulatively plastic collapse of shipgirder can begin from the stress-strain relationship of plates and stiffened panels. Inthis paper, the plates and stiffener-panel selected from ship bottom are chosen. Theloading condition is selected from the real loading situation when ship is in the sea.The method that used to analyze the ultimate strength of ship structures is finiteelement method. The main task of this paper is to analyze the ultimate bearing performance ofplates and stiffener-panels under the combination of axial cyclic loads and lateraluniform pressure, using finite element method to find the factors that affect thebearing performance and deformation properties of those two models. The mainworks done in this paper are as follows.（1）The stress-strain relationships of plates under axial load and lateral pressureby numerical method are calculated. Comparing the result with that of relative papersto make sure that the method used in this paper is reasonable.（2）The ultimate strength of two plates under cyclic loading using numericalmethod is analyzed. At the same time, two different scales of tensional load and threedifferent water pressures are applied on structures to gain their effect on the bearingperformance of ship structure.（3）Different levels of lateral pressure analyzing the ultimate strength ofstiffener-panels are applied on structures. Two kinds of models are selected, one isstrong, and the other is weak. At the same time, three different scales of tensions areapplied, such as still amplitude, slowly mounting amplitude, faster mountingamplitude.（4）According to the application of shipyard, three different kinds of stiffeners,say flat steel, angle steel and T-shape steel, are used to build the ship. Thus, this paperalso analyzes the effect of different types of stiffeners to the ultimate strength resultedfrom cyclic loading. |
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