Research On Nonlinear Dynamic Response And Buckling Of Stiffened Plates Under Impact Loading

Stiffened plates have wide applications in aerospace, bridge, ship and some other engineering activities due to their economic and structural benefits. Stiffening a plate can achieve higher strength/weight ratio of the structure compared to a bare plate having same material. On the other hand, the discontinuity and inhomogeneity of stiffened structures make the behaviour analysis of them very complex. Study on the dynamic response, and especially the nonlinear dynamic response of stiffened plates is very insufficient. As for the dynamic buckling, many problems need to be studied and perfected for common plate or shell structures, and the open literatures about dynamic buckling analysis of stiffened plates under impact loading are less.The nonlinear dynamic response and dynamic buckling of stiffened plates under impact loading are studied theoretically in the thesis. It is one important aspect of the work that studying the dynamic behaviour of stiffened plates under impact loading, discussing the dynamic response character and mechanism of stiffened plates, and considering the influence of discontinuity and inhomogeneity due to stiffeners on the global dynamic behaviour of structures by reasonable theoretical models and effective numerical methods. The main content and achievements of this thesis are as follows:1. Using elastic constraint boundary condition in which is accordance with actual ships, the calculation formulae are derived for the nonlinear dynamic response and dynamic buckling of stiffened plates under impact loading, and the factors influencing the dynamic response and dynamic buckling are analyzed in detail. The results of analyzing the influence of boundary condition can provide theoretical basis for the design and calculation of actual ship grillages.2. Based on plastic theory and considering the influence of axial force, the bending moment-axial force interaction relation (generalized yield condition) for singly symmetric cross sections is derived. The theoretical formulae have important practicality in dynamic plastic analysis of structures. 3. The dynamic plastic response of one-way (or two-way) stiffened plates with large deformation is theoretically investigated for a singly symmetric beam model (or intersecting beams with singly symmetric cross sections). The theoretical results of this method are contrasted with those of some other methods.4. The simplified method is presented that an arbitrary impact load can be replaced equivalently by a rectangular pulse. Many calculations are preformed to confirm the validity of equivalent substitution. For plastic deformation structures, the equivalent substitution method of arbitrary impact loads can be used to simplify the calculation if the final plastic deformation needs to be known.5. The instantanuous mode solutions are obtained by Lee's extremum principle when the dynamic rigid-plastic response of two-way stiffened plates with large deformation is calculated. The instantanuous mode solution by Lee's extremum principle is a simple and practical approximate method for studying dynamic plastic response of structures with large deformation, which is proved by the analysis of examples.Through the comparisons among the results from many examples, it verifies that the adopted methods are correct, the developed programs are effective and the obtained results are accurate.