Modification of boundary condition for the optimization of natural frequencies of plate structures with fluid loading

A finite element method, boundary element method, and genetic algorithm combined method is developed for the optimization of natural frequencies of fluid-loaded plates. In this method, the coupled finite element method–boundary element method is used for the free flexural vibration analysis of plates with arbitrary fluid loading effects and arbitrary elastic boundary conditions, and the genetic algorithm method is combined with the finite element method–boundary element method for searching the optimal values of plate’s boundary parameters. By using this method, multiple natural frequencies of a given fluid-loaded plate can be optimized simultaneously to different target values. The coupled finite element method–boundary element method is first validated by comparing with earlier published results. The proposed optimization method is then applied to the optimal boundary condition design of four different cases. The results show natural frequencies of a fluid-loaded plate are sensitive to its boundary conditions. The possibility of optimizing the natural frequencies of a fluid-loaded plate by modifying boundary conditions is demonstrated, as well as the effectiveness of the proposed method as a structural optimization tool. According to the authors’ knowledge, this study is the first attempt of optimizing fluid-loaded plate natural frequencies by considering arbitrary boundary conditions as optimization variables.

Ground base deformation by circular plate peculiarities

It is established that at the moment of the onset of the boundary equilibrium of the base under a central loaded plate, an elastic core is formed in the form of a cone, all particles move along with the plate progressively down. In this case, within the limits of the “area of influence” the boundary condition of the base is violated by protrusion or consolidation of soils. The volume of the “area of influence” is determined by the height of the elastic core, from which its diameter is calculated. Experiments using conical tips were made and the height of the elastic core was determined and the diameter of the “area of influence” was determined. For creation at penetration and probing friction of soil on a ground the conic tip is executed rough with cylindrical stages. Under the steps of the tip, formed areas of compacted soil, moving along with it, creating a so-called “ground shirt” in the form of a cone with a creature at an angle α to the vertical. The obtained data allowed specifying coefficients of bearing capacity of soils, which are used in construction norms.