MATHEMATIC MODEL OF A BEAM PARTIALLY SUPPORTED ON ELASTIC FOUNDATION

The paper presents the methodic for analytical determining of stress-strain state of a beam partially supported on elastic foundation at sudden damage of foundation structure (partial failure). Bending equation for a beam is written using dimensional parameter and solved with the initial parameters method. Such approach al­lows to obtain dimensional analytical solution to static and dynamic problems for universal boundary conditions of a beam since it always leads to equations’ system of second order. Using numerical analysis for various values of generalized stiffness parameter of a system “beam - foundation”, we established affecting of the length of failure foundation part to stress-strain state of the beam for two supporting variants: partial supporting and sup­porting by two ends with foundation failure in the middle part of the beam.

THE REACTIONS OF THE «BEAM – FOUNDATION» SYSTEM TO THE SUDDEN CHANGE OF THE BOUNDARY CONDITIONS

The authors constructed a mathematical model of a dynamic process in a loaded beam on the elastic Winkler foundation in a sudden formation of a defect in the form of a change in the boundary conditions. The solution of the static problem of bending of the beam pinched at the ends served as the initial condition for the process of forced vibrations hinged supported at the ends of a beam, which arose after a sudden break in the connections that prevented the rotation of the end sections. The authors determined the dynamic increments of stresses in a beam for various combinations of a beam and foundation parameters.

Study of the bending vibration characteristic of phononic crystals beam-foundation structures by Timoshenko beam theory

Vibration problems wildly exist in beam-foundation structures. In this paper, finite periodic composites inspired by the concept of ideal phononic crystals (PCs), as well as Timoshenko beam theory (TBT), are proposed to the beam anchored on Winkler foundation. The bending vibration band structure of the PCs Timoshenko beam-foundation structure is derived from the modified transfer matrix method (MTMM) and Bloch's theorem. Then, the frequency response of the finite periodic composite Timoshenko beam-foundation structure by the finite element method (FEM) is performed to verify the above theoretical deduction. Study shows that the Timoshenko beam-foundation structure with periodic composites has wider attenuation zones compared with homogeneous ones. It is concluded that TBT is more available than Euler beam theory (EBT) in the study of the bending vibration characteristic of PCs beam-foundation structures with different length-to-height ratios.