The methods and algorithm to assess dynamic characteristics of high-rise structures are given in the paper taking into account the variability of slopes and the structure thickness in the framework of one-dimensional theory of viscoelasticity. The Boltzmann-Volterra hereditary theory was used to describe dissipative processes in the structure material. The reliability of results was verified by comparing the obtained results with the exact solution of a number of test problems. Natural vibrations of high-rise chimney stacks and ventilation pipes of thermoelectric and nuclear power plants have been investigated. It was revealed that the natural frequencies of the considered structures fall into the dangerous range of earthquake frequencies. The obtained frequencies of natural vibrations of real structures are compared with the results of field experiments.
The paper is devoted to the study of dissipative properties of inhomogeneous viscoelastic systems of structures with dynamic vibration dampers. A detailed analysis of well-known studies concerning this problem is given. A mathematical model, technique and algorithm for studying the dissipative properties of inhomogeneous viscoelastic systems of high-rise buildings with dynamic vibration dampers are developed in the paper, taking into account the real geometry of structures. The hereditary BoltzmannVolterra theory was used to describe the viscoelastic properties of the damper and springs material. To solve the problem, the finite element method and the Muller method were used. The natural vibration modes of the Novo-Angren TPP smokestack with dynamic vibration dampers were investigated for various damper parameters. The imaginary part of complex eigenfrequency of the system was used as a dissipative index. A number of new mechanical effects were identified. The developed technique can be used to optimize the parameters of a viscoelastic damper for a structure.
In this work, its application's theoretical and methodological foundations are developed for calculating the dynamic characteristics of shell structures that function independently or are parts of a complex mechanical system as a substructure. An important stage in the study of the dynamic behavior of the complex multiply connected shell structure under consideration is the determination of the dynamic characteristics of the structure, which include natural frequencies and modes of vibration, amplitude-phase frequency characteristics, dynamic coefficients of influence, dynamic stiffness and the coefficient of dynamicity. A solution method, an algorithm, and a program for calculating dynamic problems of structurally inhomogeneous shell systems have been developed. The developed method makes it possible to determine the dynamic characteristics of structurally inhomogeneous shell systems, numerical results are obtained, and graphs of the change in vibration frequencies depending on the inhomogeneity parameter are plotted.
The paper presents the choice and method of calculating thin-walled structures that adequately reflect deformation in the compensator example. When choosing a design model, the influence of structural elements and their mechanical characteristics on its behavior in various operating conditions is taken into account since sometimes small changes in the design model can significantly impact the design analysis results. The complete design scheme of most designs, particularly the compensator, leads to statically indeterminate systems. Taking into account the energy dissipation in the shell material; the boundary value problems are reduced to a system of ordinary differential equations of the 12th order. The forms of natural oscillations for the first four natural frequencies are given. It is established that the inertia forces acting in the axial direction do not significantly affect the stress-strain state of shell structures.
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