This study investigates the free vibrations of elastically constrained shear and Rayleigh beams placed on the Pasternak foundation. Of particular interest, it is aimed to analyze the influence of shear strain, rotational inertia, elastic stiffness, and shear layer on the natural
frequencies and eigenmodes of beam vibrations. For this purpose, the eigenfrequencies and eigenmodes are determined using analytical and numerical techniques. A finite element scheme is developed employing quadratic and cubic polynomials for slope and transverse displacement, respectively. The efficiency and accuracy of the finite element method are illustrated by comparing it with the analytical results for generalized and special cases. The underlying model analysis justifies that the natural frequencies of the beam vibration depend only on the geometry of the Rayleigh beam, while these frequencies depend on the physical and geometric properties of the shear beam. However, the natural frequencies of the Euler-Bernoulli depend solely on the geometric conditions of the beam.
This article presents a modal analysis of an elastically constrained Rayleigh beam that is placed on an elastic Winkler foundation. The study of beams plays a crucial role in building construction, providing essential support and stability to the structure. The objective of this investigation is to examine how the vibrational frequencies of the Rayleigh beam are affected by the elastic foundation parameter and the rotational inertia. The results obtained from analytical and numerical methods are presented and compared with the configuration of the Euler–Bernoulli beam. The analytic approach employs the technique of separation of variable and root finding, while the numerical approach involves using the Galerkin finite element method to calculate the eigenfrequencies and mode functions. The study explains the dispersive behavior of natural frequencies and mode shapes for the initial modes of frequency. The article provides an accurate and efficient numerical scheme for both Rayleigh and Euler–Bernoulli beams, which demonstrate excellent agreement with analytical results. It is important to note that this scheme has the highest accuracy for eigenfrequencies and eigenmodes compared to other existing tools for these types of problems. The study reveals that Rayleigh beam eigenvalues depend on geometry, rotational inertia minimally affects the fundamental frequency mode, and linear spring stiffness has a more significant impact on vibration frequencies and mode shapes than rotary spring stiffness. Further, the finite element scheme used provides the most accurate results for obtaining mode shapes of beam structures. The numerical scheme developed is suitable for calculating optimal solutions for complex beam structures with multi-parameter foundations.
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