Abstract:Based on a three-parameter Pasternak viscoelastic foundation model, the transverse free vibration characteristics of tapered pile of circular section subjected to initial axial pressure were investigated. The pile was simplified into a vertical linear elastic Timoshenko tapered beam-column, and the effects of pile-soil interface friction and the longitudinal variation of foundation parameters around the pile were considered, and then the dynamic governing equations for the tapered pile-soil system were derived. The solution of the equations was transformed into the first order eigenvalue problem of general linear algebraic equations with variable coefficients by means of variable separation, dimensionless and numerical simulation of the differential quadrature method. Then, the eigenvalues and eigenvectors of each order were solved by QR method. The effects of cone angle of pile, axial load on pile head, length-diameter ratio, lateral friction, soil foundation parameters around pile and their linear variation on the fundamental frequencies and attenuation coefficients of the tapered pile were discussed under corresponding boundary conditions. The results show that the natural frequencies and corresponding attenuation coefficients of tapered pile decrease with the increase of cone angle, and the critical damping decreases with the increase of cone angle, and then the coupling effect between cone angle and foundation damping is obvious. The influence of the lateral friction and the non-uniform distribution of foundation parameters along the longitudinal direction of the pile on the fundamental frequency cannot be ignored.
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