Dynamic analysis of guyed towers

SERGIO PREIDIKMAN; JULIO C. MASSA; BRUNO A. ROCCIA

Revista Internacional de Desastres Naturales, Accidentes e Infraestructura Civil

Universidad de Puerto Rico

Lugar: Mayagüez, PR 00681-9041, Puerto Rico; Año: 2006 vol. 6 p. 27 - 40

1535-0088

A numerical approach capable of predicting the dynamic behavior of guyed towers commonly used for wireless communication, meteorological measurements, and recently, even for power transmission, is presented in this paper. In order to carry out numerical simulations in a simple way, the three/four-legged latticed mast is modeled as a beam-column standing on a set of massless, non-lineal springs which represent the guys. The base of the mast is modeled as a hinge preventing the displacements. The equations of motion are discretized in the space domain using the finite element method. Because the inherent non-linear behavior of tall guyed masts, geometrics nonlinearities are included in the finite element procedure. A geometrical stiffness matrix is included to account for the influence of the axial force acting on the mast on the transverse vibrations of the guyed tower; this matrix is obtained from the nonlinear component of the strain-displacement relation. The cables are idealized using the classic parabolic model, valid for small strain elastic catenaries. Self weight and inertia of the cables are neglected. The legs, diagonals and horizontal members of the mast are modeled as a two-node, bi-dimensional elastic beam-column element with two degrees-of-freedom at each node. Nonlinear dynamic response is computed in the time domain using a predictor-corrector method to perform a step-by-step integration of the governing equations of motion. The results provided by the non-lineal model were compared with those obtained from the linearization commonly used in practice. It is shown that the model can predict reasonably well the response of cable-supported towers even with fewer degrees-of-freedom, compared to more elaborate analyses, involving finite element discretization of cables.