Dynamics of a guyed tower through a simplified approach

CARLOS P. FILIPICH; MARTA B. ROSALES; FERNANDO S. BUEZAS

Congreso; 11th Pan-American Congress of Applied Mechanics - PACAM XI; 2010

Guyed towers are one of the most usual structural systems employed in the wireless, microwave communication industry. In particular, lattice towers are extensively used to support antennas of different sizes, shapes, and locations and they are an example of structures with nonlinear behavior even under service conditions. This paper deals with the dynamic problem of cable supported structures, in particular a guyed tower, and an analytical solution is proposed. The structure is composed of two main structural elements: the guys (cables) and the tower (mast). At this stage a simplified plane model of a tower and two cables is tackled. When dealing with towers the cables are often highly prestressed which causes the cable sag to be small. It is quite usual to use a parabola to model this type of cables. However it is known that this approximation could not be appropriate when the cables are inclined. On the other hand, the extensibility of the cables should be taken into account when cables are taut. In this work the equations governing the dynamics of extensible cables (both slack and taut) are stated without approximation. The constitutive equation used for the cables is consistent with the Mechanics of Continuum laws and comprises the well-known Strength of Materials relationship but, at the same time, it is capable of capturing the high sensibility of the non-linear problem. An equivalent beam-column represents the latticed tower introducing the shear to consider the truss flexibility. Additionally the second order effect of the vertical loads on the mast is accounted for. Due to the interaction between the mast and the cables, axial and transverse displacements are coupled. A simplified approach is explored which is the dynamics of the system with the quasi-static behavior of the cables. The system is finally solved with a finite element modeling.