Influence of Guy Rupture and Plasticity on the response of Guyed Telecommunication Towers

Resumo

A large number of tall guyed towers consisting of a mast laterally supported by pretensioned cables
have been recently built due to an increasing demand for taller antenna towers. The cables act as a supporting
system, increasing the towers critical load and natural frequencies. Their influence depends on the number of guy
levels and the distribution setup. However, many accidents have been reported involving guyed towers, being
cable rupture one of the frequent causes of structural failure. Here, the sudden rupture of one or two, arbitrarily
selected, cables on the linear and nonlinear response of the guyed tower under static and dynamic loads is
investigated. Also, the elastoplastic behavior of the mast and cables is taken into account. For this, models
consisting of a mast supported by different cable set ups are investigated. The analysis is conducted using the finite
element software ABAQUS. The mast is modelled using three-dimensional beam-column elements and the cables
using tension only truss elements. Thus, the tower-cables interaction leads to a highly non-linear behavior under
static and dynamics loads. First, the critical load and natural frequencies of the structure are determined for the
intact structure and for configurations missing one or two cables. Coincident buckling loads and vibration
frequencies are observed due to the symmetric cable distribution around the tower. This symmetry condition may
lead to interactive buckling and internal resonances, increasing the effect of the nonlinearities on the response of
the structure. Then the nonlinear post-buckling behavior is studied using the Riks method and the influence of
rupture and plasticity on the tower load carrying capacity is evaluated. Finally the influence of cable rupture and
plasticity on the free and forced vibrations of the tower is investigated.