CONICET | Buscador de Institutos y Recursos Humanos

As wireless communications spread, there is an increasing demand for antenna supporting structures. Lattice towers are commonly used systems, either self-supported or guyed. The latter are chosen for economical reasons when there is enough space for their location. Radio and television employ structures that range between 100 and 600 m and communication towers for mobile phones are around 60 m though higher structures are also constructed. For large heights, guyed masts are indicated. However, it depends on the customer preferences, suppliers, budget and location. Generally, self-supported structures are preferred in urban areas and guyed masts in the countryside. Nowadays the demand for more accurate and reliable communication systems poses higher structural demands since the signal technology sometimes requires of very small motions of the supporting structures to achieve a high quality transmission. The design of these structures is, in general, carried out following the standard codes and simplified models. The dynamic actions, as wind and earthquakes, are not addressed in detail with exception of special cases, despite the large potential of adverse impact. Guyed structures stiffness are highly dependent on the guys tension. The influence of this parameter is relevant to the dynamic response. Also, the mast stiffness and damping are variables of interest. In this work, the dynamic response of a communication lattice guyed tower is analyzed under wind loads and the degree of influence of the mentioned parameters is assessed. The mean wind load is derived from the standard's approach while the fluctuating wind component is obtained through the Spectral Representation Method (SRM). The algorithm starts from a given Power Spectral Density (PSD). The temporal and spatial correlations are taken into account by finding the cross-spectrum and introducing a coherence function. The method yields a temporal record of the fluctuating wind velocity for each desired height of the tower. It is possible to show that the wind velocity thus found can reproduce the starting point PSD. Once the wind velocity is introduced in the wind pressure expression of the standard code CIRSOC-INTI (2005), the fluctuating loads are derived for the mast. A finite element discretization is employed with these loads using an equivalent beam model for the lattice tower and truss elements with pretension for the cables (guys). A standard case with fixed values of guy tensions, tower stiffness and damping is first considered. Then, the three parameters are varied within practical ranges. Some outcomes of the dynamic response are analyzed, e.g. mean, minimum and maximum values of the top displacement of the tower and the dynamic tension of the cables. Several plots are derived to stress the influence of the parameters. Results are compared with a previous study in which a fully correlated load was assumed, i.e. the wind velocity was generated as a combination of harmonic deterministic functions.

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