In the adaptation of mobile telephony infrastructures, the need to strengthen the antenna-holder structures is increasingly emerging. The classic hexadecagonal poles often have significant heights (24-36 m) and thin thicknesses (4-8 mm). Consequently, in order to support the technological modernization that the network needs, with the installation of new equipment and antennas of new generation, we are often faced with scenarios of structural overexploitation, if not even conditions, in theory, of incipient collapse at the SLU.
Normally a reinforcement intervention for a hexadecagonal pole consists in the realization of vertical support braces and/or in the adaptation of the foundation works
A hypothetical objective function of the design of such reinforcements would be guided by the driver of the best structural performance of the reinforcement solution, conditioned by
Financial sustainability (costs)
Technical difficulties of realization (Feasibility)
The goal of the best structural performance, in the safeguard of costs and feasibility, is first of all a design theme, which must be carefully calibrated on the basis of accurate structure modelling, that is, a modeling that privileges aspects like: the geometry of the used profiles, the static current and the correct modeling of the connections of the nodes between the members.
We analyzed 4 different reinforcement solutions, for the same polygonal pole subject to the same load pattern, obtained through FEM analysis with plate and beam elements, in the wind condition at the SLU
In the bubble diagram of figure 1 we have reported, for each solution, a synthetic evaluation of:
- structural performance
- construction costs
- technical difficulties (bubble size)
From the reading of the diagram they are inferred very interesting considerations:
- solutions A and B perform well and in a way that is equivalent, but B has greater feasibility
- the solution C is the most technically performing and at the same time the most financially sustainable, the realization difficulties are slightly higher than A and B;
- the reinforcement D is the solution that reveals a performance slightly inferior to A eb, however against costs significantly greater, the realization difficulties remain analogous.
To make use of the above results, the performance of the respective solutions is shown in the diagram of figure 2, keeping constant the raw costs, relative to the production of the carpentry.
Also from this graph it emerges that the reinforcement design, guided by a modeling able to read the behavior of the structures, pays the costs of realization with the best performance.
Equally, accurate modeling highlights all the limitations of the most expensive solution.