REINFORCED CONCRETE CYLINDRICAL TOWER PROJECT FOR CELLULAR TELEPHONY AND TELECOMMUNICATIONS IN MODENA

CLIENT: Vodafone Italia S.p.A.
SERVICES RENDERED: structural executive project
BEGINNING/END OF WORKS: 2003-2005

PROJECT DESCRIPTION

The present work concerned the design of the cylindrical reinforced concrete tower for cellular telephony and telecommunications located in Modena.
The structure as a whole is composed of a reinforced concrete tower of tubular section with a diameter of 2.50 m and a total height of 47 m. The tower is placed, with its prominence, inside the shed destined to be the transmission site, therefore up to a height of about 5.0 m it is concealed from view.
The tower is equipped with five levels of terracing in metal carpentry. The horizons are equipped with tubular uprights arranged radially towards the outside of the tower itself in order to be able to place transmission dishes on them. The deck beams of these terraces are also arranged radially with respect to the center of the tower. Said beams are hinge-bound to the wall of the shaft, with a vertical tubular metal tie-rod connected to the reinforced concrete platform that has the static value of acting as an indirect end-bond for all four platforms. The connection between the shaft and the slab, with casting of the two components carried out in successive phases, consists of sleeves and bars, both threaded, for joining the reinforcements without overlapping.
Particular mention should be made of the study of the wind profile performed in the frequency domain; the determination of the wind profile was carried out in accordance with the regulations in force in Italy, while the aerodynamic analysis of the wind on the shaft (study of the shape coefficients) was performed in accordance with EC1 and the most recent bibliographies on the subject.
In this way it was possible to take into account, through the determination of Reynolds number, the roughness of the surface invested by the wind, the slenderness of the structure (height-diameter ratio) and the wind speed at each point examined. By doing so, it is possible to determine the shape coefficient which better captures the real behavior of the structure as a whole with respect to what is indicated in the Italian Norm in force.
It has been also carried out the dynamic analysis of the structure with the research of the first vibration mode in order to find the dynamic coefficient Cd for the structure. This research has been carried out with the help of the writings of Prof. Solari and allows to find the multiplier coefficient of the wind thrust due to the gust behavior of the same. This Cd value is introduced numerically as a multiplier of the wind load of static character. The tower foundation consists of a square plinth placed on drilled piles. The piles reach a depth of 26.0 m., penetrating into the gravel level present from 23 m onwards. Up to this height they cross silty-clayey-sandy layers which, also due to the presence of the water table, do not guarantee the required capacity of the piles. Non-destructive tests were also carried out on the piles by means of ultrasonic cross-hole in order to check the optimal realization of the piles in terms of both depth and compactness of the casting itself.
Finally, the execution of detailed calculations on the stability of the front of the excavation in the execution of the foundation plinth made it possible to avoid the costly construction of a bulkhead containment excavation, required in a hurried manner and without technical justification by the contractor.