A telecommunication tower is a bit like a colossus with clay feet. Tubular structures are well suited to support the equipment required for the optimal operation of our smartphones. Their height of up to 50 metres, however, exposes them to wind forces that can cause fatigue failures. To keep Aeolus in check, CIMA+ has developed liquid dampers to be installed on top of these monopoles. This is a major technological innovation.
“When you bend a paperclip for the first time, it doesn’t break. But if you multiply these deformation cycles, it will ultimately break,” explains Jérôme Isabelle, structures and telecommunications project manager at CIMA+. The same phenomenon occurs with telecommunication towers: they sway millions of times in the wind during their lifetime. “Some structural elements, such as the base plate and the junctions between the various sections, can display signs of wear over time,” he points out.
If nothing is done to correct the situation, these towers may even collapse, a rare occurrence that has happened in Canada, but never in Québec so far. Rolling out 5G technology isn’t going to alleviate this: the telecommunication infrastructure parks, of which some elements are already aging, will soon have to accommodate new equipment, ergo additional loads. “This represents an opportunity for the major players in this sector to ensure the compliance of their structures and avoid this type of accident,” believes the engineer.
Off the Beaten Path
There are two possible ways to achieve this. One is to increase the fatigue strength of all weak points on a telecommunication tower. This can involve reinforcing the joints with stiffeners or adding anchor bolts at the base of the structure. This approach can be fastidious and expensive. The other approach, favoured by the CIMA+ experts, is to reduce the forces causing the fatigue. “We looked at the forces experienced by these structures and decided to control the oscillations and vibrations,” says Jérôme Isabelle.
How? By installing tanks of a mixture of a few dozen litres of water and antifreeze at the top of the towers so that they “work better.” These liquid dampers—that’s how they’re actually called—are built to counteract the effects wind has on such structures, which varies from case to case. “Their dimensions are never the same,” explains Joshua Castellanos, a telecom structures engineer at CIMA+. “They depend on the dynamic properties of the structure, and mainly on its natural oscillation frequencies.”
The development of this new technology in Québec was carried out independently by CIMA+. “We needed to find a balance between ease of installation and the ability to calibrate down the line,” says Joshua Castellanos, referring to a system designed to empty and refill the tank as needed. The development process also required advanced dynamic modelling in order to predict the behaviour of structures with liquid dampers at their summit. “We went beyond what is usually done in engineering,” he says with pride.
More Than One Innovation
Designing liquid dampers destined to tubular telecom structures began in early 2021. The first units were installed late that year. “The reduction in wind-induced movement is on the order of 30% to 50%, which is quite notable. Not only that, but the reduced movements resulting from the presence of these dampers increase the quality of the cellular signals carried by these antennas,” says Jérôme Isabelle. In other words, even the telecommunications companies’ customers benefit from this innovation!
This eliminates the need for interventions normally required to increase the strength of telecommunication towers. In other words, it is a simple, effective and, above all, a money-saving solution to a complex problem. “We now have recognized expertise in the dynamics of telecommunications structures in Québec. Even our competitors consult with us, and that says it all!” concludes Jérôme Isabelle.