Objectives of the service
A Structural Health Monitoring system can be a benefit for civil and other engineering industries where visual interval-driven inspections are the main (and in many cases the only) type of checks. Health monitoring can support users in defining and improving maintenance strategies and procedures. Structural health monitoring can give direct data about the actual status of a structure and not just an estimated probability figure based on statistical patterns.
Use of satellite services is a key point for the development of a complete end-to-end service that meets the user requirements. The proposed service is based on a suitable integration of various technologies such as: telecommunication, networking, structural analysis, data transfer, etc.
The objective of the feasibility study is to assess the technical feasibility as well as the commercial viability of such a monitoring service.
Users and their needs
Two major target users have been identified for the SHM for telecom towers service:
Owners and managers of telecom towers: such as Rai Way S.p.A. which is the the major Italian broadcasting company and took part in the feasibility study as the reference user. It uses a large number of telecom towers to transmit TV signals over the Italian territory.
Telecom towers manufacturers such as Calzavara, another reference user and a company operating in the Italian and international markets in the telecommunications and energy fields.
Service/ system concept
Both the users are extremely interested in a structural monitoring service for their towers in order to have data and reports which help the companies to better plan the inspections and to increase the awareness of a current status of a tower.
In addition, the companies could also monitor the tower in special environmental conditions such as storms or snow. The system must be able to provide the user with data that are helpful in the structural assessment of the stable behavior of the tower and to inform the user if the nominal behavior changes. The data provided by the system will be accessible by the companies by means of a protected web-based service.
Space Added Value
The main space assets envisaged in the project are the GPS and satellite communication.
GPS nowadays is normally used to precisely measure structures, for field surveying, GIS and in large-scale constructions. Various services and COTS devices are available, with different level of precision, to support the different needs of these applications. GPS can be used for static monitoring of towers and terrain movements with adequate accuracy.
Terrestrial communication is more relevant in a country such as Italy where the mobile telecommunication infrastructure is well developed and functioning almost everywhere. This solution can cover the necessary data rates at a slightly more advantageous cost with respect to satcom. However satellite telecommunications for the transfer of the monitoring data can be required for TV/Radio broadcast towers that are not equipped with GSM transceivers and located in places where weakly, if none, coverage is provided by the mobile network. The added value of satcom has been outlined for user groups such as Calzavara which, in addition to manufacturing services offers a complete maintenance service for their customers located all around the world. Satellite telecommunication would provide a global coverage and a unified solution for all the data traffic from their worldwide towers (equipped with the proposed SHM service) to their control centre. The satcom solution favours a fast and reliable implementation where ground infrastructures are not present or require a long time to be set in place
The Feasibility Study was concluded after the Final Review meeting which took place in June 2014. In the coming months the Consortium will work on solving issues, which are necessary to go to the demonstration project phase; after which, the outline proposal for the demonstration project will be prepared and submitted.
During the Feasibility Study, it was demonstrated that with a reduced set of sensors (among them a piezoelectric transducer, a temperature sensor, an anemometer and two GPS receivers) it was possible to acquire a sufficient amount of raw data to feed into our processing software. The latter was able to output key structural, loading and environmental parameters which were used to support the analysis of the status of the structure under monitoring.
In particular, we were able to identify the resonance frequencies of the tower and monitor its evolution with respect to the environmental conditions. We have been able to estimate and monitor the position of the tower using the GPS receiver with an accuracy in the order of the centimetre. We have also established a link between the instruments (sensor nodes) and the control centre and made available the results of the experimentation in real-time via the internet.
The test performed at Monte Mario tower was successfully conducted for a validity period of a month (from mid-March to mid-April), where the full end-to-end service provision chain was implemented. Aspects related to service provision such as the availability, the quantity and quality of data have met the user requirements as in the case of an operationally running service. As of mid-June 2014, the sensor network was still mounted on the tower of Monte Mario and the data were still being delivered to Raiway.
The sensor network had several advantages w.r.t. to previous installations on the test tower:
- The sensor nodes were compact and easy to install on the target tower.
- The sensor nodes were wireless and therefore there was no need to install bulky long wires on the tower. This property allowed to reduce considerably the installation time and augment the reliability of the system.
- The sensor nodes were independent and autonomous from a power point of view.
The information obtained from the processing of data coming from local sensors could be used, by the customers, for updating the maintenance plan according to the actual condition of the monitored towers. This opportunity represents an improvement with respect to the present situation, where maintenance activities are planned on a pure statistic basis, and consequently subjected to the risks of performing interventions that prove, in the hindsight, to be unnecessary.
The interactions made with potential customers allowed the consortium to identify the business model fitting the customers’ needs: having the most critical infrastructures monitored. The envisaged service consists of a processing system installed within the user control centre, which processes the information acquired by the local sensor networks and displays index and parameters sensitive to the integrity status of the towers. The service includes also assistance for the customers, which will be provided in a customized way, in accordance with specific necessity of any customer.