Case Studies


The monitoring aims at analyzing the behavior of post-tensioned cables during the bridge's operation, through time and frequency domain analyses. Real-time monitoring is a key tool to provide useful information for the detection of possible effects induced by ongoing deterioration or fatigue processes. The analysis allows a comparison between the expected modal parameters and the measured natural frequencies in the initial monitoring conditions, with consequent definition of corresponding attention and alarm threshold levels set for automatic alerting of the operator.
Location: Italy
Project type: Highway bridge
Sensor type: Accelerometers
Number of measurement points: 90
Number of sensors: 90
Installation period: September 2017


  • Executive system design
  • Installation assistance
  • FE modeling and continuous structural diagnostics with automatic alerting


  • Analysis of structural vibrations induced by traffic loads
  • Monitoring of the evolution over time of the response of external post-tensioned cables
  • Early detection of the first signs of cable corrosion
  • Real-time evaluation of the strands' conditions under the structure's operating conditions
  • Determination of expected cable vibration thresholds corresponding to adequate levels of safety of the structure
  • Planning of targeted maintenance interventions


Real-time monitoring of the behavior of post-tensioning cables is a key tool for providing useful information for identifying possible effects induced by ongoing deterioration or fatigue processes. The monitoring system installed, consisting of a total of 88 triaxial accelerometers, is aimed at analyzing the behavior of the cables during the operation of the bridge, whose service life depends on the behavior of the steel strands that make up its cross section. The use of MEMS accelerometers can therefore provide the operator with information on the properties of the cables necessary to determine the long-term performance of the bridge. In particular, variations in the dynamic characteristics of the monitored structural elements in terms of their natural vibration frequencies have been analyzed. A specific data processing algorithm, specifically built for the analyzed case, has allowed for efficient real-time monitoring of the cables. The signal received from the accelerometers has been purified of measurement noise and any external influences. Observation of the recorded trends during the monitoring period has allowed for the construction of a benchmark of measurements corresponding to the standard behavior of post-tensioning cables subject to standard traffic conditions and/or other assumed non-exceptional external loads, with the consequent definition of corresponding levels of attention and alarm thresholds set for the monitoring system. The threshold levels have been determined based on a considerable number of vibration data of the cables under standard traffic conditions. The monitoring system is also capable of controlling the response of the bridge following accidental actions, such as possible earthquakes with an epicenter near the bridge.


Gli accelerometri installati sui cavi restituiscono valori di accelerazione lungo tre assi X, Y e Z la cui analisi è svolta nel dominio del tempo e delle frequenze. L’analisi nel dominio del tempo delle accelerazioni, registrate dai sensori installati sui cavi, viene svolta al fine di valutare i livelli vibrazionali degli stessi mentre la sintesi nel dominio delle frequenze permette un confronto tra i parametri modali attesi e le frequenze proprie misurate nelle condizioni di inizio monitoraggio (stato zero). Un eventuale discostamento tra i valori teorici e le grandezze misurate può fornire indicazioni per l’individuazione dei cavi che presentato potenziali riduzioni di rigidezza in atto o subiti in passato. Eventuali salti dei picchi di frequenza registrati durante il periodo di monitoraggio sono considerati potenziale indice di danneggiamento mentre i cavi che non presentano registrazioni di eventi significativi sono considerati lo ‘standard’. Sulla base dei valori di soglia impostati per l’osservazione dei dati, definiti alla luce delle osservazioni derivanti dal monitoraggio in continuo e calibrati in funzione degli eventi registrati e dell’analisi strutturale di riferimento, l’eventuale superamento di soglia permette la segnalazione di un comportamento del cavo che si discosta dal trend considerato standard, che viene pertanto classificato anomalo, segnalato al gestore ed indagato con maggiore attenzione.


Case history


The monitoring system has been specifically designed in terms of number and positioning of sensors to capture the complex dynamic response of the structure. By means of FEM modeling of damage scenarios, appropriate dynamic thresholds have been calculated for the continuous monitoring of the state of the stays and the evolution over time of the response of the footbridge deck.

The monitoring system consists of 28 transverse measurement sections aimed at controlling the tensile and deformation evolution of the tunnel lining over time. The monitoring system, consisting of MEMS inclinometers integrated with post-installed local tension-deformation sensors within the lining, allows for both local and global monitoring of the structure's response. The diagnostics are complemented by nonlinear FEM modeling and a real-time alert service for any structural issues.
The structural monitoring and diagnostics of the two tunnel tubes are supported by a complex non-linear FEM modeling, through which, for each monitoring section, the deformation and the evolution of its ovalization with respect to the evolution of the ongoing landslide phenomenon are evaluated. In cable sections where the mechanical characterization and the surrounding stratigraphic conditions are completely similar, a Data-Driven approach is used to extend the Performance Indicators and monitor the most significant structural response parameters at all measurement sections.
The monitoring allowed the real-time control of the response of the deck of a span during open traffic restoration works, and was subsequently extended to the entire viaduct for static and dynamic behavior control over time. The Model Driven monitoring approach allowed the investigation of the main damage scenarios of the structure and the definition of Performance Indicators on which to set threshold values and conditions.
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