In particular, among the satellite positioning systems (American, Russian and the future European), the global positioning system (GPS) offers continuous long term acquisitions and provides sampling rates sufficient to track the displacement of long period structures, with an accuracy of the order of sub-centimetres. It is independent from negative atmospheric conditions or large temperature variations.

The effectiveness of such a SHM solution is presently under evaluation [1-5]. First, the reliability of the GPS in collecting static and dynamic 3D movements of monitored points for real time measurements has to be assessed. Second, the uncertainty of the measurements (due to sensors placement, structural identification and diagnostic processes) has to be quantified.

The steel building which hosts the authors' laboratory is the case-study within this paper. Static and dynamic tests have been realized by comparing GPS records with those of a displacement sensor (which support the moving GPS sensor). A comparison of the data collected by GPS units with those recorded by tri-axial accelerometers has also been carried out when dynamic vibrations were induced into the structure by movements of an internal bridge-crane. Different GPS unit locations on the roof of the building are then conceived to detect any signal dilution of precision (DOP) and to assess the response of the structure under long duration excitation such as those induced by strong wind events.

The study, through an experimental full-scale tests campaign, trys to confirm that the GPS is a promising tool in the field of civil engineering, and its accuracy is consistent with the monitoring requirements for flexible structures.

[1]

F. Casciati, C. Fuggini, C. Bonanno, "Dual frequency GPS receivers: reliability of precision of the measures", Proceedings of 4th C2I, Nancy, 15-17 October 2007, 604-612, 2007.

[2]

F. Casciati, C. Fuggini, "Measuring the displacements of a steel structure by GPS units", Proceedings of 1st International Symposium on Life-Cycle Engineering, Varenna, 11-14 June 2008, 501-506, 2008.

[3]

F. Casciati, C. Fuggini, "Monitoring an Industrial Steel Building by GPS Receivers", Proceedings of the 4th European Workshop on Structural Health Monitoring, Krakow, 2-4 July 2008, 219-226, 2008.

[4]

F. Casciati, C. Fuggini, "GPS Based Structural Identification and health monitoring", Proceedings of the Fourth European Conference on Structural Control, St. Petersburg, 8-12 September 2008, 133-140, 2008.

[5]

F. Casciati, C. Fuggini, "Engineering Vibration Monitoring by GPS: Long Duration Records", accepted for publication on Earthquake Engineering and Engineering Vibration, 2009.

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