Radar-based operational modal testing of large structures: two case studies in Spain

Ground Based Radar Interferometry is a recent experimental methodology, suitable to provide non-contact measurement of deflections on large structures, in static or dynamic conditions. In the last decade the development and application of this microwave remote sensing tool has drawn the attention of several researchers and the number of case studies reported in the literature is increasing and especially focused on ambient vibration testing of bridges, buildings, ancient towers, chimneys and wind farms. This paper addresses the application of microwave remote sensing in operational modal testing of two outstanding large structures located in Spain: the Communication Tower of Collserola, close to Barcelona, and the bridge crossing the Ebro River at Amposta. After a brief introduction of the adopted radar technique, the main results of the two experimental surveys are presented and discussed. The experimental investigation confirms the reliability of the radar survey to clearly identifying the key dynamic characteristics of large structures as well as the simple and safe way of carrying out measurements.