“Ansa del Tevere” Viaduct Modal Identification – Comparison Between a Classic and an Innovative Approach

Modal identification techniques are aimed to evaluate the dynamic characteristics of complex structures in terms of natural frequencies, modal shapes and damping ratio. The acquisition and evaluation of the dynamic parameters characterizing a structure can be very useful in the calibration of accurate theoretical models; furthermore, in the last decades, dynamic analysis has been hugely employed for the monitoring of the structural health of infrastructures and structures (such as: bridges, viaducts, skyscrapers, historical buildings,…). For these reasons, the infrastructure’s modal analysis has assumed a fundamental priority and in the last decades, different methodological and techno-logical approaches have been developed. The present paper describes a dynamic analysis carried out on the “Ansa del Tevere” viaduct designed by Prof. Riccardo Morandi using the Operational Modal Analysis (OMA), which allows to analyse and study the dynamic response of massive structures, such as bridges and viaducts, using traffic loads as excitation source. The dynamic study of the viaduct has been executed using two different approaches: the first can be defined as a classic approach installing triaxial MEMS accelerometers; in the second one different high-speed cameras with the Motion Magnification (MM) technology were used. The MM technique is widely utilized with good results in the mechanical industry. The results obtained with the two different techniques are compared and discussed in the paper.