The functionality maintenance of infrastructures like bridges is acquiring more and more importance due to the huge economic losses related to the interruption of their regular service. This critical aspects is more stressed considering that new and existing bridges will be included in the new Trans-European Transport Network. In particular, fatigue represents one of the more diffused failure modes occurred in steel and composite steel-concrete bridges: in fact about 80/90% of failures in steel structures are related to fracture and fatigue. Railway bridges endure million of stress cycles during their life and they are expected to be highly vulnerable to such phenomena. Moreover, phenomena like "vibration induced" and "distortion induced" fatigue are still partially uncovered by actual design codes and represent a critical aspects for the assessment of existing bridge remaining life and for the design of new bridges.

The European research project FADLESS "Fatigue damage control and assessment for railways bridges", funded by the European Research Found for Coal and Steel (RFCS), aims to define innovative technical guidelines for the assessment and control of existing and new bridges with regard to fatigue phenomena induced by vibrations and distortions produced by train passage. To this purpose, the Project will employ experimental and numerical techniques in order to evaluate properly the fatigue damages on critical details induced by vibration and distortion phenomena, taking into account the dynamic train-bridge interaction effects and the actual traffic spectra on European railway lines.

In this paper, preliminary studies performed on the Italian case study, the Panaro Bridge, are reported. In particular, results of the standard fatigue assessment according to Eurocode rules were compared with the actual fatigue damages occurred to deck secondary components to obtain a preliminary critical review of adopted fatigue assessment methodologies. Moreover, experimental tests were designed and performed on the bridge in order to identify global and local vibration modes and to evaluate the strain time-histories under train passages of critical details. Finally, experimental global/local mode shapes were compared to numerical results of the preliminary FE bridge model.