Fatigue represents one of the most diffused failure modes in steel and composite steel concrete railway bridges, as it produces about 80/90% of all failures. Beside directly induced fatigue, 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 and the design of new ones.The European research project FADLESS "Fatigue damage control and assessment for railways bridges" 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.
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 vibration modes and, finally, experimental mode shapes were compared to numerical results of the preliminary FE bridge model.
The global vibration modes identified in the experimental dynamic tests were adopted as reference for the numerical updating of the FE Hinge model of Panaro bridge, that represents the actual resistant scheme of the structure. To this aim, an automatic optimization procedure was implemented by modeFRONTIER software. Objective of developed procedure was to minimize simultaneously and independently the differences between experimental and numerical eigenfrequencies by the variation of suitable parameters.