Model identification of damping in railway beam bridges

The evaluation of physical models able to properly reproduce the dissipative properties of railway bridges is a crucial task for fatigue life and comfort analyses. In this work a parametric model of a usual structural system (beam bridge) is adopted to determine the main damping features of real-life bridges. The results of several experimental campaigns carried on steel and concrete beam bridges of the Italian network are used. In order to identify a parametric model, the vibration signals recorded on the structures are processed resorting to a time domain technique (the Stochastic Subspace Identification, SSI, technique). The comparison among identified parametric models for steel and concrete bridges highlights the damping sources for these kind of structures in environmental conditions and under train passages. The obtained results are compared with the indications provided by the international codes and the technical literature.