PREDICTIVE MODEL OF VIBRATIONS INDUCED BY RAILWAY TRANSIT IN URBAN AREAS

The structural increase of rail networks in recent years, aimed at transforming existing lines in high speed and/or high capacity lines, implies an increase of stress resulting from a more intense exercise and a more rapid evolution of the decay of rolling stock and infrastructure, highlighting noise and environmental damage caused by vibrations. In recent years, rail transport systems have often been subjected to complaints from the population living near railway lines, where the annoyance is usually caused by the emission of noise and vibrations. This problem, coupled with the growing sensitivity to the environmental impact, requires the increasing study of vibrations and sound, both for new infrastructure and for the adaptation and the upgrading of existing lines. Railway vibrations are secondary localized wave motions, due to the dynamic interaction between several complex mechanical systems: rolling stock, wheels, rails and trackbed. Such vibratory motions propagate in the ground-born, generating different dynamic effects on the receptors; these effects can disturb or damage facilities and people. The evaluation of the vibrational noise due to railway transport systems requires the analysis of the whole phenomenon: the generation, due to the interaction between the train and the way, is considered first; then the propagation phenomenon, influenced by surrounding soil, is studied. The aim of this research is to promote a predictive methodology of vibrations induced by metropolitan lines in Naples, due to rail defects; the propagation phenomenon is studied through a "hybrid" model, divided into two sub-models: the former, called "generation model", analyzes the dynamic interaction between the rolling stock and railway equipment; the second, called "propagation model", studies the propagation of vibration waves by means of the finite element method, applying the interaction forces on the superstructure. An adequate data set of experimental vibrations measurements is used to validate the proposed methodology.