A hybrid two-step approach for evaluating the impact of local rail defect on building vibration.

With the development of light rail transit in urban areas, the effect of railway vibrations on buildings and people inside buildings is a growing problem. In particular, urban transit commonly generates large vibration levels at rail discontinuities, and thus this paper presents a 2-stage numericalexperimental vibration prediction methodology. The first step is purely numerical and focuses on the vehicle-track dynamics by analysing the effect of local defects at the rail surface during train passage. A multibody vehicle model and a flexible two-dimensional track are coupled using Herzian contact theory, which includes the geometry of the studied defect. The results obtained capture the interaction between the railway vehicle and the track, which serves as input for the second step. The latter uses experimental source transfer mobilities obtained on-site. This offers a way to accurately evaluate the soil-structure interaction which occurs in a complex medium such as the ground in urban areas. Structural response is then calculated by combining the two approaches. An illustrative example is presented, where the effect of various rail defects in the tram Brussels network is analysed. It is shown that it is possible to quantify vibration levels on light rail transit lines, where tramway networks interact with local rail defects and where railway ground vibration are problematic.