A combined numerical/experimental prediction method for urban railway vibration

Railway-induced ground vibrations can cause negative effects to people/structures located in urban areas. One of the main sources of these vibrations is from the large vehicle forces generated when train wheels impact local defects (e.g. switches/crossings). The sole use of traditional in-field transfer-mobility approaches is well suited for plain-line assessments, however is more challenging when discontinuities are present, due to the generation of large magnitude impact forces. This paper presents a hybrid experimental-numerical approach that can predict ground-borne vibration levels in the presence of a variety of railroad artefacts such as transition zones, switches, crossings and rail joints on existing networks. Firstly, the experimental procedure is described, which consists of multiple single source transfer mobilities to determine the transmission characteristics between rail and nearby structures. This is then coupled with a combined multibody vehicle and track numerical model, which is capable of simulating vibration generation in the presence of railway discontinuities. The resulting model is advantageous over alternative approaches because it can account for complex railway discontinuities, while at the same time incorporating the large uncertainties associated with different soil configurations. It is used to analyse a case study, where it is shown that vibration levels are strongly dependent on vehicle speed, defect type and defect size.