Hybrid model for rail fasteners stiffness optimization in railway-induced ground-borne vibration problems

Rail fasteners stiffness has a key role in the vibration induced by railway traffic to the surrounding buildings. This is the reason why in most cases, one of the proposed solutions for the mitigation of excessive vibration levels in nearby buildings close to an operating railway line is a change of the rail fastening system. In this article, a methodology for the optimization of the fasteners stiffness in terms of the vibration level predicted inside the building is presented. The methodology is based on a hybrid model of the global system, which models the vehicle as a moving three-dimensional rigid multibody system, the track as two Euler-Bernoulli beams periodically supported by springs that represents the rail fasteners, the tunnel and the near ground using a two-and-a-half dimensional finite element and boundary element model, and the tunnel-building response using experimental measurements on the existing site. The optimization process is much more affordable in terms of computational time thanks to the use of a semi-analytical model of the track, instead of a whole two-and-a-half dimensional finite element and boundary element model for the track/tunnel/ground system. The validity of the model hybridisation with experimental measurements to take into account the building response is discussed with different theoretical studies.