Aires Colaço

The influence of train properties on railway ground vibrations

This paper uses a sensitivity analysis to quantify the dominant train properties (mass and spacing of wheels and bogies) that contribute to ground-borne vibration generation, with the aim of reducing the complexity of train–track numerical models. This research is significant because ground-borne vibration from railways is a growing problem, particularly in urban areas. Despite this fact, attempting to predict vibration levels is complex because there are many variables that contribute to the overall dynamic response. Therefore, a deterministic approach is commonly used, that ignores many of these variables. Thus, this paper identifies the variables that can be ignored, while highlighting those that are highly influential on vibration generation. For this purpose, a previously validated 2.5D finite elements-boundary elements approach is used to simulate dynamic train–track interaction. It is computed many times for a variety of modelling variables to investigate the effect of each on the ground-borne vibration levels in the far field. It is found that increases in unsprung mass of the train causes a large increase in vibration levels. Furthermore, changes in wheel/bogie spacing and semi-sprung mass are found to have a minimal effect on vibration generation.

Study of ground vibrations induced by railway traffic in a 3D FEM model formulated in the time domain: experimental validation

Abstract In this paper, a three-dimensional numerical model is applied for studying railway vibrations. The numerical model is based on finite element method formulated in the time domain with an implicit scheme of integration. In the first part of the paper the numerical approach is briefly described. An uncoupled scheme is applied: (i) firstly the train loads are calculated taking into account dynamic excitation with a 2D vehicle-track model; (ii) the computed loads on each sleeper are introduced into a 3D numerical model, developed in the commercial code Plaxis, which is used to simulate the wave propagation in the ground. In the second part of the paper a real case study, located in Portugal, is presented, being used for the experimental validation of the proposed model. The numerical results of ground vibrations show an acceptable agreement with real measurements. Therefore, the proposed approach can be used as a reliable prediction tool based on PLAXIS software, which allows simulating railway vibrations in some specific cases such as soft soils, inhomogeneous geometries in the longitudinal direction of the track and transition zones.

GROUND-BORNE VIBRATIONS DUE TO RAILWAY TRAFFIC IN URBANIZED AREAS: A NUMERICAL STUDY ABOUT TRAFFIC IN TRENCH CROSS-SECTIONS

Modern cities require efficient mass transportation systems like subway and railway networks. Due to the lack of available space and also due to environmental concerns, it is usually preferable to use the underground space to construct such kind of infrastructures. In this context, several railway lines run in trench cross-sections in urbanized regions. This option permits to save space, allowing reducing the distance between railway lines and existing buildings. Due to that reduced distance, nearby buildings are exposed to relevant levels of vibrations that can annoys their inhabitants. In the present paper a numerical investigation about the dynamic aspects related with wave propagation due to railway traffic in trench cross-sections is presented. For that purpose, a 2.5D FEM-PML formulation is adopted for the simulation of the main system (track-retaining structure-ground), while the rolling stock is simulated by a multi-body approach. A reference scenario is previously presented, being followed by a parametric study where the influence of the geotechnical properties of the ground was analyzed. 1982 Available online at www.eccomasproceedia.org Eccomas Proceedia COMPDYN (2017) 1982-1993