Airborne and Ground-Borne Noise and Vibration from Urban Rail Transit Systems

The environmental effect of ground-borne vibration and noise generated by urban rail transit systems is a growing concern in urban areas. This chapter reviews, synthesizes and benchmarks new understandings related to railway vibration and associated airborne and ground-borne noise. The aim is to provide new thinking on how to predict noise and vibration levels from numerical modelling and from readily available conventional site investigation data. Recent results from some European metropoles (Brussels, Athens, etc.) are used to illustrate the dynamic effect of urban railway vehicles. It is also proved that train type and the contact conditions at the wheel/rail interface can be influential in the generation of vibration. The use of noise-mapping-based results offers an efficient and rapid way to evaluate mitigation measures in a large scale regarding the noise exposure generated to dense urban railway traffic. It is hoped that this information may provide assistance to future researchers attempting to simulate railway vehicle vibration and noise

MBS/FEM co-simulation for hybrid modeling of railway dynamics

Nowadays in railway traffic, specific speed limitations exist depending on the train charge, due to a fragile subsoil or even an old building that has to be preserved. Depending on the type of vehicle, the type of soil or even the vehicle speed, the groundborne vibration characteristics can significantly vary. It becomes thus important to predict the vibrations generated by a train passing on a track in the surrounding soil. In order to achieve this prediction, a hybrid modeling approach, consisting in a vehicle modeled using the minimal coordinates approach in multibody systems theory and a soil modeled using a finite element method, is developed. The recoupling of this hybrid system is performed using co-simulation between two different software packages with their own solvers. The first software is EasyDyn, an in-house C++ library package dedicated to multibody dynamics and the second software is ABAQUS that is dedicated to finite element analysis. The aim of this paper is to illustrate the results given by this hybrid model. Then two different co-simulation schemes (the sequential Gauß-Seidel scheme and the parallel Jacobi scheme) will be used and compared in terms of accuracy for this specific railway application

Review of Trackside Monitoring Solutions: From Strain Gages to Optical Fibre Sensors

A review of recent research on structural monitoring in railway industry is proposed in this paper, with a special focus on stress-based solutions. After a brief analysis of the mechanical behaviour of ballasted railway tracks, an overview of the most common monitoring techniques is presented. A special attention is paid on strain gages and accelerometers for which the accurate mounting position on the track is requisite. These types of solution are then compared to another modern approach based on the use of optical fibres. Besides, an in-depth discussion is made on the evolution of numerical models that investigate the interaction between railway vehicles and tracks. These models are used to validate experimental devices and to predict the best location(s) of the sensors. It is hoped that this review article will stimulate further research activities in this continuously expanding field

Numerical and experimental assessment of railway-induced ground vibrations generated by IC/IR trains in Brussels

Nowadays, the rising demand for new railway networks in Brussels is associated to discomfort and disturbance felt by the neighbourhood. This problem is a major concern of inhabitant surrounding rail infrastructure and causes part of the delay in the Brussels RER network construction. The present paper focuses on the vibratory nuisances generated by domestic trains in Brussels region. A compound experimental/numerical analysis is presented, based on recent investigations on line L161 between Brussels and Luxembourg. A specific site was chosen due to the presence of a singular rail surface defect which induces large ground vibrations when trains pass over. The effect of this defect is examined by means of free field ground vibrations measured during the passing of an AM96 unit, and completed by numerical results obtained from a numerical model. For this assessment, a fully 3D numerical prediction model is built, based on a two-step approach which combines multibody analysis of the vehicle and finite element analysis of the track and surrounding ground. Calculated high ground vibrations stem from singular rail surface defects. The prediction model is validated first and then used to quantify the gain brought by fixing of rail surfaces, with a reduction of local defects

Chapter Airborne and Ground-Borne Noise and Vibration from Urban Rail Transit Systems

This chapter addresses recent progress in the field of polymer thermoelectric materials. It covers a brief introduction to intrinsically conductive polymers and its motivation for thermoelectric utilization. A review about important and recent literature in the field of p-type and n-type polymers for thermoelectric applications is summarized here. For a better understanding of material development issues, doping mechanisms for intrinsically conducting polymers are discussed. Special emphasis is given to n-type polymers, since this group of polymers is often neglected due to unavailability or poor stability during processing. Different possibilities in terms of generator design and fabrication are presented. Recent challenges in this scientific field are discussed in respect to current material development, uncertainty during the measurement of thermoelectric properties as well as temperature stability for the most prominent p-type polymer used for thermoelectric, PEDOT:PSS

Building vibrations induced by human activities: a benchmark of existing standards

Vibrations in buildings impact the behaviour of structures and humans, for sources defined as internal or external to the building. Besides the comparison of vibrations to fixed limits, the choice of a relevant indicator is unavoidable and this indicator is defined differently according to the selected reference text. Various standards (or directives similar to standards) exist and this paper focuses on the most important and the most used ones, for ground vibrations induced to buildings or for human exposure inside buildings. In addition to the interest of comparing values to well-defined and well-known limits, the knowledge of these standards allows the use of suitable indicators. Various vibration signals are used, from a simple harmonic signal to complex vibrations generated by railway traffic, in order to present a relevant analysis of severity of each norm. It turns out that criteria noticeably vary from one reference to another one, and that the thresholds are different for each standard