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In this paper, a numerical tool based on the Monkey-tail fundamental lumped parameter model is proposed for the simulation of dynamic soil-structure interaction (SSI). The proposed model has been implemented in the OpenSees finite element environment where the input parameters are merely function of the soil properties. The ease of use, accuracy and versatility of the proposed model is demonstrated in order to encourage its use within, among others, the practicing engineers’ community. Furthermore, the influence of the SSI and local soil conditions (i.e., site effect) on the seismic response of two 5-storey steel moment-resisting frame buildings has been investigated. Preliminary results shed light on the influence of these two geotechnical aspects on the structural seismic response where peak floor displacements and inter-storey drifts considering the SSI are even larger in the lower stories than those of the fixed base case. Furthermore, the results revealed the dependence of the soil amplification factor on the fundamental period of vibration, seismic intensity level and soil stiffness which are not taken into account by the current European design codes.

The interest of scientific and technical communities in the re-radiated noise phenomenon has been increasing over the last years, motivated by complaints of inhabitants living in buildings located next to sources of vibrations. The study and quantification of low-frequency noise levels inside these buildings demand accurate methods of prediction. Thus, the present paper aims to contribute to the listed goal by presenting an experimental validation of a 3D FEM-MFS hybrid numerical model, where the Finite Element Method (FEM) is used to evaluate the structural response and the Method of Fundamental Solutions (MFS) is adopted to assess the acoustic response inside a closed space. The experimental work carried out consisted in the excitation of a reduced-size acoustic chamber by applying an impulse load induced by an instrumented hammer. The structural and acoustic dynamic responses of the system were simultaneously monitored by a set of accelerometers and microphones. The case study was then modelled and the experimental data compared with the numerical results, showing that the numerical approach used is efficient and accurate, as it correctly addresses realistic situations involving re-radiated noise by elastic structures.

The numerical assessment of the dynamic response of buildings exposed to railway traffic usually requires advanced numerical models that take into account the three-dimensional character of the problem. However, engineering practice requires simple and efficient methodologies. Thus, in order to reduce the uncertainties associated with the prediction procedure, a hybrid approach is formulated, combining numerical/experimental results and post-processing techniques. The underlying concept of the methodology is the so-called SSI (soil-structure interaction) curves, which, when applied to the input motion experimentally evaluated in free-field conditions, can replace the kinematic effects induced by the presence of the building, avoiding their consideration in the simulation of wave propagation on the ground. Following the introduction of an innovative and simple approach, a numerical application example involving vibrations induced by railway traffic is presented, clearly showing the potential of the proposed methodology in assessing the building’s dynamic response to railway traffic in the vicinity.

In this work, ground-borne vibrations due to pile driving impact are analyzed. A comparison between numerical results and experimental responses obtained in a low strain test measurement is presented. The experimental campaign is held at a construction site next to the Faculty of Engineering of the University of Porto (Portugal). The low strain test is carried out with 13 accelerometers equally distanced in a straight line and the ground vibrations are measured at the ground surface for several blows induced by an impact hammer. Soil properties and stratification are determined through non-intrusive geophysical tests - seismic refraction tests and SASW (Spectral Analysis of Surface Waves) tests. The numerical model is developed in time domain with the same characteristics of the construction site, considering a finite element axisymmetric formulation and an effective semi-explicit/explicit time marching procedure. The numerical results present good agreement with the in situ measured response, which indicates the effectiveness of the developed numerical model. In the sequence, a parametric study is developed and the results compared to previous numerical and experimental studies available in the literature.

The use of pile driving techniques in urban environments demands accurate methods to predict and mitigate the potential discomfort of residents of neighboring buildings. In this context, a numerical model to predict ground-borne noise and vibrations in buildings induced by pile driving is proposed in the present paper. The model is based on a sub-structuring approach, in which the entire propagation medium is considered, from the vibration source to the receiver. The pile-ground domain is simulated by an equivalent linear FEM-PML approach formulated under axisymmetric conditions taking into account the pile-hammer interaction. The building simulation is performed using a 3D FEM approach, adequately adapted to include the soil-structure interaction, while the acoustic field induced by the structural vibration is analysed using a 3D MFS model. The levels of ground-borne noise and vibration inside the building resulting from pile driving are assessed through an application example, clearly showing the potential of the proposed methodology.

The assessment of vibrations induced by railway traffic is a complex issue that demands numerical tools for prediction of its generation and propagation along the track-ground-building system. For that purpose, this paper presents a 2.5D FEM-MFS model for modelling the track-ground system, where the Finite Element Method (FEM) is used to model the complex geometries of the track and the Method of Fundamental Solutions (MFS) to model the infinite ground. The main feature of this methodology is its ability to deal with any generic track-ground cross-section and soil properties in an efficient way, allowing modelling large domains with a reasonable computational cost. In the same numerical tool, a 3D FEM model is used for modelling the building, with the soil-structure interaction being considered in a simplified way. An experimental case study is presented and explored, allowing the experimental validation of the proposed methodology and stressing the potentialities of the model on the study of vibration propagation problems induced by railway traffic.

This paper presents a comprehensive experimental campaign developed on a stretch of the Portuguese railway network. The experimental work includes three fundamental and complementary components: the characterization of the ground, the characterization of the track and the measurement of the vibrations generated by railway traffic. The characterization of the ground was performed using a combination of conventional and geophysical tests (cross-hole and SASW). The mechanical characterization of the track was performed through receptance tests and the rail unevenness profile was accurately measured. The vibrations due to the passage of more than 20 trains were measured. First, a selection of the results is presented and analysed in detail; later, the variability of the responses is briefly discussed. The presented data may be used by other researchers (e.g. in the validation of their prediction models), since it can be downloaded from www.fe.up.pt/~csf/DataCarregado.zip .

This work is focused on the analysis of noise and vibration generated in underground railway tunnels due to train traffic. Specifically, an analysis of noise and vibration generated by train passage in an underground simple tunnel in a homogeneous full-space is presented. In this methodology, a two-and-a-half-dimensional coupled finite element and boundary element method (2.5D FEM-BEM) is used to model soil–structure interaction problems. The noise analysis inside the tunnel is performed using a 2.5D acoustic BEM considering a weak coupling. The method of fundamental solutions (MFS) is used to validate the acoustic BEM methodology. The influence of fastener stiffness on vibration and noise characteristic inside a simple tunnel is investigated.

In this paper, a hybrid experimental/numerical methodology for the assessment of railway-induced ground-borne noise and vibration in buildings based on experimental measurement in the ground surface is presented. This methodology is specifically designed for the prediction of railway-induced vibration in buildings to be constructed close to operative railway infrastructures. A set of virtual forces applied in the ground, as a model of the incident wave field induced by the railway infrastructure, are obtained from vibration experimental measurements in the surface of the ground close to the future building foundation. These virtual forces can be subsequently applied on a model of the building/soil system to obtain a prediction of the vibration that will be induced by the existing railway track to the studied building. In the present work, this methodology is presented and validated numerically by a two-dimensional example and a two-and-a-half-dimensional one. The proposed hybrid model simplifies the usual numerical procedure for these problems, since a model of the railway infrastructure is not longer required. Moreover, it reduces the uncertainty of the prediction due to the use of experimental measurements of the particular site to be studied. In addition, it provides a higher accuracy and flexibility than empirical models based on experimental transmissibility functions between the ground surface and the building. (c) INTER-NOISE 2019 MADRID - 48th International Congress and Exhibition on Noise Control Engineering. All Rights Reserved.

In this paper, a hybrid experimental/numerical methodology for the assessment of railway induced ground-borne noise and vibration in buildings based on experimental measurement in the ground surface is proposed and validated. The application of such approach is focused in the prediction of vibrations and re-radiated noise inside buildings to be constructed nearby existing railway infrastructures. Departing from this presuppose, experimental data about ground-borne vibrations in the free field, i.e., before building construction, can be measured. Based with these experimental data, a numerical model is constructed in order to compute a set of virtual forces applied in the ground that give rise to the same incident wave field induced by the railway infrastructure. These virtual forces are subsequently applied on a model of the building/soil system to obtain a prediction of the vibration that will be induced by the existing railway track to the studied building. In the present work, this methodology is presented and validated numerically by a two-dimensional example. The proposed hybrid model makes the simulation of vibrations inside future buildings close to railway infrastructures easier. Even more relevant, it reduces the uncertainty of the prediction due to the use of experimental measurements of the particular site to be studied.

The use of numerical tools to predict and analyze the dynamic response of buildings exposed to railway traffic is essential to face the continuous challenges motivated by the increasing demand for transportation infrastructures in urban context. Given the complexity of the entire system involved, their experimental validation is an essential step. The existence of a completely characterized experimental test site, where the whole system is considered, from the vibration source (the vehicle-track interaction) to the receiver (the building and its users), allows approaching the problem in a comprehensive and integrated way. Thus, this paper presents an extensive experimental characterization of a structure built next to a railway line, in an experimental test site near Carregado, in Portugal, for which a deep characterization of the geotechnical profile and of the railway track has already been developed and is here summarized. The construction of the structure, exclusively for experimental purposes, allows the in-situ validation of a simplified methodology to deal with soil-structure interaction problems in the context of vibrations induced by railway traffic.

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 vibrat...

When constructing a new railway line, its long length means there are significant financial implications associated with determining the geodynamic ground properties. Therefore, this paper presents recommendations to optimize the efficiency and depth of such a geotechnical site investigation. Firstly, a numerical analysis is performed to investigate the effect of soil layering, soil stiffness and track bending stiffness on critical velocity. It is shown that each of these variables play an important role, however for most practical cases, only the top 8 m of soil is influential. Track dynamics are rarely affected by soil properties at depths below this, meaning this is the maximum required depth of soil investigation. Using this knowledge, a hybrid experimental-analytical methodology is presented, based on a geophysical Spectral Analysis of Surface Waves (SASW) experimental setup to compute the ground dispersion curve and an analytical model to compute the track dispersion curve. The experimental and analytical results are combined directly, to accurately compute the critical velocity. This approach is attractive because: 1) SASW tests are typically accurate to ≈8 m (when using a mobile exciter) thus matching the required depth needed for critical velocity computation, 2) soil property uncertainties are inherently accounted for, 3) the uncertainties associated with SASW inversion are avoided. The approach is attractive when constructing new railway lines and upgrading the speed of existing lines because it can potentially yield site investigation cost savings. In-situ field work is performed to show the practical application of the technique., This research was financially supported by: Project POCI-01-0145-FEDER-007457–CONSTRUCT–Institute of R&D InStructures and Construction funded by FEDER funds through COMPETE2020– Programa Operacional Competitividade e Internacionalização (POCI)–and by national funds through FCT–Fundação para a Ciência e a Tecnologia; Project POCI-01-0145-FEDER-029577–funded by FEDER funds through COMPETE2020 – Programa Operacional Competitividade e Internacionalização (POCI), national funds (PIDDAC) through FCT and the Leverhulme Trust (PLP-2016-270). This work was partially carried out under the framework of In2Track2, a research project of Shift2Rail. The financial support provided by University of Leeds Cheney Award Scheme is also appreciated.

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.

No presente artigo apresenta‐se um estudo numérico sobre a evolução do estado de tensão geomecânico induzido pela passagem de tráfego ferroviário. O modelo numérico proposto é baseado na formulação 2,5D apoiada no MEF‐PML, permitindo a consideração da interação do sistema composto pelo comboio, via‐férrea e maciço de fundação. Para o caso de estudo proposto, as alterações do estado de tensão são sistematizadas sob a forma de trajetórias de tensão. Perante os resultados alcançados é possível reconhecer a grande influência da velocidade de circulação do comboio e da presença de irregularidades na via no comportamento da via‐férrea. Tirando partido dos conhecimentos adquiridos com a realização dos estudos paramétricos referidos, verifica‐se a adequabilidade de um ensaio laboratorial –ensaio torsional com cilindro vazado– na simulação das complexas trajetórias de tensão induzidas no solo de fundação pela passagem do tráfego ferroviário. Os resultados obtidos permitem perspetivar a simulação em laboratório dessa ação, através de um carregamento cíclico, com o objetivo de estudar a acumulação de dano nas amostras. In this paper, a numerical study of the geomechanical stress state evolution induced by the railway traffic is presented. The numerical model is based on a 2.5D formulation with the ability to account for the dynamic train‐track interaction. For the case study, the stress state evolution is systematized in the form of stress paths. The results obtained allow to recognize the great influence of the train speed and the presence of irregularities in the track for the behavior of the railway track. Based on the knowledge acquired during the implementation of previous parametric studies, the adequacy of the hollow cylinder torsional test to simulate the complex stress paths induced in the ground of the traffic railway is evaluated. The results obtained allow to put in perspective the simulation of these loads in laboratory, with the aim of studying the damage accumulation in the specimens.

The dynamic amplification effects of the response due to a moving load on the surface of an elastic solid has been object of research for more than a century. However, if in the beginning of the last century the problem had only theoretical interest, this is no longer true. Indeed, the recent advancements in the rolling stock, which can now reach speeds higher than 500 km/h, brought this kind of problems to the engineering practice, mainly to high speed railway engineering. The present paper approaches this problem focusing on railway engineering. The departing point is the theoretical formulation of the critical speed problem of a moving load on the surface of an elastic solid. From the usage of 2.5D detailed models it was possible to understand the influence of the embankment and track properties on the critical speed. However, to avoid complex numerical models, which are very demanding from the computational point of view, a simplified approach is proposed for the computation of the critical speed of track–embankment–ground systems. The results of the simplified approach are compared to those achieved by detailed methods, also presented in this paper, and the proposed expedite methodology is found to be very accurate.

The growing of railway infrastructures in urban environments demands accurate methods to predict and mitigate potential annoyance of the inhabitants of the surrounding buildings. The present paper aims to contribute to the goal by proposing a numerical model to predict vibrations and reradiated noise due to railway traffic. The model is based on a substructuring approach, where the whole propagation media are considered, from the vibration source (the vehicle–track interaction) to the receiver (the building and its interior acoustic environment). The system track–ground–building is simulated by a 2.5D finite element method–perfectly matched layers (FEM–PML) model, formulated in the frequency-wavenumber domain. The reradiated noise assessment is based on a 2.5D FEM–method of fundamental solutions (MFS) model, where the FEM is used to obtain the structural dynamic response. The structural displacements computed are used as the vibration input for the MFS model in order to assess the acoustic response inside the building's compartments. An application example is presented to assess vibrations and reradiated noise levels inside the building due to railway traffic. This is then followed by a discussion about the potential benefits of the introduction of floating-slab-track systems.

In the last decades, the number of railway projects in urban environment has continuously increased. This rising requires a significant level of knowledge from the scientific and technical communities about the phenomena of generation and propagation of vibrations with emphasis on its interference in nearby buildings and the consequent nuisance of their occupants. In this context, a numerical model to predict vibrations and re-radiated noise in buildings induced by railway traffic is presented. The model is based in a sub-structuring approach, where the whole propagation media is considered, from the vibration source (vehicle-track interaction) to the receiver (building and interior acoustic media). The track-ground-building system is simulated by a 2.5D FEM-PML model, formulated in the frequency - wavenumber domain. The re-radiated noise evaluation is based on a 2.5D FEM-MFS model, where the FEM is used to obtain the structural response. The computed structural displacements are then used as vibration input to the Method of Fundamental Solutions (MFS) model in order to assess the acoustic response in the building’s enclosures. Finally, a parametric-study focused in the evaluation of the influence of a mitigation measure in the reduction of the vibrations and re-radiated noise levels is presented.

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. This work was financially supported by: Project POCI-01-0145-FEDER-007457 - CONSTRUCT - Institute of R&D in Structures and Construction funded by FEDER funds through COMPETE2020 - Programa Operacional Competitividade e Internacionaliza??o (POCI) - and by national funds through FCT - Fundacao para a Ciencia e a Tecnologia: Project PTDC/ECM-COM/1364/2014 and Individual Grant SFRH/BD/101044/2014. Scopus

In this paper, a robust and fast numerical methodology to compute re-radiated noise in underground railway tunnels is proposed. In this study, the noise analysis does not account for the noise radiation from the train wheels, the rest of the rolling stock structure and the aerodynamic noise. The method is based on decoupled approach, where the acoustic and elastodynamic problems are solved separately on the assumption of weak coupling between the two subdomains. Two-and-a-half dimension (2.5D) finite element boundary element (FEM-BEM) is used to analyse the elastodynamic problem. The computation of the re-radiated noise from the vibration of the structure is done with a 2.5D acoustic boundary element method (BEM). The acoustic as well as elastodynamic BEM used in this analysis is based on globally regularized integrals based on singularity subtraction. (c) INTER-NOISE 2019 MADRID - 48th International Congress and Exhibition on Noise Control Engineering. All Rights Reserved.