This paper presents a comparison between the vibration energy flow radiated by a double-deck tunnel and the one radiated by a simple tunnel when both are excited by constant or by harmonic moving loads. For both cases, the radiated energy is computed using a three-dimensional semi-analytical model of the system. The total energy radiated upwards is presented for a wide range of load speeds, when a constant moving load is considered, and for a wide range of excitation frequencies, when the excitation is a harmonic moving load. Significant differences have been obtained, first, for constant loads moving at very high speeds and, second, for harmonic loads moving at typical speeds for underground trains.
In this paper, a methodology for the experimental evaluation of mechanical vibration frequency response functions in the framework of groundbourne railway-induced and construction-induced vibration predictions is presented. This methodology is based on a device specifically designed for the excitation of railway superstructures. The device can be used also to excite the ground with the aim of obtaining ground/building frequency response functions. The resulting frequency response functions can be used to feed prediction empirical models with specific in situ results or to characterize the system by performing an inversion process over a theoretical model of it, among other applications. Two examples of this methodology applied for the experimental determination of frequency response functions and subsequent system characterization are presented.
In the present study, dynamic vibration absorber (DVA) has been introduced as an innovative countermeasure in the field of railway-induced vibration. The Pipe-in-Pipe (PiP) model and Green's functions for a two-and-a-half dimensional (2.5D) elastodynamic problem in a full- and half-space have been employed to find the response of the tunnel embedded in a homogeneous half-space due to a harmonic load. DVAs have been coupled to the tunnel interior surface. The effectiveness of DVAs depends on the mass, damping ratio, natural frequency and their distribution. Therefore, an optimization algorithm has been developed to find the optimum parameters of the DVAs, which are those that minimize the vibration levels at the ground surface. Evaluating the efficiency of the optimal DVAs shows that they are an efficient countermeasure to mitigate underground railway-induced vibration.
Double-deck tunnels are an innovative tunnel design that has been recently implemented in some underground railways and metro lines worldwide. However, due to the complexity of this type of structures, its dynamic response has not yet been fully comprehended. This lack of understanding complicates the design of efficient vibration isolation countermeasures for them. Therefore, proper models for predicting the vibration impact of double-deck tunnels are highly needed. The aim of this paper is to present, on the one hand, an efficient model of a railway superstructure implemented in a double-deck tunnel and, on the other, to study how the vibration impact of this structure is affected by the addition of an elastomeric mat between the interior floor-tunnel contact and by modifications of the rail pads stiffness and damping values. In both cases, the results are presented in terms of the energy flow radiated upwards by the structure when harmonic moving loads circulate along the rails.
La reducción activa de ruido transmitido a través de una apertura se investiga mediante un modelo
teórico. El campo primario se compone de una onda plana que incide sobre una apertura rectangular situada en
una pared infinita de grosor despreciable. El sonido radiado por la apertura se calcula a partir de la ecuación de
radiación de Rayleigh una vez se han aplicado las condiciones de continuidad de presión y velocidad de partícula
en la apertura. El modelo propuesto se compara con un modelo BEM del mismo problema con objeto de su
validación. Una vez validado, la aplicación del control activo se realiza mediante la inclusión de una fuente
secundaria cercana a la apertura que por superposición de campos acústicos minimiza el sonido transmitido en la
región de radiación. Se presentan resultados de atenuación respecto a la frecuencia y dimensión de la apertura.
RECYTRACK es un proyecto de investigación
subvencionado por la Comisión Europea a
través de la convocatoria LIFE+ 2010 cuyo objetivo es demostrar los beneficios
medioambientales y técnicos de la implementación de un material elastomérico respetuoso con el medio ambiente desarrollado a partir de neumáticos fuera de uso mezclados con resina para
AV Ingenieros, junto con el LEAM, lleva a cabo el estudio del comportamiento vibratorio de dicho material, que será aplicado en forma de manta bajo balasto y tacos aislados para superestructura en losa de hormigón. En este artículo se presenta el diseño vibratorio de los productos elastoméricos, realizado mediante un modelo analítico, así como la caracterización
del material en laboratorio a alta frecuencia
Cardona, J.; Clot, A.; Arcos, R.; Torres, R. Congreso Español de Acústica, Encuentro Ibérico de Acústica, EAA European Symposium on Environmental Acoustics and Noise Mapping p. 941-948 Data de presentació: 2014-10-30 Presentació treball a congrés
VIBRO-IMPACT is an investigation project co-funded by the Spanish Centre for Industrial Technological Development, CDTI, which aim is to develop a model for the prediction of the vibration induced in near buildings due to urban public works.
To do so, constructive processes and public work machines that generate greater vibration levels are identified and experimentally characterized. Then, three analytical vibration prediction models are developed: a vibration generation model for each kind of source, a general analytical soil vibration propagation model and a building dynamic model coupled to the previous one.
Finally, a specific experimental methodology to model unique buildings is developed. A self-developed vibration excitation device is used to synthesise the vibration emission of the previously identified urban public work sources.
VIBRO-IMPACT es un proyecto de investigación co-financiado por el Centro para el Desarrollo Tecnológico Industrial, CDTI, cuyo objetivo es el desarrollo de un modelo para la predicción, en fase de proyecto, de las vibraciones inducidas en las viviendas debido a las máquinas y procesos constructivos de las obras públicas urbanas.
Para ello, se identifican las máquinas y procesos constructivos que generan mayores niveles de vibración y se desarrollan tres modelos predictivos: un modelo analítico de la generación de vibraciones de dichas fuentes, un modelo analítico de propagación de las vibraciones a través del terreno y un modelo analítico del comportamiento dinámico de los edificios acoplado al de propagación por el terreno.
Finalmente, se propone también una metodología experimental particular para el estudio de edificios singulares, en la que las vibraciones se generan mediante un excitador de desarrollo propio que sintetiza la emisión vibratoria de las fuentes identificadas presentes en la obra pública.
This paper presents an experimental work on active control of sound transmission through a restricted opening bottom hinged window. The main goal of the work is to demonstrate the feasibility of the active technique to limit the loss of attenuation due to the aperture of windows, and its application to aircraft fly-over incident noise. The experimental window is placed in an exposed facade of a dwelling close to an airport and subject to fly-by aircraft noise. The active control is configured to cancel the pressure at the aperture using a single-input single-output feedforward adaptive system. As a result, a reduction of sound transmission is achieved with low power consumption. In global terms, an increase of almost 3 dB of transmission loss (with respect to the partially opened window insulation values) in the low frequency range (below 160 Hz and according to the National Danish Method for evaluating low frequency noise) is demonstrated, which is equivalent to a reduction of 50% in the loss of insulation caused by opening the window. (C) 2014 Elsevier Ltd. All rights reserved.
The use of elastomeric particles obtained from old tires to produce anti-vibration mats to reduce vibrations in railways is studied. In the first part of this work a numerical simulation for dimensioning the element has been performed. The behavior for a wavy surface was deducted obtaining good approximation to the empirical results. In the second part the methodology used to assess the Insertion Loss, IL, provided by the anti-vibration system is described. The analytical superstructure/ground model developed within the frame of the project is presented. The model is based on an elementary superstructure model with no elastomeric material and is conveniently modified to introduce an under ballast mat. Finally the study shows the validation of the mechanical behavior of prototype mats under dynamic efforts according to standards [1-6]. The results show that the behavior of crushed rubber is suitable to be used as anti-vibration systems
Martin, S.R.; Genesca, M.; Romeu, J.; Arcos, R. IEEE transactions on aerospace and electronic systems Vol. 50, num. 2, p. 1330-1346 DOI: 10.1109/TAES.2013.120176 Data de publicació: 2014-04-01 Article en revista
A passive acoustic method to locate moving sound sources is applied to maneuvering aircraft. The advantages of the method are that it is suitable for all kinds of aircraft, not only propeller-driven, and is not restricted to low height above the ground. Its applicability could be, for instance, to supplement aircraft noise monitoring systems or to supervise small airports' activities. The method is based on the relation between the relative Doppler effect observed from a set of at least seven microphone receivers, distributed in the airport surroundings, and the aircraft position and speed. The method requires knowledge of the position of the aircraft at the start of takeoff. The ambiguity function is used to calculate the relative Doppler stretch of the spectrum of the sound between pairs of microphones. The results of applying the ambiguity function are the inputs to a system of equations that relates the aircraft position and speed to the relative Doppler frequency stretches. This system of equations is solved using a genetic algorithm. The performance of the method was tested by computer simulation. The results showed that the location errors are of the same order of magnitude as the size of an average aircraft, even if the takeoff position is not accurately known.
This paper uses an analytical model of sound transmission through an aperture for the study of the performance of an active control of sound inside the enclosure to prevent the transmission of sound through an aperture placed in the enclosure wall, by comparing different active control strategies for the particular case of the low modal sound field. The results indicate that a global active control inside the enclosure is not enough to reduce the sound transmission through an aperture, but also that a practical approach consists of cancelling the pressure at the center of the plane of the aperture, thus ensuring satisfactory results.
Aquesta tesis presenta un model dinàmic tridimensional d¿un túnel circular de dos pisos situat en el si d¿un espai infinit. El model fa ús del mètode de la receptància per a obtenir la resposta de l¿estructura completa a partir de la resposta de les seves parts. Els subsistemes considerats són, per una banda, el terra interior, i per l¿altra, el sistema acoblat túnel-terreny. El comportament dinàmic del primer es modelitza mitjançant la teoria clàssica de placa prima i el model Pipe-in-Pipe és l¿escollit per a descriure el segon. Com que el model proposat assumeix que el sistema és geomètricament invariant en la direcció de circulació dels trens, l¿acoblament dels subsistemes es pot realitzar en el domini nombre d¿ona-freqüència. Un cop el model ha estat formulat, es detallen els principals aspectes a tenir en compte en la seva computació numèrica i s¿interpreten els resultats obtinguts. La resposta d¿un túnel de dos pisos tant a una excitació dinàmica com a una de quasiestàtica es comparada a la resposta obtinguda en el cas d¿un túnel d'un únic pis. La primera comparativa es realitza mitjançant un estudi del flux de potència radiat per ambdues estructures sota l¿aplicació d¿una càrrega harmònica lineal. Les principals diferències entre les magnituds i els patrons de radiació són detallades i discutides. La segona comparativa es realitza calculant el flux total d¿energia que travessa una certa superfície del terreny quan una càrrega que es desplaça a velocitat constant es aplicada sobre ambdós túnels. La comparativa entre les respostes dels tunels es realitza per un ampli rang de velocitats. Finalment, es presenta un model complert de via-túnel-terreny obtingut a partir de l¿acoblament d¿un model de superestructura al model de túnel prèviament desenvolupat.
This thesis presents a three-dimensional dynamic model of a double-deck circular tunnel embedded in a full-space. The model uses the receptance method to obtain the response of the complete structure from the response of its parts. The considered subsystems are the interior floor and the tunnel-soil coupled system. The classical thin plate theory is considered to represent the behaviour of the first and the Pipe in Pipe model is chosen to describe the second. Because the complete model is assumed to be geometrically invariant in the train circulation direction, the coupling of both systems is performed in the wavenumber-frequency domain. After the model formulation, some important issues about its numerical computation are detailed and the obtained results are discussed. The response of a double-deck tunnel to a dynamic and to a quasistatic excitation is compared to the response obtained for a simple tunnel. The first comparison is done performing a power flow study of both tunnel structures when a harmonic line load is applied on them. The main differences between their radiation magnitudes and patterns are identified and discussed. The second comparison is done calculating the total amount of energy crossing a certain surface when a static load moving at a constant speed is considered. Results for a wide range of load speeds and radial distances are presented. A complete track-tunnel-soil model is finally obtained coupling a superstructure model to the interior floor model previously presented.
In the context of the developing of a numerically efficient model of railway induced ground vibrations, the problem of an infinite, longitudinally-varying and harmonic strip load acting on the surface of a viscoelastic half-space is reformulated in order to improve its numerical evaluation. On one hand, the static integrands of this specific problem are modified and introduced into the original integrands to reduce their spectral content at high wavenumbers, saving computational time needed for the numerical integration. On the other hand, a change of variable is applied on the displacements integral solutions resulting on frequency independent integrands. These formulae allow to obtain the displacement solution in the complete x-y-ω field easier and, mostly, faster
The purpose of the present investigation is to obtain the mean power flow radiated by a double-deck circular tunnel and compares it to the one radiated by a simple circular tunnel. To achieve this, a harmonic line load is applied on the interior floor of the
first one and at the bottom of the second one.
For the double-deck tunnel, a new analytical model based on the receptance method is developed. The proposed model describes the dynamics of the interior floor using the thin plate theory and considers the
Pipe in Pipe (PiP) model to describe the tunnel and soil coupled system. Plain strain conditions are assumed for both systems and conservative coupling is considered between them. Numerical results show significant differences between the power flow radiated by both tunnels, with the one radiated by
the double-deck tunnel reaching much higher values.
The performance of an active control system in global control of enclosed sound fields depends largely on the localization of the error sensors, among other factors. In this paper a modified cost function is proposed in order to guarantee the maximum attenuation that can be produced by a set of secondary sources in the case of an harmonically excited sound field. The cost function is modified in order to drive the error signal to the value corresponding to the optimally attenuated sound field, instead of minimizing the squared pressure. To evaluate the performance of the proposed control system, its robustness against unstructured error is also investigated using a set of intensive calculations. Following this approach, the sensors can be located anywhere and the optimal attenuation is reached using an equal number of error sensors and secondary sources. The results also suggest that the greater the number of error sensors than secondary sources the more robust the control system is. This behavior holds for both the usual strategy of minimizing the squared pressure and the approach presented in this paper. However, the latter strategy is more robust than the traditional approach of minimizing the squared pressures and its robustness does not depend on the location of the error sensors. Thus, as a main conclusion, the use of the new cost function leads to a guaranteed efficiency and a more robust control system and gives absolute freedom in selecting the location of the error sensors.
Este artículo presenta un trabajo experimental basado en el control activo de la transmisión del sonido mediante la apertura restringida de una ventana abatible inferior. se desea demostrar que la viabilidad de la técnica activa para limitar la pérdida de atenuación debida a la abertura de ventanas y su aplicación sobre el ruido que produce el sobrevuelo de aeronaves. la ventana experimental se coloca en la fachada de una vivienda cerca de un aeropuerto que esté sujeta a
dicho ruido mientras que el control activo está configurado para cancelar la presión en la abertura utilizando un sistema adaptativo de
alimentación directa de entrada y salida única.
The prediction of vibration levels near underground trains is of growing importance for newly constructed infrastructures in cities. Before construction, preliminary studies of vibration impact need to be undertaken in order to identify the buildings that may be affected based on vibration contamination laws and modify the railway line or the type of superstructure if necessary. These studies need fast and economic models due to the large areas they need to cover. The present study aims at predicting the vibration impact for the new Line 9 of Barcelona Underground which is 48 km long. The solution presented is a fast pre-calculated 2D FEM model which is run once for a set of different soil types and tunnel depths, obtaining sets of surface vibration levels. Interpolating between the depths and distances of the tabulated results can be used as a very fast model for prediction. The model is calibrated with measurements in the same conditions (rolling stock and superstructure) as those expected in Line 9 and offers an accuracy not far from current 2.5D and 3D models.
Genesca, M.; Romeu, J.; Arcos, R.; Martin, S.R. Transportation research. Part D, transport and environment Vol. 18, p. 70-77 DOI: 10.1016/j.trd.2012.09.002 Data de publicació: 2013-01 Article en revista
Two analytical modifications of the original viscoelastic time-harmonic Lamb’s problem
expressions are presented with the aim of improving their numerical integration efficiency.
Firstly, a new change of variable in the Lamb’s problem integrands is proposed, which
allows a standardization of the integration sampling vector and a complete spatialfrequency
field solution after performing only one numerical integration/transformation.
Secondly, the Lamb’s problem static integrands are modified and introduced into the
original integrands to reduce their spectral content at high wavenumbers and, therefore,
the sampling vector lengths needed to avoid aliasing.
RECYTRACK is a 3.5 year project granted by the European Union through LIFE+ 2010 program. The overall objective of the project is to demonstrate the environmental benefits and technical and economic feasibility of the implementation of an elastomeric eco-friendly material made of end-of-life tires with resin for railway applications. Within the consortium, AV Ingenieros jointly with LEAM, carries out the study of the vibration behavior of the eco-friendly material, which will be applied as a mat for ballasted tracks as well as an isolated block system for slab tracks. Firstly, an analytical model capable to characterize the eco-friendly material vibration behavior is under development. Subsequently, and after the implementation of the eco-friendly solutions in real railway infrastructures, its vibration behavior will be measured and validated through in situ measurements during the infrastructure commercial exploitation
RECYTRACK is a 3.5 year project granted by the European Union through LIFE+ 2010
program. The overall objective of the project is to demonstrate the environmental benefits and technical and economic feasibility of the implementation of an elastomeric eco-friendly material made of end-of-life tires with resin for railway applications.
Within the consortium, AV Ingenieros jointly with LEAM, carries out the study of the
vibration behavior of the eco-friendly material, which will be applied as a mat for ballasted tracks as well as an isolated block system for slab tracks. Firstly, an analytical model capable to characterize the eco-friendly material vibration behavior is under development.
Subsequently, and after the implementation of the eco-friendly solutions in real railway
infrastructures, its vibration behavior will be measured and validated through in situ
measurements during the infrastructure commercial exploitation.
This thesis focuses on the development of an analytical model for the generation and
propagation parts of a global model of ground induced vibrations to be used in preliminary
assessment studies for the case of at-grade railway infrastructures. The model is
designed prioritising its speed, simplicity and usability ahead its accuracy modelling the
real railway system. This model takes into account the subgrade as a viscoelastic and
homogeneous half-space, the superstructure as a 2-layer supporting model and the vehicle
as 1DOF system. With the aim of simplify the model, the superstructure/subgrade
interaction is studied in terms of the wheel/rail contact dynamics, bounding in what
cases this interaction can be neglected. The adaptation of this model when a far eld
semi-analytical model is desired to be used as the propagation model is fully developed,
by means of the dimensioning of the near eld and far eld regions.
Arcos, R.; Romeu, J.; Balastegui, A.; Pàmies, T. Soil dynamics and earthquake engineering (1984) Vol. 31, num. 7, p. 1072-1074 DOI: 10.1016/j.soildyn.2011.02.004 Data de publicació: 2011 Article en revista
Due to the increasing number and kilometres of new railways lines, either high speed railway lines or commuter lines, as well as the increasing in human sensitivity versus ground-borne vibration generated for this mean of transport, a sustained growth in complaints due to the annoyance caused by railway vibrations has been detected.
In order to predict the field vibrations caused by new railway lines in the project stage, which will be useful to design appropriate countermeasures, in the present work a ground-borne vibration model for rail systems at-grade developed by the authors is validated with experimental measurements in an existing commuter railway line. It checked that this model is a very useful tool to predict the vibration field that will be caused by a railway infrastructure in the planning stage of the project.
The prediction of vibration impact remains as a complex challenge for designers of new railway infrastructures. Due to the large quantity of parameters involved in the generation, transmission and reception of the vibration waves, it would be necessary to develop a complete study for each potential receiver, which would include: source, soil and building characterization,
infrastructure vibration behaviour modelling and, finally, countermeasures influence prediction.
This process can turn out to be very costly in terms of both time and money. Therefore, it is usually done only for areas very likely to suffer high vibration levels or for high sensitive buildings (hospital, educational).
The CATdBTren project, which has been awarded with R&D funding from the Catalonia
Government, is aimed to develop a new prediction tool for evaluating the vibration impact from new railway infrastructures as well as to develop new types of fastening systems having high vibration isolation properties. That tool is intended to be user-friendly and to produce results with
average accuracy, so it still will be required detailed studies of problematic areas.
In this sense, the software will model the contact forces caused by high-speed, conventional and underground rolling stock. Moreover, it will model the infrastructure’s vibration transmission behaviour, ground vibration propagation, terrain-foundation coupling and building vibration
mechanism. The CATdBTren prediction tool will be also capable of estimating the influence of the rolling stock, rail and wheel roughness, fastening system, substructure, soil vibration propagation properties and building characteristics, all in the final vibration impact.
Many studies have been focused on the development of vibration source models, which
comprise both the force applied on the track top and the vibration behaviour of the fixation system. Numerous researchers model the interaction between wheel and rail as a constant load moving along the track. Other authors consider a combination of harmonic and non-harmonic moving axle loads. Whereas most of these models are intended to validate time-domain vibration results, they become useless for predicting the frequency-domain vibration impact far from the track, data which is required in order to asses the fulfilment implied by most of the national regulations.
In this work, two source models are presented and described. The first model comprises a series of empirical-statistical models, based on vibration measurements carried out in rail tracks.
These models allow predicting the mean frequency-dependent applied force by high-speed, conventional and underground rolling stock. The second model consists in an analyticdeterministic approach based on the theoretical model of the wheel-rail deformation. This deformation is used to obtain the wheel-rail contact force trough the Hertz’s Theory of mechanical contacts. The model includes the superstructure motion, considering the rail as a
Bernoulli-Euler beam, the sleepers as a punctual mass, and the pad, ballast and ground impedances.
These source models will be included in the prediction tool for evaluating the vibration impact for new railway infrastructures, which is being developed within the CATdBTren project. This project has been awarded a R&D funding from the Catalonian Governmen.