Articles de revista
http://hdl.handle.net/2117/3363
20200124T17:41:10Z

Experimental and numerical assessment of local resonance phenomena in 3Dprinted acoustic metamaterials
http://hdl.handle.net/2117/174731
Experimental and numerical assessment of local resonance phenomena in 3Dprinted acoustic metamaterials
Roca Cazorla, David; Pàmies Gómez, Teresa; Cante Terán, Juan Carlos; Lloberas Valls, Oriol; Oliver Olivella, Xavier
The so called Locally Resonant Acoustic Metamaterials (LRAM) are a new kind of artificially engineered materials capable of attenuating acoustic waves. As the name suggests, this phenomenon occurs in the vicinity of internal frequencies of the material structure, and can give rise to acoustic bandgaps. One possible way to achieve this is by considering periodic arrangements of a certain topology (unit cell), smaller in size than the characteristic wavelength. In this context, a computational model based on a homogenization framework has been developed from which one can obtain the aforementioned resonance frequencies for a given LRAM unit cell design in the subwavelength regime, which is suitable for lowfrequency applications. Aiming at validating both the proposed numerical model and the local resonance phenomena responsible for the attenuation capabilities of such materials, a 3Dprinted prototype consisting of a plate with a well selected LRAM unit cell design has been built and its acoustic response to normal incident waves in the range between 500 and 2000 Hz has been tested in an impedance tube. The results demonstrate the attenuating capabilities of the proposed design in the targeted frequency range for normal incident sound pressure waves and also establish the proposed formulation as the fundamental base for the computational design of 3Dprinted LRAMbased structures.
20200113T23:08:35Z
Roca Cazorla, David
Pàmies Gómez, Teresa
Cante Terán, Juan Carlos
Lloberas Valls, Oriol
Oliver Olivella, Xavier
The so called Locally Resonant Acoustic Metamaterials (LRAM) are a new kind of artificially engineered materials capable of attenuating acoustic waves. As the name suggests, this phenomenon occurs in the vicinity of internal frequencies of the material structure, and can give rise to acoustic bandgaps. One possible way to achieve this is by considering periodic arrangements of a certain topology (unit cell), smaller in size than the characteristic wavelength. In this context, a computational model based on a homogenization framework has been developed from which one can obtain the aforementioned resonance frequencies for a given LRAM unit cell design in the subwavelength regime, which is suitable for lowfrequency applications. Aiming at validating both the proposed numerical model and the local resonance phenomena responsible for the attenuation capabilities of such materials, a 3Dprinted prototype consisting of a plate with a well selected LRAM unit cell design has been built and its acoustic response to normal incident waves in the range between 500 and 2000 Hz has been tested in an impedance tube. The results demonstrate the attenuating capabilities of the proposed design in the targeted frequency range for normal incident sound pressure waves and also establish the proposed formulation as the fundamental base for the computational design of 3Dprinted LRAMbased structures.

Control of groundborne underground railwayinduced vibration from doubledeck tunnel infrastructures by means of dynamic vibration absorbers
http://hdl.handle.net/2117/174712
Control of groundborne underground railwayinduced vibration from doubledeck tunnel infrastructures by means of dynamic vibration absorbers
Noori, Beshshad; Arcos Villamarín, Robert; Clot Razquin, Arnau; Romeu Garbí, Jordi
The aim of this study is to investigate the efficiency of Dynamic Vibration Absorbers (DVAs) as a vibration abatement solution for railwayinduced vibrations in the framework of a doubledeck circular railway tunnel infrastructure. A previously developed semianalytical model of the tracktunnelground system is employed to calculate the energy flow resulting from a train passby. A methodology for the coupling of a set of longitudinal distributions of DVAs over a railway system is presented as a general approach, as well as its specific application for the case of the doubledeck tunnel model. In the basis of this model, a Genetic Algorithm (GA) is used to obtain the optimal parameters of the DVAs to minimize the vibration energy flow radiated upwards by the tunnel. The parameters of the DVAs set to be optimized are the natural frequency, the viscous damping and their positions. The results show that the DVAs would be an effective countermeasure to address railway induced groundborne vibration as the total energy flowradiated upwards fromthe tunnel can be reduced by an amount between 5.3 dB and 6.6 dB with optimized DVAs depending on the type of the soil and the train speed
20200113T14:24:23Z
Noori, Beshshad
Arcos Villamarín, Robert
Clot Razquin, Arnau
Romeu Garbí, Jordi
The aim of this study is to investigate the efficiency of Dynamic Vibration Absorbers (DVAs) as a vibration abatement solution for railwayinduced vibrations in the framework of a doubledeck circular railway tunnel infrastructure. A previously developed semianalytical model of the tracktunnelground system is employed to calculate the energy flow resulting from a train passby. A methodology for the coupling of a set of longitudinal distributions of DVAs over a railway system is presented as a general approach, as well as its specific application for the case of the doubledeck tunnel model. In the basis of this model, a Genetic Algorithm (GA) is used to obtain the optimal parameters of the DVAs to minimize the vibration energy flow radiated upwards by the tunnel. The parameters of the DVAs set to be optimized are the natural frequency, the viscous damping and their positions. The results show that the DVAs would be an effective countermeasure to address railway induced groundborne vibration as the total energy flowradiated upwards fromthe tunnel can be reduced by an amount between 5.3 dB and 6.6 dB with optimized DVAs depending on the type of the soil and the train speed

A lowcost noise measurement device for noise mapping based on mobile sampling
http://hdl.handle.net/2117/171697
A lowcost noise measurement device for noise mapping based on mobile sampling
Quintero Pérez, Guillermo; Balastegui Manso, Andreu; Romeu Garbí, Jordi
For the production of representative noise maps, a large amount of information is necessary, which includes, among others, onsite measurements of environmental noise. Thus, mobile sampling emerges as a possible solution for the enhancement of data acquisition. The present paper proposes a lowcost noise monitoring device, in order to take georeferenced mobile measurements at each 1/3 octave band (63¿Hz–10¿kHz). The implementation and accuracy tests of the equipment are presented. It is found, under laboratory and field tests, that the device measurement values are around 0.5¿dB of those obtained with a Class 1 sound level meter for and around 1¿dB for 1/3 octave band. Furthermore, a set of mobile measurements taken suggest that it is actually possible to perform the mobile sampling, which would improve the spatiotemporal granularity of noise measurements without compromising the accuracy, although certain requirements should be fulfilled to ensure representativeness
20191105T12:25:38Z
Quintero Pérez, Guillermo
Balastegui Manso, Andreu
Romeu Garbí, Jordi
For the production of representative noise maps, a large amount of information is necessary, which includes, among others, onsite measurements of environmental noise. Thus, mobile sampling emerges as a possible solution for the enhancement of data acquisition. The present paper proposes a lowcost noise monitoring device, in order to take georeferenced mobile measurements at each 1/3 octave band (63¿Hz–10¿kHz). The implementation and accuracy tests of the equipment are presented. It is found, under laboratory and field tests, that the device measurement values are around 0.5¿dB of those obtained with a Class 1 sound level meter for and around 1¿dB for 1/3 octave band. Furthermore, a set of mobile measurements taken suggest that it is actually possible to perform the mobile sampling, which would improve the spatiotemporal granularity of noise measurements without compromising the accuracy, although certain requirements should be fulfilled to ensure representativeness

Statistical requirements for noise mapping based on mobile measurements using bikes
http://hdl.handle.net/2117/171691
Statistical requirements for noise mapping based on mobile measurements using bikes
Quintero Pérez, Guillermo; Aumond, Pierre; Can, A.; Balastegui Manso, Andreu; Romeu Garbí, Jordi
This research presents a modeling framework that allows checking the statistical requirements for producing noise maps based on mobile measurements. First, a sound field of reference is created based on a microsimulation traffic modeling coupled with acoustic modeling, which outputs sound levels each second on a grid of receivers. The aggregated indicators (LAeq) calculated from this sound field serve then as reference. Mobile targets performing measurements evolve within the simulation, aiming to estimate these indicators. The difference between the reference noise map and the one generated by the moving receivers, characterized by the Root Mean Square Error (RMSE), is computed for different aggregation radius of mobile receivers, and as a function of the number of passesby and to the distance to its nearest cross street. It is observed that the mobile sampling is actually possible and the RMSE can be reduced by setting an optimal aggregation radius and a minimum number of passesby. With the optimal parameters, 95% of the mobile samples fall within an estimation error interval of [3.0, 2.2] dBA from the reference. It is also shown that the distance to the nearest cross street affects the estimation error depending on the traffic flow, producing a RMSE greater than 2 dB for distances lower than 30 m
20191105T11:18:57Z
Quintero Pérez, Guillermo
Aumond, Pierre
Can, A.
Balastegui Manso, Andreu
Romeu Garbí, Jordi
This research presents a modeling framework that allows checking the statistical requirements for producing noise maps based on mobile measurements. First, a sound field of reference is created based on a microsimulation traffic modeling coupled with acoustic modeling, which outputs sound levels each second on a grid of receivers. The aggregated indicators (LAeq) calculated from this sound field serve then as reference. Mobile targets performing measurements evolve within the simulation, aiming to estimate these indicators. The difference between the reference noise map and the one generated by the moving receivers, characterized by the Root Mean Square Error (RMSE), is computed for different aggregation radius of mobile receivers, and as a function of the number of passesby and to the distance to its nearest cross street. It is observed that the mobile sampling is actually possible and the RMSE can be reduced by setting an optimal aggregation radius and a minimum number of passesby. With the optimal parameters, 95% of the mobile samples fall within an estimation error interval of [3.0, 2.2] dBA from the reference. It is also shown that the distance to the nearest cross street affects the estimation error depending on the traffic flow, producing a RMSE greater than 2 dB for distances lower than 30 m

The coupled effects of bending and torsional flexural modes of a highspeed train car body on its vertical ride quality
http://hdl.handle.net/2117/168136
The coupled effects of bending and torsional flexural modes of a highspeed train car body on its vertical ride quality
Bokaeian, Vahid; Rezvani, Mohammad A.; Arcos Villamarín, Robert
This study is focused on the effects of bending and torsional flexural modes of the car body on the ride quality index of a highspeed train vehicle. The Euler–Bernoulli beam model is used to extract an analytical model for a highspeed train vehicle car body in order to investigate its bending and torsional flexural vibrations. The rigid model includes a car body, two bogie frames, and four wheelsets such that, each mass has three degrees of freedom including vertical displacement, pitch motion, and roll motion. The results obtained with the proposed analytical model are compared with experimental measurements of the car body response of a Shinkansen highspeed train. Moreover, it is determined that the bending and torsional flexural modes have significant effects on the vertical acceleration of the car body, particularly in the 9–15¿Hz frequency range. Furthermore, the ride quality index is calculated according to the EN 12299 standard and it is shown that the faster the train the more affected is the ride quality by the flexural modes. In addition, the effect of coherence between two rail irregularities (the right and the left rails) on the results of the simulation is investigated. The results conclude that if the irregularities are completely correlated the torsional flexural mode of the car body does not appear in the response. Also, the first bending flexural mode in such cases is more excited compared with the partially correlated or uncorrelated rail irregularities. Therefore, the ride quality index in completely correlated cases is higher than other cases
20190912T10:08:54Z
Bokaeian, Vahid
Rezvani, Mohammad A.
Arcos Villamarín, Robert
This study is focused on the effects of bending and torsional flexural modes of the car body on the ride quality index of a highspeed train vehicle. The Euler–Bernoulli beam model is used to extract an analytical model for a highspeed train vehicle car body in order to investigate its bending and torsional flexural vibrations. The rigid model includes a car body, two bogie frames, and four wheelsets such that, each mass has three degrees of freedom including vertical displacement, pitch motion, and roll motion. The results obtained with the proposed analytical model are compared with experimental measurements of the car body response of a Shinkansen highspeed train. Moreover, it is determined that the bending and torsional flexural modes have significant effects on the vertical acceleration of the car body, particularly in the 9–15¿Hz frequency range. Furthermore, the ride quality index is calculated according to the EN 12299 standard and it is shown that the faster the train the more affected is the ride quality by the flexural modes. In addition, the effect of coherence between two rail irregularities (the right and the left rails) on the results of the simulation is investigated. The results conclude that if the irregularities are completely correlated the torsional flexural mode of the car body does not appear in the response. Also, the first bending flexural mode in such cases is more excited compared with the partially correlated or uncorrelated rail irregularities. Therefore, the ride quality index in completely correlated cases is higher than other cases

A methodology based on sructural finite element MethodBoundary element method and acoustic boundary element method models in 2.5D for the prediction of reradiated noise in RailwayInduced GroundBorne vibration problems
http://hdl.handle.net/2117/133400
A methodology based on sructural finite element MethodBoundary element method and acoustic boundary element method models in 2.5D for the prediction of reradiated noise in RailwayInduced GroundBorne vibration problems
Ghangale, Dhananjay; Colaço, Aires; Alves Costa, Pedro; Arcos Villamarín, Robert
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 fullspace is presented. In this methodology, a twoandahalfdimensional coupled finite element and boundary element method (2.5D FEMBEM) 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.
20190523T17:25:08Z
Ghangale, Dhananjay
Colaço, Aires
Alves Costa, Pedro
Arcos Villamarín, Robert
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 fullspace is presented. In this methodology, a twoandahalfdimensional coupled finite element and boundary element method (2.5D FEMBEM) 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.

A method based on 3D stiffness matrices in Cartesian coordinates for computation of 2.5D elastodynamic Green's functions of layered halfspaces
http://hdl.handle.net/2117/128005
A method based on 3D stiffness matrices in Cartesian coordinates for computation of 2.5D elastodynamic Green's functions of layered halfspaces
Noori, Behshad; Arcos Villamarín, Robert; Clot, Arnau; Romeu Garbí, Jordi
This article elaborates on an extension to the classical stiffness matrix method to obtain the Green's functions for twoandahalf dimensional (2.5D) elastodynamic problems in homogeneous and horizontally layered halfspaces. Exact expressions for the threedimensional (3D) stiffness matrix method for isotropic layered media in Cartesian coordinates are used to determine the stiffness matrices for a system of horizontal layers underlain by an elastic half–space. In the absence of interfaces, virtual interfaces are considered at the positions of external loads. The analytic continuation is used to find the displacements at any receiver point placed within a layer. The responses of a horizontally layered halfspace subjected to a unit harmonic load obtained using the present method are compared with those calculated using a wellestablished methodology, achieving good agreement
20190131T11:08:04Z
Noori, Behshad
Arcos Villamarín, Robert
Clot, Arnau
Romeu Garbí, Jordi
This article elaborates on an extension to the classical stiffness matrix method to obtain the Green's functions for twoandahalf dimensional (2.5D) elastodynamic problems in homogeneous and horizontally layered halfspaces. Exact expressions for the threedimensional (3D) stiffness matrix method for isotropic layered media in Cartesian coordinates are used to determine the stiffness matrices for a system of horizontal layers underlain by an elastic half–space. In the absence of interfaces, virtual interfaces are considered at the positions of external loads. The analytic continuation is used to find the displacements at any receiver point placed within a layer. The responses of a horizontally layered halfspace subjected to a unit harmonic load obtained using the present method are compared with those calculated using a wellestablished methodology, achieving good agreement

Temporal and spatial stratification for the estimation of nocturnal longterm noise levels
http://hdl.handle.net/2117/127206
Temporal and spatial stratification for the estimation of nocturnal longterm noise levels
Quintero, G.; Romeu Garbí, Jordi; Balastegui Manso, Andreu
Noise pollution in cities is mainly caused by the vehicular traffic but, depending on the place under assessment, it could be affected by the land use. For noise assessment and strategic noise mapping, the night period equivalent level (), which evaluates sleep disturbance, is one of the requirements of the European Directive 2002/49/EC to be presented for the equivalent time of one year. This research aims to find the influence of the land use in the weekdays stratification to improve the accuracy of the longterm noise level estimation for the night period. It is found that depending on the land use of the place under assessment, the weekdays temporal and spatial stratification could be affected by leisure activities. From a statistical analysis based on a clustering procedure of samples in 19 points, it is observed that both, temporal and spatial stratification depend on the intensity of the surrounding leisure activity, and not on traffic. Following these stratification criteria, a sampling method is presented that reduces by 47% the number of days needed to estimate the annual levels with respect to random sampling
20190118T13:06:41Z
Quintero, G.
Romeu Garbí, Jordi
Balastegui Manso, Andreu
Noise pollution in cities is mainly caused by the vehicular traffic but, depending on the place under assessment, it could be affected by the land use. For noise assessment and strategic noise mapping, the night period equivalent level (), which evaluates sleep disturbance, is one of the requirements of the European Directive 2002/49/EC to be presented for the equivalent time of one year. This research aims to find the influence of the land use in the weekdays stratification to improve the accuracy of the longterm noise level estimation for the night period. It is found that depending on the land use of the place under assessment, the weekdays temporal and spatial stratification could be affected by leisure activities. From a statistical analysis based on a clustering procedure of samples in 19 points, it is observed that both, temporal and spatial stratification depend on the intensity of the surrounding leisure activity, and not on traffic. Following these stratification criteria, a sampling method is presented that reduces by 47% the number of days needed to estimate the annual levels with respect to random sampling

Annual traffic noise levels estimation based on temporal stratification
http://hdl.handle.net/2117/111392
Annual traffic noise levels estimation based on temporal stratification
Quintero, G.; Balastegui Manso, Andreu; Romeu Garbí, Jordi
This paper proposes a temporal sampling strategy that increases the accuracy of longterm noise level estimation and allows to establish the estimation error according to the number of sampled days. Days of the week are stratified into working days and weekend days. This research shows how to use measurements of Leq on working days to estimate the corresponding values for weekend days. This is possible because working days have higher noise levels and less variability than weekend days. The improvement in accuracy allows for a reduction in the number of required sampled days compared to taking samples randomly, which would help to reduce the uncertainty in environmental noise assessment. As a reference, to obtain a 90% confidence interval of ±1 dB for Lday, the proposed sampling strategy reduces the required measurement days by more than 38%. For LDEN, the reduction is close to 18% of the total number of days. The proposed strategy could be adapted to different environments by simply changing a few parameters.
© 2017. This version is made available under the CCBYNCND 4.0 license http://creativecommons.org/licenses/byncnd/4.0/
20171130T15:50:29Z
Quintero, G.
Balastegui Manso, Andreu
Romeu Garbí, Jordi
This paper proposes a temporal sampling strategy that increases the accuracy of longterm noise level estimation and allows to establish the estimation error according to the number of sampled days. Days of the week are stratified into working days and weekend days. This research shows how to use measurements of Leq on working days to estimate the corresponding values for weekend days. This is possible because working days have higher noise levels and less variability than weekend days. The improvement in accuracy allows for a reduction in the number of required sampled days compared to taking samples randomly, which would help to reduce the uncertainty in environmental noise assessment. As a reference, to obtain a 90% confidence interval of ±1 dB for Lday, the proposed sampling strategy reduces the required measurement days by more than 38%. For LDEN, the reduction is close to 18% of the total number of days. The proposed strategy could be adapted to different environments by simply changing a few parameters.

Efficient threedimensional buildingsoil model for the prediction of groundborne vibrations in buildings
http://hdl.handle.net/2117/105664
Efficient threedimensional buildingsoil model for the prediction of groundborne vibrations in buildings
Clot Razquin, Arnau; Arcos Villamarín, Robert; Romeu Garbí, Jordi
This paper proposes a new efficient model for the prediction of lowamplitude groundborne vibrations in buildings. The model takes into account the threedimensional nature of the building structure by analytical and semianalytical means, making it ideal for performing parametric studies or largescale vibrations predictions. Its formulation assumes that the principal component in floor vibrations is the vertical one and assumes that the vibrations are transmitted to the various floors through the building columns. The correctness of the model is tested by comparing, in two 3story building examples, its results with those obtained using a numerical model. Results regarding the isolation efficiency of implementing a thicker lower floor or columns with a larger cross section are also presented. The buildingsoil coupling is formulated considering piled foundations in a stratified soil. To ensure the computational efficiency of the calculations, the piles’ response to an incident wavefield is modeled considering the Novak pile model for a layered halfspace. Finally, a study of the importance of the soil mechanical parameters in the considered problem is conducted using the buildingsoil coupled model.
20170620T12:09:37Z
Clot Razquin, Arnau
Arcos Villamarín, Robert
Romeu Garbí, Jordi
This paper proposes a new efficient model for the prediction of lowamplitude groundborne vibrations in buildings. The model takes into account the threedimensional nature of the building structure by analytical and semianalytical means, making it ideal for performing parametric studies or largescale vibrations predictions. Its formulation assumes that the principal component in floor vibrations is the vertical one and assumes that the vibrations are transmitted to the various floors through the building columns. The correctness of the model is tested by comparing, in two 3story building examples, its results with those obtained using a numerical model. Results regarding the isolation efficiency of implementing a thicker lower floor or columns with a larger cross section are also presented. The buildingsoil coupling is formulated considering piled foundations in a stratified soil. To ensure the computational efficiency of the calculations, the piles’ response to an incident wavefield is modeled considering the Novak pile model for a layered halfspace. Finally, a study of the importance of the soil mechanical parameters in the considered problem is conducted using the buildingsoil coupled model.