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In this paper, a novel hybrid meshless approach that combines the singular boundary method (SBM) and the method of fundamental solutions (MFS) to deal with two-dimensional (2D) exterior acoustic wave propagation problems is proposed and studied. The methodology is particularly devised to solve problems with complex boundary geometries containing geometric singularities such as corners and sharp edges. It employs the SBM to model intricate segments of these geometries and the MFS for the smooth ones. The proposed hybrid SBM-MFS method is studied in a 2D context in the framework of three benchmark examples involving acoustic radiation problems of circular-, square- and L-shaped objects in a full-space acoustic medium. In addition, the applicability of the proposed hybrid SBM-MFS methodology to predict the acoustic performance of a T-shaped thin barrier is also investigated. These examples are specifically designed to assess the feasibility, validity and accuracy of the hybrid SBM-MFS approach in comparison with the available analytical solutions and alternative numerical strategies such as the MFS, the SBM and the boundary element method (BEM). Numerical simulations demonstrate that the proposed method can match the level of accuracy of the MFS while keeps the robustness of the SBM when dealing with complex geometries, overcoming one the most important drawbacks of the traditional MFS. Moreover, the proposed hybrid SBM-MFS naturally avoids the non-uniqueness problem arising at the fictitious eigenfrequencies associated with the corresponding interior problems, a feature that neither the SBM nor the BEM inherently possesses., This research has been carried out with the financial support of the Acoustical and Mechanical Engineering Laboratory (LEAM) of the Universitat Politècnica de Catalunya (UPC) and the following research projects: • WIBWAY: Web-based computational tool for the assessment of vIBrations induced by railWAY traffic, with grant reference PDC2022-133093-I00, funded by MCIN/AEI/10.13039/501100011033 and by European Union “NextGenerationEU”/PRTR programme. Acronyms MCIN and AEI refer to Ministerio de Ciencia e Innovación and Agencia Estatal de Investigación, respectively. • AC-METATECH-EXP: Noise mitigation via acoustic meta-material technology: manufacturing and experimental validation, with grant reference TED2021-129413B-C22, funded by MCIN/AEI/10.13039/501100011033 and by European Union “NextGenerationEU”/PRTR programme. • IntRAIL, with reference PTDC/ECI-EGC/3352/2021, funded by FEDER funds through COMPETE2020 - Programa Operacional Competitividade e Internacionalização (POCI) and by national funds (PIDDAC) through FCT/MCTES. • VIBWAY: Fast computational tool for railway-induced vibrations and re-radiated noise assessment, with grant reference RTI2018-096819-B-I00, supported by the MCIN/AEI/10.13039/501100011033 and FEDER “Una manera de hacer Europa”. The first author would like to thank the financial support provided by the FPI-UPC 2017 grant (reference 07), funded by the Universitat Politècnica de Catalunya (UPC) and Banco Santander, Spain . Moreover, the fifth author would like to acknowledge the financial support of Fundação para a Ciência e a Tecnologia (FCT), I.P., by Base Funding (UIDB/04029/2020) and Programmatic Funding (UIDP/04029/2020) of the research unit “Institute for Sustainability and Innovation in Structural Engineering – ISISE”, and under the Associate Laboratory Advanced Production and Intelligent Systems ARISE under reference LA/P/0112/2020., Peer Reviewed, Postprint (published version)

This paper proposes a novel hybrid methodology that combines the singular boundary method (SBM) and the method of fundamental solutions (MFS) for the computational simulation of elastic wave propagation. Particularly, the methodology aims to address radiation or scattering problems of longitudinally invariant systems in the wavenumber–frequency domain involving boundaries with intricate geometries. The approach uses the SBM to deal with the complex parts of these geometries and the MFS for the smooth ones. The method is studied in the framework of three case studies involving longitudinally infinite cavities in a homogeneous full-space with circular, square-shaped and five-cusped hypocycloid cross-sections. These three examples are selected to assess the accuracy and robustness of the hybrid SBM-MFS approach in comparison with alternative modelling strategies. The comparisons show that the proposed method inherits the accuracy of the MFS while keeping the robustness of the SBM when dealing with complex geometries. The method is found to be computationally more efficient than the SBM or the boundary element method (BEM). Moreover, the hybrid approach naturally mitigates the effect of fictitious eigenfrequencies, a feature that neither conventional versions of the SBM nor the BEM have., This research has been carried out with the financial support of the Acoustical and Mechanical Engineering Laboratory (LEAM) of the Universitat Politècnica de Catalunya (UPC) and the following research projects: WIBWAY: Web-based computational tool for the assessment of vIBrations induced by railWAY traffic, with grant reference PDC2022-133093-I00, funded by MCIN/AEI/10.13039/501100011033 and by European Union “NextGenerationEU”/PRTR programme. Acronyms MCIN and AEI refer to Ministerio de Ciencia e Innovación and Agencia Estatal de Investigación, respectively. AC-METATECH-EXP: Noise mitigation via acoustic meta-material technology: manufacturing and experimental validation, with grant reference TED2021-129413B-C22, funded by MCIN/AEI/10.13039/501100011033 and by European Union “NextGenerationEU”/PRTR programme. IntRAIL, with reference PTDC/ECI-EGC/3352/2021, funded by FEDER funds through COMPETE2020 - Programa Operacional Competitividade e Internacionalização (POCI) and by national funds (PIDDAC) through FCT/MCTES. VIBWAY: Fast computational tool for railway-induced vibrations and re-radiated noise assessment, with grant reference RTI2018-096819-B-I00, supported by the MCIN/AEI/10.13039/501100011033 and FEDER “Una manera de hacer Europa”. The fifth author would like to acknowledge the financial support of Fundação para a Ciência e a Tecnologia (FCT), I.P. , by Base Funding (UIDB/04029/2020) and Programmatic Funding (UIDP/04029/2020) of the research unit “Institute for Sustainability and Innovation in Structural Engineering – ISISE”, and under the Associate Laboratory Advanced Production and Intelligent Systems ARISE under reference LA/P/0112/2020., Peer Reviewed, Postprint (published version)

An efficient three-dimensional approach for solving pile–soil interaction problems is proposed. In the approach, the soil is modelled as an elastic half-space, and its response in the presence of the pile’s corresponding cavity is computed by employing the singular boundary method. The pile is modelled analytically using the classic rod and Euler–Bernoulli beam theories. For the coupling with the soil, the pile is divided in a set of rigid segments that interact along their circumference with the soil. The methodology allows the rotational motions and reaction torques at these segments to be accounted for and their contribution in the accuracy of the scheme is assessed. A criterion to define the minimum number of collocation points that offers an acceptable trade-off between accuracy and numerical performance is also proposed. The method is validated against well-established methodologies and using the reciprocity principle that relates the wave radiation from the pile to the ground field with the incident wave problem due to a load on the ground surface. Results are shown for different soil stiffnesses and different pile length to diameter ratios. The employment of the singular boundary method is shown to provide strong computational advantages to detailed modelling approaches such as the three-dimensional finite element-boundary element method, as well as overcoming the fundamental limitations of plane-strain and axisymmetric methods., This research has been carried out with the financial support of three research projects: Project VIBWAY: Fast computational tool for railway-induced vibrations and re-radiated noise assessment, with reference RTI2018-096819-B-I00, supported by the MCIN/AEI/10.13039/501100011033 and FEDER “Una manera de hacer Europa”. Programmatic funding UIDP/04708/2020 of the CONSTRUCT (Instituto de I&D em Estruturas e Construções), funded by national funds through the FCT/MCTES (PIDDAC). Project PTDC/ECI-CON/29634/2017 (POCI-01-0145-FEDER-029634) and project PTDC/ECI-EGC/3352/2021, both funded by FEDER funds through COMPETE2020, Programa Operacional Competitividade e Internacionalização (POCI), and by national funds (PIDDAC) through FCT/MCTES. The first author would like to thank the ”Programa Nacional de Becas y Crédito Educativo” PRONABEC (www.pronabec.gob.pe) for the financial support given through the scholarship “Generación del Bicentenario de la República del Perú”., Peer Reviewed, Postprint (author's final draft)

In this work, an experimental validation of the hybrid methodology for the assessment of induced vibrations is presented. This methodology main advantage is the use of measurements as an input parameter, simplifying the usual numerical procedure, as it is no longer necessary to modulate the whole domain from the excitation source to the receiver, saving computational resources. It is determined a set of virtual forces, that when applied to the soil model induced the same displacement field on the location of the measurements. The application of these virtual forces to a soil-structure model will give the vibrations to which the structure will be subjected when will be constructed on that site. This methodology is validated experimentally on the Carregado experimental site, Postprint (published version)

The thesis focuses on studying train pantograph-catenary dynamic interaction, which is an essential aspect of railway engineering, as it can significantly impact the performance and safety of the railway system. The interaction between the pantograph and catenary lead to a vibrations in both the systems inducing a loss of contact between the pantograph and catenary, a highly undesirable problem for electrically powered transmission. In the dissertation, we will focus on a particular analytical method developed using a combination of Normal-mode Summation and Laplace Transformation, which was used to derive solutions for a variety of problems associated with a moving load on a catenary system. The first case tries to determine the efficacy of the mathematical method for this particular problem by considering the simplest case of a moving load on an elastic beam. The next chapter provides a more complicated and realistic model by the inclusion of damping for the continuous supports of the catenary. The solution developed for this case was validated using the analytical solution for an infinite beam. It was further used to verify the solutions developed on Ansys and Nastran. Finally, it was also used to verify a finite element model still under development. The analytical solution provides a robust solution to verify other numerical models being developed. Finally, the thesis also addresses the challenges and the limitations of each of these approaches and suggests ways they can be improved through future research., Incoming

This paper studies the problem of spurious eigensolutions in the context of the singular boundary method (SBM) formulated in the two-and-a-half-dimensional (2.5D) domain and proposes two numerical schemes to overcome this numerical difficulty. The SBM can be seen as a version of the method of fundamental solutions where the source points are located at the physical boundary. Similar to other boundary-type discretization schemes, the SBM also encounters the non-uniqueness problem at the vicinity of the eigensolutions of the corresponding interior problem. In the 2.5D domain framework, the so-called fictitious eigenfrequencies appearing in 3D problems arise in the form of spurious dispersion curves associated with propagation modes of the corresponding interior problem. The two enhanced 2.5D SBM approaches proposed in this work, based on the Burton–Miller method in one case and the dual surface method in the other, are designed to filter out the spurious eigenvalues from the simulation results and deliver accurate solutions along the wavenumber-frequency spectrum. Three benchmark examples including the radiation problems of an infinitely long cylinder under Dirichlet and Neumann boundary conditions and the radiation problem of a longitudinally infinite object with a constant star-like cross section subjected to a Dirichlet boundary condition are considered to study the proposed methods. The results demonstrate the capability of the proposed numerical schemes to successfully avoid the non-uniqueness problem when the 2.5D SBM is employed., Peer Reviewed, Postprint (published version)

More and more roller coaster manufacturing companies are interested in methods for predicting the vibration accelerations in a theoretical level. Nowadays, only the motion accelerations (G-forces) are computed theoretically by a specialised company during the design stage and this issue is also periodically assessed by the operators and certification companies, since there are regulations to comply in this matter. In contrast, vibration accelerations are not a legal factor to consider, until now. Furthermore, there is no wellestablished methodology to measure the vibration levels of a roller coaster. This thesis starts reviewing the current regulations and standards referred to the amusement industry, with special focus on vibration accelerations on roller coaster trains perceived by passengers. Later, this thesis exposes methods and techniques for predicting the vibration accelerations on a train of a steel roller coaster. Based on four selected research articles, a synthetization of the theoretical methods presented in the literature for predicting the vibration pattern of a roller coaster as a function of the vehicle and track parameters is presented. Emphasis on the kinematic constraint equations used for obliging a train to follow a particular trajectory is made. Moreover, this thesis studies the methodologies used in literature for measuring the vibration accelerations on a roller coaster train. Using similar techniques and equipment described on articles, an attempt of measuring roller coaster vibrations is done. The results obtained are analysed in the time domain with the graphs presented in the articles. Furthermore, the measures are transformed into the frequency domain for a better analysis of the recorded signals.

In this study, a novel 3D hybrid methodology for assessing re-radiated noise induced by railway traffic is presented. This method combines numerical modelling techniques with experimental measurements to provide a comprehensive evaluation. Instead of fully modelling the train-track-ground system, the proposed methodology offers an innovative approach to accurately quantify, in a first step, the elastodynamic response of the building in the form of vibrations. Then, the structural velocities are used as input for a model based on the Method of Fundamental Solutions (MFS), enabling the assessment of the acoustic response inside the building’s compartments. The ground-breaking aspect of the presented methodology lies in its ability to compute the dynamic response of the system without requiring any detailed information regarding the geometric or material properties of the track, rolling stock, and ground condition across the propagation path. The validation of this approach is achieved through a rigorous comparison between the results obtained using the hybrid method and those from a reference fully theoretical model of the system. The proposed hybrid methodology overcomes some of the limitations of traditional empirical models and offers a higher level of accuracy and flexibility in predicting railway-induced ground-borne noise, This work was financially supported by: • Base Funding - UIDB/04708/2020 and Programmatic Funding - UIDP/04708/2020 of the CONSTRUCT Instituto de I&D em Estruturas e Construçõoes – funded by national funds through the FCT/MCTES (PIDDAC); • Project PTDC/ECI-EGC/3352/2021, funded by national funds through FCT/ MCTES; • European Union’s Horizon 2020 Programme Research and Innovation action under Grant Agreement No 101012456 – In2Track3; • Individual Grant no. SFRH/BD/148276/2019, provided by FCT; • Individual Grant no. 2022.00898. CEECIND (Scientific Employment Stimulus - 5th Edition) provided by FCT; • Project WIBWAY: Web-based computational tool for the assessment of VIBrations induced by railWAY traffic, with grant reference PDC2022-133093-I00, funded by Agencia Estatal de Investigacíon (Spain) - Proyectos de Prueba de Concepto 2022, Postprint (published version)

In this article, a hybrid experimental/numerical methodology for the assessment of ground-borne noise and vibration in buildings to be constructed close to ground vibration sources is studied in a three-dimensional context. This methodology is based on three steps: First, the free field response due to the incident wave field induced by a particular ground vibration source is measured at the collocation points. Second, a set of virtual forces that equivalently represent the free field response induced by that incident wave field is then calculated. Finally, this set of virtual sources is applied to a structure-soil model to determine the response of the structure. In this paper, synthetic measurements are used to study different aspects related to the discretization strategies to be adopted to ensure accurate performance of the method. Specifically, two schemes for the distribution of virtual sources along the auxiliary surface are studied. Also, an exploration regarding the minimum number of collocation points that allows for a proper characterization of incident wave fields in the presence of shallow foundations is also presented. Of special relevance is the included discussion about sensor setup requirements for in situ experimental campaigns, Postprint (published version)

In this paper, a new meshless methodology to predict underground railway-induced vibrations is presented. In contrast to previous approaches, the proposed method uses meshless methods to model both the railway tunnel structure and the wave propagation in the surrounding soil. The method has been evaluated in the framework of an example of railway-induced vibrations using a shell with a square cross-section, embedded in a homogeneous full-space. The method is verified against an analytical solution considering different types of boundary conditions and compared with the 2.5D FEM-SBM and the 2.5D FEM-BEM approaches in terms of accuracy and computational efficiency. The presented comparisons illustrate that the proposed approach is a suitable strategy for predicting underground railway-induced vibrations, both in terms of accuracy and computational efficiency. Moreover, the use of meshless approaches for modelling both tunnel and soil not only simplifies the implementation of the approach but also makes it easier to use. Consequently, the proposed approach is found to be a suitable alternative tool for the prediction of railway-induced vibrations., Peer Reviewed, Postprint (published version)

Els recol·lectors electromagnètics d’energia de vibracions converteixen energia mecànica, en forma de vibracions, a electricitat. Són per tant, dispositius amb un gran potencial però també amb grans desavantatges pel que fa a adaptabilitat, eficiència i cost. El seu comportament és complex de caracteritzar, especialment quan hi ha una interacció magnètica significativa entre el propi dispositiu i components magnètics o electromagnètics externs, fet que podria derivar en un comportament no-lineal i afectar considerablement al seu rendiment. L’objectiu principal d’aquest projecte és el d’entendre millor la influencia d’aquestes forces magnètiques al rendiment mecànic d’aquest tipus de dispositius desenvolupant una eina de simulació que permeti predir el comportament d’un recol·lector sota diferents escenaris d’interès. El model que es proposa és el d’un sistema massa-esmorteïdor-molla d’un grau de llibertat amb forces magnètiques aplicades. La resposta del sistema és calculada per a una excitació d’entrada sinusoidal i a través de dos mètodes diferents. El primer és un mètode d’integració temporal mentre que el segon, conegut com a harmonic balance method, es calcula en l’espai freqüencial. Per unir la part magnètica amb la mecànica s’empra un acoblament dèbil; calculant en primer lloc les forces magnètiques que rep el dispositiu per posteriorment introduir-les en l’equació de moviment del sistema. Diferents tests experimentals representatius dels diversos escenaris a estudiar es duen a terme per tal de validar l’eina de simulació. Tant experimentalment com numèricament, en aquells casos en que hi ha forces magnètiques aplicades, s’observa un canvi substancial en la freqüència de ressonància del sistema, és a dir, un canvi en la seva rigidesa. Aquest canvi implica una reducció en la rigidesa del sistema quan l’imant del recol·lector està subjecte a forces d’atracció i un augment quan les forces són de repulsió., Electromagnetic vibration energy harvesters convert mechanical energy, in the form of vibrations, into electricity. They are, therefore, devices with huge potential but also with major drawbacks regarding adaptability, efficiency and return of investment. Their behaviour is complex to characterize, especially when there is a significant magnetic interaction between the device and external ferromagnetic or magnetic components, which could result in strong non-linear behaviours that might affect the performance of the device. The aim of this project is to understand better the influence of these magnetic forces on the mechanical system response by developing a simulation tool which can predict the behaviour of a harvester under different scenarios of interest. The proposed model is a one-degree-of-freedom spring-damper-mass system with applied magnetic forces. Its system response is computed for a sinusoidal excitation input and through two different methods. The former being a time domain integration method and the latter known as harmonic balance method, which is performed in the frequency domain. A weak coupling between magnetic and mechanical phenomena is assumed by performing the electromagnetic simulation independently and later inputting the results in the equation of motion of the system. Several experimental tests representing the different case scenarios are carried out in order to validate the simulation tool. Both experimentally and numerically, when magnetic forces are being applied, the harvester is seen to experience a significant shift in its resonant frequency, i.e., a change in its stiffness. This shift results in a softening effect if the oscillation magnet is subjected to attraction forces and in a hardening effect if, on the contrary, it is subjected to repulsion forces.

The power supply of electronic equipments is one of the major problems, during the construction of new structures. To provide this power supply, the main answer today is by building an electric network. However, this will increase the construction cost, and the technical maintenance, not to mention the cases where these networks will be impossible to setup. In response to these difficulties, autonomous power supplies like the electromagnetic vibration energy harvester started to be created. The electromagnetic vibration energy harvester is a set of three magnets, with the aim of obtaining an Halbach configuration, placed around a coil. The magnets will move when receiving vibration. Using this deplacement, the coil generates an electric current. The set of three magnets seems to be the most efficient system, but others parameters have to be taken into account, and research of other models keep on going. That’s why numerical modeling is used. This method allows us to observe different models, with the use of other parameters, to improve efficiency or study specific cases. The numerical modeling is based on two software : FEMM and EMS. The First, FEMM, creates 2D models, easy to handle, and can be driven by MatLab. The second, EMS, is an extension of SolidWorks or, in our case, Autodesk Inventor, that allows us to apply electromagnetic study to the 3D model of these softwares. At the start of this project, FEMM was already used to compare different models. But, the software allows only 2D and static studies. A change to EMS would allow 3D and dynamic models. That is why, the main goal of this project is learning how EMS works, the differences between the two software, and if an observation made on a software can be admitted on the other software. In a first time, a simple model, with only one magnet that replaced three other magnets with the same magnetic flux, was studied. The use of FEMM allowed to show different stages of this model, according to the distance betwe, Incoming

This thesis studies the vibration pattern synthesis in structures using the Dynamic Mode Decomposition (DMD) method. This numerical model is used for one degree of freedom, to know the axial response, according to x. Firstly the effectiveness of the DMD method is evaluated and give good results to reconstruct the signal, applying to initial conditions of the structure's vibration to extract the shape and temporal characteristics of the DMD modes, which were then used to synthesize the desired vibration pattern in the structure. Next, QR factorization is used in order to find sensor placement. Results showed that the DMD method, combined with QR factorization, can effectively synthesize the desired vibration pattern in structures. However, conditions about spacing of the sensors is necessary to optimize the interpolation. Regarding further research, it’s needed to study the method's limitations and potential application in more complex systems or when dealing with high-frequency data., Incoming

En aquest treball es presenta una proposta d’implementació del manteniment preventiu. Aquest es basa en anàlisi de vibracions a les màquines més importants del procés productiu de la fàbrica Knauf de Guixers (Solsonès). Es defineixen les diferents eines que es disposa per tal de fer els anàlisis i la metodologia seguida per a un diagnòstic exitós. També es veuran les mesures preses més rellevants amb els seus diagnòstics i resultats reals que s’han anat obtenint. I finalment, es mostrarà la metodologia seguida per implementar l’anàlisi de vibracions i es detalla un pla de formació a un mecànic a càrrec de l’empresa., En este trabajo se presenta una propuesta de implementación del mantenimiento preventivo. Éste se basa en análisis de vibraciones en las máquinas más importantes del proceso productivo de la fábrica Knauf de Guixers (Solsonès). Se definen las diferentes herramientas que se dispone para realizar los análisis y la metodología seguida para un diagnóstico exitoso. También se verán las medidas tomadas más relevantes con sus diagnósticos y resultados reales que se han obtenido. Y, finalmente, se mostrará la metodología seguida para implementar el análisis de vibraciones y se detalla un plan de formación a un mecánico a cargo de la empresa., This work will see the implementation of preventive maintenance based on vibration analysis on the most important machines in the production process of the Knauf factory in Guixers (Solsonès). It defines the different tools available to perform the analysis and the methodology followed for a successful diagnosis. It could be seen the most relevant steps taken with your diagnoses and the actual results that have been obtained. And finally, it will show how to implement vibration analysis with training for a mechanic in charge of the company.

Prediction of vibrations in buildings due to railway traffic is challenging due to several aspects, namely the huge dimensions of the domain, the interaction between different systems, and the uncertainties inherent to the complexity of the system. Therefore, experimental/numerical hybrid prediction techniques are of great interest since they take advantage of the combination between experimental data and numerical resources. In this context, the type of foundations of a building are preponderant in the dynamic soil-structure interaction effect and may have an influence on the accuracy of the hybrid prediction. The presence of the building foundations could significantly modify the response of the local sub-soil of the building. This fact makes that the prediction of vibrations in buildings becomes a complex wave propagation problem. As different types of foundations behave differently, they lead to different dynamic responses in the structure for a prescribed incident wave field. Therefore, dynamic soil-structure interaction coupling is also affected by the building’s foundation type. In order to investigate this phenomenon, this paper studies the influence that the consideration of three different foundation typologies, shallow, slab and deep foundations, have on the prediction of railway-induced vibrations on a building using an experimental/numerical hybrid methodology. A comparison is made between the results obtained through the hybrid method and the numerical results obtained through a numerical model based on the full system, Postprint (author's final draft)

Nowadays the industry spends massive amounts of money on the supervision and replacement of rail fasteners. This happens due to the fact that damaged fasteners generate vibrations and noise, which is uncomfortable and disturbing to the inhabitants of the area, in addition to the safety risks that can be associated with it. These costs could be reduced by incorporating the in-situ characterization method. This method is based on the excitation and obtention of measurements at specific locations on the track to be able to recover the stiffness of each of the fasteners. The objective of this thesis is to verify the experimental feasibility of the in-situ characterization method for obtaining the fasteners' stiffness in railway tracks using numerical models. For this purpose, some of the measurements provided by the simulation will be discarded (thus emulating the lack of sensors, since theoretically there should be as many as the number of fasteners on the track) and it will be attempted to obtain the stiffness of the fasteners. The thesis will consider two simulations: a simplified model, including 1D elements, and a more realistic model, including 3D solids. Afterwards, a MATLAB code will process the results and show the stiffnesses obtained for each fastener. The results indicate that for both the simplified model and the 3D model, the in-situ method can recover each stiffness when using all the measurements. For both cases, they also show that the closest fasteners to the one that has been discarded obtain a less accurate stiffness, while the more fasteners are between the studied and discarded fastener, the more accurate the stiffness is. In addition, the closest fasteners to the discarded one obtain a higher stiffness at low frequencies, considering the loss of stiffness. Another important fact is that the retrieved fasteners’ stiffness at high frequencies usually tends to the right value. Finally, when disregarding measurements, the stiffness values for the 3D m

This paper proposes and studies a ring-shaped architecture with Halbach configuration for electromagnetic vibration energy harvesters. The proposed transducer consists of three ring magnets with a linear Halbach array that concentrates its magnetic field in the inner space of the mechanism where a single vertically-centered concentric coil has been located. This particular structure allows to increase the resonant mass within a fixed dimensions of the transducer and reduces the coil resistance for the same number of turns, enhancing its power generation capabilities. The ring-shaped architecture has been compared with several ring magnet arrangements, including single magnets, double-magnet arrays, and an alternative linear Halbach array, using numerical simulations to determine their influence on its performance. Consequently, this work is the first contribution to the applicability of Halbach configurations for electromagnetic vibration energy harvesters within ring-shaped architectures. Also, a geometrical optimization of the proposed transducer has been conducted, mainly as a function of the inner radius, the height, and the wire diameter of the coil, to increase its power generation. The maximum simulated output power for the optimized generator reaches 3.61 mW for an input harmonic vibration of 0.03 g at a frequency of 61.7 Hz, corresponding to a 29.08 mW/cm 3 g 2 normalized power density performance, significantly higher than devices described in the literature for similar applications. Besides, a harvester prototype based on the proposed configuration has been fabricated to validate the modeling strategy used and to certify the reliability of the proposed design regarding power generation capabilities. Several experimental tests have been conducted under harmonic excitation with frequencies ranging between 10 Hz and 100 Hz and a vibration amplitude of 0.03 g. The experimentally measured induced voltage and electrical output power have been found in good agre, Postprint (published version)

In this paper, a numerical methodology based on a two-and-a-half-dimensional (2.5D) singular boundary method (SBM) to deal with acoustic radiation and scattering problems in the context of longitudinally invariant structures is proposed and studied. In the proposed 2.5D SBM, the desingularisation provided by the subtracting and adding-back technique is used to determine the origin intensity factors (OIFs). These OIFs are derived by means of the OIFs of the Laplace equation. The feasibility, validity and accuracy of the proposed method are demonstrated for three acoustic benchmark problems, in which detailed comparisons with analytical solutions, the 2.5D boundary element method (BEM) and the 2.5D method of fundamental solutions (MFS) are performed. As a novelty of the present study, it is found that the 2.5D SBM provides a higher numerical accuracy than the 2.5D linear-element BEM and lower than the 2.5D quadratic-element BEM. Although the results obtained depict that a nodal approximation of the boundary geometry leads to a significant reduction in the accuracy of the 2.5D SBM, the delivered errors are still acceptable. For complex geometries, the 2.5D SBM is found to be simpler and more robust than the 2.5D MFS, since no optimization procedure is required., Peer Reviewed, Postprint (published version)

This thesis is concerned with the development of efficient and practical numerical methodologies to deal with longitudinally invariant soil-structure interaction problems in elastodynamics. All the approaches appearing in this thesis are formulated in the frequency-wavenumber domain. Moreover, the formulations can deal with full-space and half-space models of the soil. The novel proposed methods are mainly based on meshless approaches, which provide three main benefits: simplicity on the formulation and implementation, to avoid meshing requirements and to increase the computational efficiency of the evaluation of the soil-structure system response. Generally, these approaches are employed to model the wave propagation in unbounded mediums. Thus, in this thesis, meshless methods are used to model the soil, while the finite element method is mainly used to deal with the structure modelling. However, this thesis also demonstrates that meshless methods can also be used to model homogeneous structures. The performances of the novel approaches presented have been assessed in the context of railway tunnels embedded in the soil, especially for the case studies of circular and cut-and-cover tunnels. The studies are carried out for different elastodynamic models of the soil, including homogeneous full-space, homogeneous half-space and horizontally layered half-space. Four new methodologies are presented in this thesis. Firstly, a two-and-a-half-dimensional finite element-boundary element methodology coupled with the method of fundamental solutions is developed. This approach uses the method of fundamental solutions to model the wave propagation in the soil once the soil-tunnel interaction has been determined, reducing the computational needs of computing the soil response. Afterwards, the second methodology further enhances the computational efficiency, the robustness and the simplicity of the approach, by modelling the soil response using the singular boundary method. To rea, Esta tesis se centra en el desarrollo de metodologías numéricas prácticas y eficientes para tratar con problemas de interacción sólido-estructura longitudinalmente invariantes en elastodinámica. El conjunto de enfoques que aparecen en esta tesis está formulado en el dominio de la frecuencia y del número de onda. Además, las formulaciones pueden tratar el terreno con modelos de espacio completo y con modelos de semiespacio. Los nuevos métodos propuestos están principalmente basados en enfoques sin malla, los cuales aportan tres beneficios principales: simplicidad en la formulación e implementación, evitar los requisitos del mallado y un incremento de la eficiencia computacional requerida por la evaluación de la respuesta del sistema terreno-estructura. Generalmente, estos enfoques se emplean para modelizar la propagación de ondas en medios infinitos. Debido a esto, en esta tesis, los métodos sin malla se usan para modelizar el terreno, mientras que el método de los elementos finitos se usa principalmente para tratar con la modelización de la estructura. Sin embargo, esta tesis también demuestra que los métodos sin malla también se pueden usar para modelizar estructuras homogéneas. El desempeño de los nuevos enfoques presentados ha sido evaluado en el contexto de túneles ferroviarios en el terreno, en especial para los casos de túneles circulares y túneles cut-and-cover. Los estudios han sido realizados para distintos tipos de modelos elastodinámicos del terreno, incluyendo espacios completos, semiespacios homogéneos y semiespacios con estratificación horizontal. En esta tesis se presentan cuatro metodologías nuevas. Inicialmente, se desarrolla una metodología dos-y-medio-dimensional de elementos finitos con elementos de contorno acoplada con el método de las soluciones fundamentales. Este enfoque usa el método de las soluciones fundamentales para representar la propagación de ondas en el terreno una vez la interacción terreno-estructura ha sido determinada, reduciend, Postprint (published version)

In this paper, a novel numerical methodology to deal with longitudinally invariant soil–structure interaction problems is proposed. The methodology uses the finite element method to model the structure and the singular boundary method to model the wave propagation in the soil, both formulated in the wavenumber–frequency domain. The versatility presented by the finite element method combined with the simplicity and computational efficiency of the singular boundary method results in a friendly, robust and accurate novel methodology to address the soil–structure interaction problems. The accuracy of the proposed method is assessed by comparing it against 2.5D FEM–MFS and 2.5D FEM–BEM approaches for two cases: a thin cylindrical shell and a star-like beam structure, both embedded in a full-space medium. Moreover, the computational efficiency of the proposed method is evaluated against 2.5D FEM–MFS and 2.5D FEM–BEM methods. In the final step, the applicability of the proposed method is studied through an example of a railway tunnel embedded in a layered half-space. The results presented in this work exhibit the advantages of the novel approach in modelling simplicity, numerical efficiency and robustness with respect to previous methodologies., Peer Reviewed, Postprint (published version)

This paper presents an efficient method to predict underground railway-induced vibrations. The method uses the finite element method (FEM) to model the railway tunnel structure and the singular boundary method (SBM) to model the wave propagation in the surrounding soil. The FEM mesh and the distribution of SBM collocation points at the tunnel/soil interface are generated using an automatic meshing strategy. The presented method is one of the main components of VIBWAY, a user-friendly prediction tool to address railway-induced vibration problems. This paper presents three calculation examples in which the soil response due to forces applied on the tunnel structure are computed in terms of transfer functions. The results obtained for each one of the calculation examples are compared with those computed using a model based on a 2.5D FEM-BEM approach. The presented comparisons show that the proposed approach is a suitable strategy for predicting underground railway-induced vibrations, both in terms of accuracy and computational efficiency. Moreover, the use of an automatic meshing strategy and the SBM formulation not only eases the implementation of the approach but it also makes it easier to use, which is one of the key features of the VIBWAY tool., Peer Reviewed, Postprint (published version)

In this paper, a novel hybrid 2.5D SBM-MFS approach is formulated and developed in the frequency domain. This approach inherits the accuracy of MFS while keeping the robustness presented by the SBM. The MFS is employed to study the smooth portion of the boundary, while the complex segments are analysed through the SBM. For the sake of presenting the potential of the proposed hybrid approach, a square-shaped boundary excited by a unit point load is considered. The performance of the hybrid method is thoroughly assessed against 2.5D BEM, MFS, and SBM methods, in terms of convergence error analysis. Since the considered problem does not have a known analytical solution, the 2.5D FEM-BEM approach with a highly refined mesh is taken as the reference in the error analysis. The convergence error is calculated in terms of receptances at two circular distributions of evaluation points. In the hybrid method, 70 percent of the virtual sources are allocated on an auxiliary virtual boundary (MFS sources) while the remaining 30 percent are allocated on the physical boundary (SBM sources). The convergence plots obtained by four methods show that the accuracy of the hybrid method is significantly higher than the one of MFS and, in some cases, even higher than the one of BEM. While MFS requires a large number of nodes per wavelength to achieve acceptable results, the 2.5D SBM-MFS presents a high convergence rate, even for a small number of nodes per wavelength. The main benefit of the hybrid method is not solely its accuracy, compared with the BEM and SBM methods, but also its computational efficiency is another achievement. Moreover, in contrast to integration-based methods, such as BEM, the implementation of the new procedure is quite simple. It can be concluded that the hybrid 2.5D SBM–MFS is an adequate alternative prediction tool for elastodynamic problems., Peer Reviewed, Postprint (published version)

This research is concerned with the impact of onboard passengers’ seating arrangement on the carbody flexural vibrations of a high-speed railway vehicle. In this regard, the previously developed passenger body-seat models are used to consider the dynamic influence of the passengers. The carbody is modeled using the Euler–Bernoulli beam model to evaluate its flexural deformation. The frequency-domain analysis demonstrates that the carbody behaves almost like a rigid body when the vehicle is full of passengers. It is established that the passengers' presence causes a 31% enhancement of the ride quality determined based on EN 12299 standard for a fully occupied vehicle compared with an empty car. A scaled model of a ratio of 1:24.5 of the Shinkansen vehicle is constructed for validation purposes. The experimental results exhibit a similar trend as found by the simulations in terms of the impact of the passengers’ distribution on the carbody flexural vibrations, Postprint (author's final draft)

Electromagnetic vibration energy harvesting is a relatively modern technology that has received relevant attention in the last decade from the research community and industry as a potential complement or alternative to the inconvenient employment of batteries for powering ultra-low-power devices, microelectromechanical systems, and wireless sensor networks. However, there are still many flaws in this technology that require to be addressed to develop truly practical, reliable, and cost-effective electromagnetic generators, without which industries can still not avoid relying primarily on batteries for powering wireless devices. This dissertation is mainly concerned with developing a high-power, compact, and yet simplified electromagnetic vibration energy harvester capable of reaching high power density levels without the necessity of a complex design, which is generally accompanied by an increment in fabrication costs. For this purpose, a ring-shaped magnet structure consisting of three ring magnets in a linear Halbach configuration is proposed in the present thesis. This particular structure is also compared, in terms of their output performance, with several ring magnet arrangements that include single magnets, double magnet arrays, and an alternative Halbach configuration to determine the actual benefits of the employed Halbach array within the proposed architecture. Also, the coil-magnet parameters of the selected transducer have been further optimized, mainly as a function of the inner radius, the height, and the wire diameter of the coil, to maximize its power generation. Besides, a harvester prototype based on the proposed configuration has been fabricated to validate the modeling strategy used and to certify the reliability of the proposed design regarding its power generation capabilities. The results of the power density normalized to the square of the excitation amplitude obtained for the optimized device and the fabricated prototype are found to be signi, La recolección de energía de vibración mediante transductores electromagnéticos es una tecnología relativamente moderna que ha recibido especial atención en la última década por parte de la comunidad científica e industrial como una potencial alternativa al uso de baterías para alimentar dispositivos de ultra baja potencia, sistemas microelectromecánicos y redes de sensores inalámbricos. Sin embargo, existen aún muchas problemáticas en esta tecnología que requieren ser atendidas para poder desarrollar generadores electromagnéticos realmente prácticos, confiables y económicos, necesarios para proveer a la industria de una solución confiable que permita no depender primordialmente de las baterías para alimentar dispositivos inalámbricos. Esta tesis doctoral se enfoca fundamentalmente en el desarrollo de un recolector de energía de vibración mediante transducción electromagnética, de alta potencia, compacto y simplificado, capaz de alcanzar altos niveles de densidad de potencia generada sin la necesidad de un diseño complejo, el cual, generalmente, viene acompañado de un incremento de los costes de fabricación. Para este propósito, esta tesis propone una estructura magnética formada por tres imanes anulares en configuración Halbach lineal. Para determinar los beneficios reales de la configuración Halbach empleada dentro de la arquitectura propuesta, esta estructura en particular se compara, en términos de rendimiento de salida, con varias configuraciones de imanes anulares: un único imán, dos imanes y una configuración Halbach alternativa. Además, los parámetros del sistema bobina-imán del transductor seleccionado han sido optimizados, principalmente en función del radio interno, la altura y el diámetro del cable de la bobina, para maximizar su generación de potencia. Adicionalmente, se ha fabricado un prototipo de recolector de energía basado en la configuración propuesta para validar la estrategia de modelado utilizada y certificar la fiabilidad del diseño propuesto, Postprint (published version)

This paper aims to introduce preliminary statement of methods of a computationally efficient and user-friendly toolbox, called VIBWAY, able to predict vibration and re-radiated noise levels in two situations. On the one hand, it can predict levels in existing buildings due to new lines or after the application of mitigation measures in existing operational railway infrastructures. Thus, it can be used to assess the performance of vibration countermeasures applied at the track, at the soil and/or at the building. On the other hand, it allows for the prediction of the response of new buildings to be constructed close to an existing railway line from vibration measurements in the surface of the ground where the building will be constructed. The VIBWAY toolbox is based on a non-interface 2.5D FEM-SBM approach for the wave propagation on the soil, on semi-analytical approaches for the track and the building and on rigid multibody dynamics modelling of the train vehicle, Postprint (published version)

In this work, an experimental/numeric hybrid methodology for the assessment of building induced vibrations due to railway traffic is presented. This method has as main advantage the use of measurements of the actual vibration field to the terrain surface as an input parameter. The main application for this method is the study of the vibrations that a given building will be subjected to when built close to a railway line. A set of virtual forces is applied to a sub-model of the ground alone, making this displacement field equal to the one that is measured experimentally, allows obtaining the virtual forces to be applied to the soil-building model and which will give the vibrations to which the same building is subjected. In the present work, this methodology is presented and validated numerically by 2.5D for a case of homogeneous and stratified soil. The proposed hybrid model simplifies the usual numerical procedure as it is no longer necessary to modulate the railway infrastructure and reduces the uncertainty of the prediction due to the use of experimental site measurements, This work was financially supported by: Programmatic funding - UIDP/04708/2020 of the CONSTRUCT - Instituto de I&D em Estruturas e Construções - funded by national funds through the FCT/MCTES (PIDDAC); Project PTDC/ECM-COM/1364/2014 – POCI-01-0145-FEDER-016783 – 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, I.P; Project POCI-01-0145-FEDER-029557 – funded by FEDER funds through COMPETE2020 – Programa Operacional Competitividade e Internacionalização (POCI) and by national funds (PIDDAC) through FCT/MCTES; Individual Grant SFRH/BD/148276/2019; Project VIBWAY: Fast computational tool for railway-induced vibrations and re-radiated noise assessment, with reference RTI2018-096819-B-I00, supported by the Ministerio de Ciencia e Innovación, Retos de Investigación 2018, Postprint (published version)

L’objectiu d’aquest treball de fi de grau ha estat estudiar solucions per mitigar l’impacte de les vibracions generades pels rotors verticals en un prototip de drone VTOL encara en fase de disseny. Aquest model pertany a l’empresa catalana Catuav, amb la que s’ha acordat com s’abordava el disseny de les solucions. D’aquesta manera, en aquest memòria es recullen cronològicament explicats les diferents fases del projecte. En primer lloc, s’ha dut a terme una caracterització del comportament dinàmic de l’estructura afectada. Amb aquest objectiu, s’ha realitzat un estudi de les dades de la IMU de vols previs, un anàlisi modal experimental i un anàlisi modal operacional. És important remarcar que aquesta fase no ha estat fixe. S'ha allargat i modificat acord amb la informació que s'anava obtenint per tal de poder obtenir la informació necessària per poder dissenyar les solucions. A partir d’aquí, s’ha construït un model d’elements finits amb el mateix comportament dinàmic. L’objectiu d’aquest ha estat poder avaluar l’eficàcia de les solucions dissenyades sense necessitat d’implementar-les a l’estructura real. Seguint les pautes marcades per Catuav, el següent pas ha consistit en analitzar quina afectació al comportament dinàmic tenien diferents possibles modificacions estructurals. Per últim, s’ha estudiat els resultats obtinguts per tal de proposar diferents línies d’actuació per a mitigar l'efecte de les vibracions., The aim of this final degree project has been to study solutions to mitigate the impact of the vibrations generated by the vertical rotors on a prototype VTOL drone still in the design stage. This model belongs to the Catalan company Catuav, with which it has been agreed how the design of the solutions was approached. In this way, this report explains chronologically the different phases of the project. In first place, a characterization of the dynamic behavior of the affected structure has been carried out. To this end, an analysis of the IMU data from previous flights, an experimental modal analysis and an operational modal analysis have been performed. It is important to note that this phase of the project has not been fixed at any moment. It has been extended and modified according to the information that was being obtained in order to be able to get the necessary information to develop the possible solutions. From this, a finite element model with the same dynamic behavior has been built. The aim of this has been to be able to evaluate the effectiveness of the designed solutions without having to implement them in the real structure. Following the guidelines set by Catuav, the next step has been to analyze what impact on dynamic behavior had different possible structural modifications. Finally, the results obtained have been studied in order to propose different lines of action to mitigate the effect of vibrations.

In this project the validity of an in-situ method to evaluate resilient elements is verified for systems with more than one connection. Potential advantages of this method would be testing elements under more realistic and representing conditions, as well as greater flexibility of the systems that can be evaluated. An introduction to the necessary theoretical formulation is given as well as an evaluation of the current state of the art. The theoretical formulation also includes a theoretical demonstration of the method for multiple connections. The method is validated using a combination of numerical models based on the Finite Element Method as well as different experiments conducted in a laboratory. The numerical models not only validate the hypothesis that the method can be applied to systems with multiple connections, but they are also used to study the effect of neglecting some of the degrees of freedom that describe these connections. The experimental case studies were divided in two parts, one with a single isolator to validate the laboratory setting used and a second one where multiple connections were considered. The results obtained for this second case were compared with those from the theoretical basis and the numerical models and this showed that they were erroneous. The comparison highlighted that these discrepancies can be attributed to the fact that some degrees of freedom of the system that were not initially measured may play an unexpectedly important role in this case study, and this led to the accumulation of error. The results show that this method is valid but it may be mainly applicable to cases where all the degrees of freedom of the system are known and can be measured. Future possible lines of research are included on the project and expand on the possibilities of both the numerical and the experimental methods to view how modifications to the system affect the results., En este proyecto la validez de un método in-situ para evaluar elementos aisladores es verificada para sistemas con más de una conexión. Las ventajas potenciales de este método serían poder evaluar elementos bajo condiciones más realistas y representativas, así como mayor flexibilidad en los tipos de sistema que pueden ser evaluados. Está incluida en el trabajo una introducción al marco teórico necesario, así como una evaluación del estado del arte actual. El marco teórico también incluye una demostración teórica del método para múltiples conexiones. El método ha sido validado usando una combinación de modelos numéricos basados en el método de elementos finitos y experimentos realizados en un laboratorio. Los modelos numéricos no solo validan la hipótesis de que el método se puede aplicar a sistemas con múltiples conexiones, sino que también se usan para estudiar el efecto de ignorar algunos de los grados de libertad que describen las conexiones. Los casos de estudio experimentales fueron separados en dos partes, la primera con un elemento aislante para evaluar la configuración del laboratorio y una segunda parte donde se utilizaron múltiples conexiones. Los resultados conseguidos en ese segundo caso fueron comparados con aquellos de la base teórica y los modelos numéricos y se observó que eran erróneos. La comparación resaltó que esas discrepancias podían ser atribuidas al hecho de que algunos grados de libertad dedl sistema que no habían sido medidos en un principio podían tener un rol más importante de lo esperado en este caso de estudio y eso llevó a una acumulación del error. Los resultados generales muestran que el método es válido pero podría ser solo aplicable a casos en los cuales todos los grados de libertad del sistema son conocidos y pueden ser medidos. The results show that this method is valid but it may be mainly applicable to cases where all the degrees of freedom of the system are known and can be measured. Algunas posibles líneas de investigación fu

This thesis is focused on the enhancement and development of advanced methodologies for the dynamic characterisation of resilient elements used in railway applications. On the one hand, this thesis proposes several improvements to the application of the indirect method described in ISO 10846 standard for determining the dynamic stiffness of resilient elements using a swept-sine excitation. Within this framework, this work proposes a method that allows to design the swept-sine excitation parameters in order to ensure a predefined maximum error of those estimated frequency response functions that are needed to determine the dynamic stiffness. This method is based on a procedure that uses a numerical simulation of the test-rig and the resilient element of study which allows to predict the error made as a function of the excitation parameters and of the existing background noise, allowing to optimise the test in terms of required time and results quality. The method is then validated experimentally for two case studies: a sample of an elastomeric material and a coil spring. This work has also studied the influence that the experimental setup, the static preload and the dynamic loading have on the estimation of the frequency response functions. On the other hand, this thesis considers the adaptation of an existing in situ methodology to laboratory testing. The methodology allows to determine the dynamic stiffness of an elastic element in a broad frequency range with a single test. This alternative methodology has been validated using the two case studies previously mentioned. By including the improvements made to the indirect method to this methodology, it is possible to obtain a simple and robust method that can take into account the uncertainty related to several effects such as the excitation, the background noise and the experimental setup. Finally, the dynamic stiffness results obtained for both case studies have been compared to the results obtained using standardi, La presente tesis se enfoca en la mejora y desarrollo de metodologías avanzadas para la caracterización dinámica en laboratorio de materiales resilientes para aplicaciones ferroviarias. Por un lado, la tesis propone una serie de mejoras para la aplicación del método indirecto descrito en la norma ISO 10846 para la determinación de la rigidez dinámica de elementos elásticos en el caso de excitación por barrido sinusoidal. En este marco, se propone un método que permite diseñar los parámetros de la excitación de barrido sinusoidal para asegurar un determinado error máximo en la estimación de las funciones de respuesta en frecuencia necesarias para la determinación de la rigidez dinámica. Este método se basa en un proceso de simulación numérica sobre el banco de ensayos de laboratorio y el elemento resiliente a estudiar el cual permite estimar el error que se cometerá en función de los parámetros de la excitación y el ruido de fondo existente, permitiendo la optimización del ensayo en tiempos y calidad. El método es posteriormente validado experimentalmente a partir de dos casos de estudio: un espécimen de material elastomérico y un resorte helicoidal. También se ha estudiado qué influencia tienen sobre la estimación de las funciones de respuesta en frecuencia el tipo de montaje, la precarga estática y la carga dinámica. Por otro lado, esta tesis presenta la adaptación de una metodología in situ ya existente para su aplicación a ensayos de laboratorio. Esta metodología permite determinar la rigidez dinámica de elementos elásticos en todo un rango frecuencial a partir de un único ensayo de laboratorio. Esta metodología alternativa se ha validado para los dos ejemplos experimentales antes mencionados. Aplicando las mejoras antes mencionadas para el método indirecto a esta metodología, se obtendría un método simple y robusto que tendría en cuenta la incertidumbre de medida asociada a varios efectos cómo la excitación, el ruido de fondo y el montaje. Finalmente, los result, Postprint (published version)

En aquest treball es desenvolupa un model FEM d’una via en placa ferroviària. Aquest model es desenvolupa en el marc d’un estudi de noves metodologies per a la determinació in situ de la rigidesa dinàmica de les fixacions de carril o altres elements elàstics d’una via ferroviària. El model FEM desenvolupat és tridimensional però s’ha desenvolupat amb elements finits de placa i biga per tal de simplificar-ne l’ús. El model considera un tram de via en placa amb un total de 5 lloses on els carrils es modelitzen com a bigues, les fixacions com a molles i les lloses com a plaques finites. L’estudi contempla també l’anàlisi dels modes propis del sistema per tal d’assegurar la qualitat del model desenvolupat. S’obtenen i s’analitzen les receptàncies associades als punts de contacte de les fixacions amb els carrils i la llosa per la llosa central. A partir de les anàlisis realitzades al model, es determina que el mateix és vàlid per a la realització d’estudis numèrics sobre metodologies per la determinació in situ les propietats dinàmiques de fixacions de carril., En este trabajo se desarrolla un modelo FEM de una vía en placa ferroviaria. Este modelo se desarrolla en el marco de un estudio de nuevas metodologías para la determinación in situ de la rigidez dinámica de las fijaciones de carril u otros elementos elásticos de una vía ferroviaria. El modelo FEM desarrollado es tridimensional pero se ha desarrollado con elementos finitos de placa y viga para simplificar su uso. El modelo considera un tramo de vía en placa con un total de 5 losas donde los carriles se modelizan como vigas, las fijaciones como muelles y las losas como placas finitas. El estudio contempla también el análisis de los modos propios del sistema para asegurar la calidad del modelo desarrollado. Se obtienen y analizan las receptancias asociadas a los puntos de contacto de las fijaciones con los carriles y la losa para la losa central. A partir de los análisis realizados en el modelo, se determina que el mismo es válido para la realización de estudios numéricos sobre metodologías para la determinación in situ las propiedades dinámicas de fijaciones de carril., In this project, a FEM model of a railway plate track is developed. This model is developed in the framework of a study of new methodologies for the in situ determination of the dynamic stiffness of rail fasteners or other elastic elements of a railway track. The FEM model developed is three-dimensional but it has been developed with finite plate and beam elements in order to simplify its use. The model considers a section of track in plate with a total of 5 slabs where the rails are modeled as beams, the fasteners as springs and the slabs as finite plates. The study also includes the analysis of the system's eigenmodes in order to ensure the quality of the model developed. The receptances associated with the points of contact of the fasteners with the rails and the slab are obtained and analyzed for the central slab. Based on the analysis performed on the model, it is determined that the model is valid for conducting numerical studies on methodologies for the in situ determination of the dynamic properties of fasteners.

In this research, the effect of rail vehicle carbody’s flexural modes on the ride comfort of an example high-speed railway vehicle is investigated. The vehicle is modeled as a rigid multi-body system, where the rigid body vertical, longitudinal, pitch, and roll degrees of freedom of the carbody and bogie frames and the rigid body vertical and roll degrees of freedom of the wheelsets are considered. An Euler–Bernoulli beam theory is used to account for the flexural motion of the carbody. The longitudinal interaction between carbody and bogie through the traction rod is modeled as a nonlinear spring element. The corresponding equations of motion of the system in the frequency domain are obtained by using the equivalent linearization method. The effect of the traction rod is explored by using this model. Also, the optimal stiffness of the traction rod element that minimizes the flexural vibrations of the carbody is obtained through a genetic algorithm. With the optimal stiffness for the traction rod, the ride quality index at the center of the carbody floor is improved by 41% at a speed of 300 km/h. For the validation of numerical results, a scaled model of the vehicle with a scale factor of 24.5 was constructed, and its associated results are presented. The model was excited by random input signals, which were generated based on the power spectral density of the track irregularity function. The agreement between the simulation results and the scaled experimental outcome when compared with the measured data from other sources is found to be satisfactory. In the framework of the physical scaled model, the filtering effect due to the vehicle bogie base is also examined, Postprint (author's final draft)

Electromagnetic vibration energy harvesting is a relatively new technology that transforms kinetic energy from mechanical vibrations into electrical energy, allowing the substitution of batteries or cables for powering ultra-low-power devices like wireless sensor networks for structural health monitoring. For this aim, different magnet and coil configurations have been proposed for the design of these harvesters by several researchers. In this paper, four cylindrical “Magnet in-line coil” configurations with back steel, which include a typical single-magnet, a double-magnet array, and two proposed cylindrical Halbach magnet arrays of three and five magnets, are analyzed using the finite element method and compared in terms of their magnetic flux linkage and transduction factor. The numerical simulations are conducted in all cases with the same materials properties, coil parameters, and geometrical boundaries, the latter consisting of the total cross-sectional area of the magnets and the coil, the air gaps, and the total volume of the transducer mechanism. Furthermore, the design that provides the best performance is analyzed with two different coil configurations. It is finally found that the proposed cylindrical Halbach magnet array with three magnets and one-center coil presents the best results, reaching an average transduction factor of 95.83 Vs/m and a normalized power density of 19.72 mW/cm3g2., Peer Reviewed, Postprint (published version)

A novel experimental/numerical hybrid methodology for the assessment of railway-induced ground-borne vibration in buildings based on experimental measurements in the soil surface is proposed in this paper. This methodology has been specifically designed for the prediction of railway-induced vibration in buildings to be constructed close to an operative railway infrastructure, although it can be applied for other types of vibration sources. The model of the incident wave field induced by the railway infrastructure consists of a set of virtual forces applied in the soil, which would be obtained from vibration experimental measurements in the surface of the ground where the building will be constructed. These virtual forces can be subsequently applied to a model of the building-soil system to obtain a prediction of the vibration levels that will be induced by the existing railway infrastructure to the studied building. In the present work, this methodology is theoretically defined and it is numerically validated for two-dimensional and two-and-a-half-dimensional cases. To numerically test the methodology, the measured ground surface responses are replaced by simulated ones obtained in a set of points called collocation points. In this context, a parametric study has been developed with the aim of finding out a robust criterion for the application of the present methodology with respect to the amount and location of the collocation points (representing vibration sensors) and virtual forces. It is found that the distance between virtual sources should be smaller than the S-wave wavelength of the upper soil layer corresponding to the highest frequency of the frequency range of interest to ensure the reliability of the methodology. Moreover, the proposed method is found to be insignificantly affected by the building-tunnel dynamic coupling for building-tunnel distances above 20 m. The proposed hybrid model would simplify the usual numerical prediction approach commonly ado, This work was financially supported by: • Base Funding - UIDB/04708/2020 and Programmatic Funding - UIDP/04708/2020 of the CONSTRUCT - Instituto de I&D em Estruturas e Construç˜oes - funded by national funds through the FCT/MCTES (PIDDAC) and by “Institute for sustainability and innovation in structural engineering” - ISISE (UIDP/04029/2020), funded by the Fundaç˜ao para a Ciˆencia e a Tecnologia (FCT), I.P., and Regional Operational Programme CENTRO2020 within the scope of project CENTRO-01- 0145-FEDER-000006. • The project NVTRail: Noise and Vibrations induced by railway traffic in tunnels: an integrated approach, funded by FEDER funds through COMPETE2020 and by national funds (PIDDAC) through FCT/ MCTES, with grant reference POCI-01-0145-FEDER-029577. • The project VIBWAY: Fast computational tool for railway-induced vibrations and re-radiated noise assessment, with reference RTI2018- 096819-B-I00, supported by the Ministerio de Ciencia e Innovación, Retos de Investigación 2018. This work was partially carried out under the framework of In2Track2, a research project of Shift2Rail (H2020). The financial support provided by University of Leeds Cheney Award Scheme is also appreciated, Postprint (published version)

This paper is concerned with a new prediction methodology for longitudinally invariant soil-structure interaction problems in elastodynamics. The method uses the finite-element method to model the structure, the boundary-element method to model the local soil surrounding the structure and the method of fundamental solutions to model the wave propagation through the soil, all of them formulated in the two-and-a-half dimensional domain. The proposed method firstly obtains the displacement field on the soil-structure interaction boundary making use of a two-and-a-half dimensional coupled finite element–boundary element method. The method of fundamental solutions is used then as a post-processing tool to compute the response of the soil, increasing the computational efficiency of the overall methodology with respect to a methodology that considers the boundary element method as a model of the wave propagation through the soil. The accuracy of the methodology is verified for four calculation examples: a solid cylinder and a circular thin shell embedded in a homogeneous full-space and also in a homogeneous half-space. This verification is performed comparing the results with available analytical or semi-analytical solutions and a conventional two-and-a-half dimensional coupled finite element–boundary element method. Furthermore, a control methodology to increase the robustness of the method is presented., Peer Reviewed, Postprint (published version)

© 2020 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting /republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works, Control stations of a water distribution system monitor several variables such as the pressure, the flow, and the quality of water. For these monitoring tasks, wireless sensor networks with ultra-low power consumption powered by vibration-based energy harvesters as an alternative to the usage of batteries or wired connections might be a suitable option in these facilities. This article investigates the potential applicability of an electromagnetic vibration energy harvester prototype in different control valves of a water distribution system in the province of Barcelona by means of experimental measurements and numerical simulations. The low-amplitude vibration with random excitation is measured with piezoelectric accelerometers in three control valves under normal operating conditions to process each signal and determine the dominant frequency in the complete spectrum, which is found to be in the order of magnitude of kHz, and the dominant frequency in the range of 10 to 100 Hz, where commercial harvesters normally operate. Numerical simulations of the harvester prototype are conducted in all cases with the same materials, geometries, and coil parameters, generating a maximum RMS load voltage and output power when the harvester’s natural frequency matches the dominant frequencies of each vibration signal. The maximum output power estimated in these simulations is 1573.04 nW with a corresponding RMS load voltage of 53.6 mV and optimal load resistance of 1830 O ., Peer Reviewed, Postprint (author's final draft)

The uncertainty assessment of ground-borne noise and vibration predictions is important to reduce risks when decisions are made based on simulation results. In addition, it provides robustness to the prediction framework that could potentially be used for virtual validation of proposals to reduce noise and vibration induced by railway infrastructures. In this work, a general methodology for prediction uncertainty assessment based on the guide to the expression of uncertainty in measurements is applied to a numerical model dedicated to predict the vibration induced by train traffic in tunnels with slab track with isolated blocks. The standard uncertainty of the predicted acceleration on the tunnel wall is obtained by combining the standard uncertainty of the model inputs: sprung and unsprung axle mass, primary suspension and fasteners stiffness and isolated blocks mass and stiffness. The input uncertainty is defined according to the guidance given in international standards, published work or by experience judgement. The sensitivity factors are obtained as the slope of the function that fits the results obtained by running the simulations for a given range of the input quantities. The proposed methodology provides the uncertainty of the result and the contribution of each input to that uncertainty, Postprint (published version)

This paper aims to introduce a computationally efficient and user-friendly toolbox, called VIBWAY, able to predict vibration levels that a future railway line, either at-grade or underground, will generate on its nearby buildings or that an existing line will induce on a new building or facility. The VIBWAY toolbox consist of two modules: the first module is based on a semi-analytical approach to model railway infrastructure; the second module is based on a database of pre-calculated tunnel-soil or at-grade track-soil vibration propagation models using numerical methods and employing machine learning approach to make a scoping model. In the first module, different ballasted and ballastless tracks are modelled. The soil is modelled as an elastic layered half-space, and the tunnel is modelled using thin shell theory. It is assumed that near-field dynamic behaviour of the tunnel-soil system is only influenced by the dynamics of the tunnel and the layer that contains it. The train is modelled as a three-dimensional multi rigid body system. A semi-analytical model of the building which considers the three-dimensional nature of the building structure is used. The first module of the toolbox is of great use when the application of vibration countermeasures is required to address the problem of an unacceptable level of vibrations in the buildings close by existing railway lines. It is advantageous as it can be used to assess the performance of vibration countermeasures applied at the track, and/or the building. The second module of the toolbox is more applicable for general scoping studies of new railway lines crossing dense urban cities and it can only present a general overview of the effect of countermeasures applied on the track. This module is not explained here in detail since it is still in development, Postprint (published version)

In this paper, a comprehensive numerical approach for modelling track/tunnel/soil systems in the context of ground-borne railway-induced vibration problems considering a full-space model of the soil is proposed. All the approach is formulated in the wavenumber-frequency domain and it consists of a coupled finite element–boundary element model of the tunnel/soil system, a semi-analytical model of the track, a multibody model for the vehicle and a model for the vibration propagation in the soil based on semi-analytical solutions of a cylindrical cavity in a full-space. This comprehensive approach has been developed with the aim of computing the vibration energy flow radiated upwards by underground railway tunnels. An axisymmetric formulation to deal with circular underground railway tunnels is included in the approach in order to improve the computational speed of the methodology. This formulation can also be used for other types of railway tunnels if a circular boundary of the boundary element mesh is considered. Since this methodology uses finite elements to model the tunnel structure, its modelling detail is higher than the previously developed methodologies dedicated to compute the vibration energy flow radiated by underground railway infrastructures, since they are based on semi-analytical modelling of the tunnel structure. The present methodology has been specifically designed to be used in general assessment studies about ground-borne underground railway-induced vibrations where decisions on the type of track and/or the application of mitigation measures at the source, as soft rail-pads, under-ballast or under-slab mats, have to be made. Moreover, this methodology can be used for the study of the vibration radiation patterns of railway tunnels., Peer Reviewed, Postprint (published version)

This paper focuses on the bogie-carbody nonlinear dynamic interaction of a Shinkansen high-speed rail vehicle. The Euler-Bernoulli beam model is used to simulate vertical elastic vibrations of the carbody. As a novelty, the traction rod that connects the bogie frame and the carbody is considered a nonlinear element. The equivalent linearization method is used to analyze the nonlinear vehicle system in the frequency domain. The analytical spectrum solution was compared with the measured data from the running test and the numerical solution in the time domain. When the dynamic interaction due to the carbody’s flexibility is considered as nonlinear rather than linear, the maximum amplitude of the bounce acceleration relevant to the first bending mode increases by 38.2 percent at a travel speed of 300 km/h. Ride comfort improvement can be achieved with the inclusion of the nonlinear interaction. It is also feasible to manipulate the vehicle’s ride comfort by altering its bogie-base, The authors gratefully acknowledge precious remarks and valuable propositions from Professor Takahiro Tomioka during this research. The third author would also like to acknowledge the funds provided by the NVTRail project (Noise and Vibrations induced by railway traffic in tunnels: an integrated approach), funded by FEDER funds through COMPETE2020 and by national funds (PIDDAC) through FCT/MCTES, with grant reference POCI-01-0145-FEDER-029577; and by the VIBWAY project (Fast computational tool for railwayinduced vibrations and re-radiated noise assessment), with reference RTI2018-096819-B-I00, supported by the Ministerio de Ciencia e Innovación, Retos de Investigación 2018, Postprint (author's final draft)

This paper presents a study of the efficiency of isolated concrete blocks as vibration mitigation measures for railway-induced ground-borne vibration problems in subway metro tunnels. The study is performed numerically, using a 2.5D FEM-BEM model of the tunnel-soil system, a semi-analytical model of the track and a rigid multibody model of the vehicle. This comprehensive model of the train-track-tunnel-soil system is used to simulate the vibration response at the tunnel wall due to train traffic for two different track types: a slab track with isolated concrete blocks and a slab track with direct fastening systems. For the slab track with isolated concrete blocks case, various values for the under-block pad stiffness and block mass are considered in the simulation in order to study the effect of these parameters on the mitigation efficiency of this solution. To quantify this efficiency, the criterion used is the insertion loss of the maximum transient vibration value at the tunnel wall for the slab track with isolated blocks with respect to the slab track with direct fastening systems. The results show two important outcomes: on one hand, the mass of the blocks has no significant influence; on the other hand, quite low stiffness of the under-block pads is required to achieve significant vibration mitigation benefits with respect to direct fastening systems, Postprint (published version)

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, Postprint (author's final draft)

In this paper, a new prediction methodology to deal with longitudinally invariant soil-structure interaction problems in elastodynamics is presented. The method uses the finite-element method to model the structure, the boundary-element method to model the local soil surrounding the structure and the method of fundamental solutions to model the wave propagation through the soil. All those methods are formulated in the two-and-a-half-dimensional domain. The methodology is firstly verified in the framework of a homogeneous half-space system by comparing the results of the current method with those computed by the semi-analytical solution of this problem. Secondly, the methodology is verified against a two-and-a-half-dimensional finite element-boundary element approach, for two calculation examples: a tunnel embedded in a homogeneous half-space and a tunnel embedded in a layered half-space. This comparison also shows that this novel methodology reduces the computational costs of such simulations without compromising the accuracy of the results. The increase on the computational efficiency is due to the use of the method of fundamental solutions to account for the wave propagation in the medium, and it is even higher when the number of evaluation points increases., Peer Reviewed, Postprint (published version)

The assessment of the dynamic behaviour of resilient elements can be performed using the indirect method as described in the standard ISO 10846-3. This paper presents a methodology for control the error on the estimation of the frequency response functions (FRF) required for the application of the indirect method when sweep sine excitation is used. Based on a simulation process, this methodology allows for the design of the sweep sine excitation parameters, i.e., the sweep rate and the force amplitude, to control three types of errors associated to the experimentally obtained FRF in the presence of background noise: a general error of the FRF in a selected frequency range, and the errors associated to the amplitude and the frequency of the FRF resonance peak. The signal processing method used can be also tested with this methodology. The methodology has been tested in the characterisation of two different resilient elements: an elastomer and a coil spring. The simulated error estimations has been found to be in good agreement with the errors found in the measured FRF. Furthermore, it is found that for large signal-to-noise ratios, both sweep rate and force amplitude significantly affect the FRF estimation error, while, for small signal-to-noise ratios, only the force amplitude can control the error efficiently. The current methodology is specially interesting for laboratory test rigs highly used for the dynamic characterisation of resilient elements which are required to operate efficiently, since it can be used for minimising test times and providing quality assurance. Moreover, the application of this methodology would be specially relevant when characterisation is done in noisy environments, Postprint (published version)