Estudo Geralhttps://estudogeral.sib.uc.ptThe DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material.Sat, 11 Jul 2020 18:09:33 GMT2020-07-11T18:09:33Z50251Prediction of airborne sound and impact sound insulation provided by single and multilayer systems using analytical expressionshttp://hdl.handle.net/10316/3964Title: Prediction of airborne sound and impact sound insulation provided by single and multilayer systems using analytical expressions
Authors: Tadeu, A.; Pereira, A.; Godinho, L.; António, J.
Abstract: In this work, the authors use analytical solutions to assess the airborne sound and impact insulation provided by homogeneous partitions that are infinite along their plane. The algorithm uses Green's functions, derived on the basis of previous work by the authors on the prediction of airborne sound insulation provided by single and double panels. The model is now extended to handle multilayer systems, allowing the simulation of three-dimensional loads applied in both the acoustic and solid media.
Mon, 01 Jan 2007 00:00:00 GMThttp://hdl.handle.net/10316/39642007-01-01T00:00:00ZThe simulation of 3D elastic scattering produced by thin rigid inclusions using the traction boundary element methodhttp://hdl.handle.net/10316/3970Title: The simulation of 3D elastic scattering produced by thin rigid inclusions using the traction boundary element method
Authors: Tadeu, António; Mendes, Paulo Amado; António, Julieta
Abstract: A mixed formulation that uses both the traction boundary element method (TBEM) and the boundary element method (BEM) is proposed to compute the three-dimensional (3D) propagation of elastic waves scattered by two-dimensional (2D) thin rigid inclusions. Although the conventional direct BEM has limitations when dealing with thin-body problems, this model overcomes that difficulty. It is formulated in the frequency domain and, taking into account the 2-1/2D configuration of the problem, can be expressed in terms of waves with varying wavenumbers in the zdirection, kz. The elastic medium is homogeneous and unbounded and it should be noted that no restrictions are imposed on the geometry and orientation of the internal crack.
Sun, 01 Jan 2006 00:00:00 GMThttp://hdl.handle.net/10316/39702006-01-01T00:00:00ZResponse of clamped structural slabs subjected to a dynamic point load via BEMhttp://hdl.handle.net/10316/4007Title: Response of clamped structural slabs subjected to a dynamic point load via BEM
Authors: António, J.; Tadeu, A.; Simões, N.
Abstract: This work computes the response of clamped slabs when subjected to spatially sinusoidal harmonic line loads via the Boundary Element Method (BEM). The formulation uses 2.5D Green's functions for the steady state response of a homogeneous three-dimensional free solid layer formation of infinite extent, proposed earlier by the authors. The inclusion of these Green's functions in the BEM formulation avoids the discretization of free horizontal surfaces, which contributes to the efficiency of the BEM model. Frequency and time responses have been computed for slabs with and without lateral confinements, for different thickness and varying spatially sinusoidal harmonic line loads.
Wed, 01 Jan 2003 00:00:00 GMThttp://hdl.handle.net/10316/40072003-01-01T00:00:00ZThe scattering of 3D sound sources by rigid barriers in the vicinity of tall buildingshttp://hdl.handle.net/10316/4013Title: The scattering of 3D sound sources by rigid barriers in the vicinity of tall buildings
Authors: Godinho, L.; António, J.; Tadeu, A.
Abstract: The acoustic scattering of a three-dimensional (3D) sound source by an infinitely long rigid barrier in the vicinity of a tall building is analyzed using the boundary element method (BEM). The acoustic barrier is modeled using boundary elements, and is assumed to be non-absorbing, while the image source method is used to model the tall building as an infinite vertical barrier. A frequency domain BEM formulation is used, and time domain responses are then obtained by applying an inverse Fourier transformation.
Tue, 01 Jan 2002 00:00:00 GMThttp://hdl.handle.net/10316/40132002-01-01T00:00:00ZSound pressure level attenuation provided by thin rigid screens coupled to tall buildingshttp://hdl.handle.net/10316/3959Title: Sound pressure level attenuation provided by thin rigid screens coupled to tall buildings
Authors: Tadeu, A.; António, J.; Mendes, P. Amado; Godinho, L.
Abstract: This paper computes the sound pressure attenuation provided by thin rigid screens placed on the walls of a tall building to protect the building from the direct sound incidence produced by sound pressure sources placed in its vicinity. The problem is formulated in the frequency domain via the Traction Boundary Element Method (TBEM), which overcomes the thin-body difficulty arising with the classical Boundary Element Method (BEM) formulation. The building, the screens and the ground are assumed to be infinitely long and rigid. The Green's functions used in the TBEM formulation allow the solution to be obtained without discretizing the flat solid ground and vertical solid façade. Thus, only the boundary of each rigid screen is modelled, which allows the TBEM to be efficient even at high excitation frequencies. The hypersingular integrals that result from the implementation of the TBEM are computed analytically. The algorithm is verified using a BEM model, which incorporates the Green's functions for a full space, thus requiring the full discretization of the domain. The model developed is then used to simulate wave propagation in the vicinity of thin rigid screens with different dimensions and geometries. The two-dimensional (2D) and three-dimensional (3D) time and frequency responses and sound pressure attenuation results are both computed over grids of receivers placed perpendicular and parallel to the building wall.
Mon, 01 Jan 2007 00:00:00 GMThttp://hdl.handle.net/10316/39592007-01-01T00:00:00Z3D elastic wave propagation modelling in the presence of 2D fluid-filled thin inclusionshttp://hdl.handle.net/10316/3977Title: 3D elastic wave propagation modelling in the presence of 2D fluid-filled thin inclusions
Authors: Tadeu, António; Mendes, Paulo Amado; António, Julieta
Abstract: In this paper, the traction boundary element method (TBEM) and the boundary element method (BEM), formulated in the frequency domain, are combined so as to evaluate the 3D scattered wave field generated by 2D fluid-filled thin inclusions. This model overcomes the thin-body difficulty posed when the classical BEM is applied. The inclusion may exhibit arbitrary geometry and orientation, and may have null thickness. The singular and hypersingular integrals that appear during the model's implementation are computed analytically, which overcomes one of the drawbacks of this formulation. Different source types such as plane, cylindrical and spherical sources, may excite the medium. The results provided by the proposed model are verified against responses provided by analytical models derived for a cylindrical circular fluid-filled borehole.
Sun, 01 Jan 2006 00:00:00 GMThttp://hdl.handle.net/10316/39772006-01-01T00:00:00ZThe use of monopole and dipole sources in crosswell surveyinghttp://hdl.handle.net/10316/3983Title: The use of monopole and dipole sources in crosswell surveying
Authors: António, Julieta; Tadeu, António
Abstract: This paper implements a boundary element method (BEM) solution, formulated in the frequency domain, to simulate the crosswell S wave surveying technique. In this technique, one fluid-filled borehole hosts the source, and the other the receivers. The system is excited by a monopole or a dipole source placed near the first wall of the borehole wall, while the pressure field is recorded in the second borehole. The three-dimensional solution is computed as a summation of 2.5D solutions for different axial wave numbers.This model is used to assess the influence of the distance between boreholes and the material properties of the medium on the pressure field generated in the second borehole. Slow and fast formations are both simulated. It was found that the responses recorded the contribution of the non-dispersive body waves (the dilatational (P) and shear (S) waves) as well as the effect of dispersive waves associated with different wave modes. The final time solutions are thus intricate, exhibiting wave patterns that may make it difficult to interpret the arrival times of the refracted P and S waves.
Thu, 01 Jan 2004 00:00:00 GMThttp://hdl.handle.net/10316/39832004-01-01T00:00:00ZApplications of the Green Functions in the Study of Acoustic Problems in Open and Closed Spaces.http://hdl.handle.net/10316/4030Title: Applications of the Green Functions in the Study of Acoustic Problems in Open and Closed Spaces.
Authors: Tadeu, A.; António, J.; Godinho, L.
Abstract: This paper presents a set of analytical solutions (Green functions) for the steady state response of a homogenous acoustic three-dimensional space subjected to a point harmonic load or a spatially sinusoidal harmonic line load. The propagation medium is modelled with plane surfaces placed so as to reproduce spaces that vary from a simple half-space to a rectangular parallelepiped closed space. The final expressions are implemented to evaluate first the pressure field inside a rectangular parallelepiped room, whose walls allow different absorption coefficients. Then, the acoustic scattering of a three-dimensional sound source by an infinitely long rigid barrier in the vicinity of a tall building is evaluated using the boundary-element method (BEM), making use of the analytical solution for a spatially sinusoidal line source. The use of these Green functions allows the required BEM discretization to be limited to the surface of the barrier, avoiding the discretization of the tall building and ground. The calculations are performed in the frequency domain and time signatures are obtained by means of inverse Fourier transforms. Complex frequencies are used to attenuate the response at the end of the time frame, which is taken into account by rescaling the time response.
Mon, 01 Jan 2001 00:00:00 GMThttp://hdl.handle.net/10316/40302001-01-01T00:00:00ZAcoustic insulation provided by circular and infinite plane wallshttp://hdl.handle.net/10316/3990Title: Acoustic insulation provided by circular and infinite plane walls
Authors: António, Julieta; Godinho, Luís; Tadeu, A.António
Thu, 01 Jan 2004 00:00:00 GMThttp://hdl.handle.net/10316/39902004-01-01T00:00:00ZAnalytical evaluation of the acoustic insulation provided by double infinite wallshttp://hdl.handle.net/10316/4001Title: Analytical evaluation of the acoustic insulation provided by double infinite walls
Authors: António, J. M. P.; Tadeu, A.; Godinho, L.
Abstract: The acoustic insulation provided by infinite double panel walls, when subjected to spatially sinusoidal line pressure loads, is computed analytically. The methodology used extends earlier work by the authors on the definition of the acoustic insulation conferred by a single panel wall. It does not entail any simplification other than the assumption that the panels are of infinite extent. The full interaction between the fluid (air) and the solid layers is thus taken into account and the calculation does not involve limiting the thickness of any layer, as the Kirchhoff or Mindlin theories require. The problem is first formulated in the frequency domain. Time domain solutions are then obtained by means of inverse Fourier transforms using complex frequencies.
Wed, 01 Jan 2003 00:00:00 GMThttp://hdl.handle.net/10316/40012003-01-01T00:00:00ZGreen's functions for 2.5D elastodynamic problems in a free solid layer formationhttp://hdl.handle.net/10316/4021Title: Green's functions for 2.5D elastodynamic problems in a free solid layer formation
Authors: Tadeu, António; António, Julieta
Abstract: This work presents analytical Green's functions for the steady state response of a homogeneous three-dimensional free solid layer formation (slab) subjected to a spatially sinusoidal harmonic line load, polarized along the horizontal, vertical and z directions. The equations presented here are not only themselves very interesting but are also useful for formulating three-dimensional elastodynamic problems in a slab-type formation, using integral transform methods and/or boundary elements. The final expressions are validated by comparing them with the results obtained by using the Boundary Element Method solution, for which both free surfaces of the slab are discretized with boundary elements.
Tue, 01 Jan 2002 00:00:00 GMThttp://hdl.handle.net/10316/40212002-01-01T00:00:00ZUse of constant, linear and quadratic boundary elements in 3D wave diffraction analysishttp://hdl.handle.net/10316/4044Title: Use of constant, linear and quadratic boundary elements in 3D wave diffraction analysis
Authors: Tadeu, A.; António, J.
Abstract: The performance of the Boundary Element Method (BEM) depends on the size of the elements and the interpolation function used. However, improvements in accuracy and efficiency obtained with both expansion and grid refinement increases demand on the computational effort. This paper evaluates the performance of constant, linear and quadratic elements in the analysis of the three-dimensional scattering caused by a cylindrical cavity buried in an infinite homogeneous elastic medium subjected to a point load. A circular cylindrical cavity for which analytical solutions are known is used in the simulation analysis. First, the dominant BEM errors are identified in the frequency domain and related to the natural vibration modes of the inclusion. Comparisons of BEM errors are then made for different types of boundary elements, maintaining similar computational costs. Finally, the accuracy of the BEM solution is evaluated when the nodal points are moved inside linear and quadratic discontinuous elements.
Sat, 01 Jan 2000 00:00:00 GMThttp://hdl.handle.net/10316/40442000-01-01T00:00:00Z3D scattering of waves by a cylindrical irregular cavity of infinite length in a homogeneous elastic mediumhttp://hdl.handle.net/10316/4020Title: 3D scattering of waves by a cylindrical irregular cavity of infinite length in a homogeneous elastic medium
Authors: Tadeu, António J. B.; António, Julieta M. P.; Kausel, Eduardo
Tue, 01 Jan 2002 00:00:00 GMThttp://hdl.handle.net/10316/40202002-01-01T00:00:00ZSound propagation around rigid barriers laterally confined by tall buildingshttp://hdl.handle.net/10316/4016Title: Sound propagation around rigid barriers laterally confined by tall buildings
Authors: Godinho, Luís; António, Julieta; Tadeu, António
Abstract: This paper focuses on the propagation of sound waves in the presence of acoustic barriers placed close to very tall buildings. The boundary element method (BEM) is used to model the acoustic barrier, while the presence of the tall buildings is taken into account by using the image source method. Different geometries are analyzed, representing the cases of a single building, two buildings forming a corner and three buildings defining a laterally confined space. The acoustic barrier is assumed to be non-absorbing, and all the buildings and the ground are modeled as infinite rigid plane surfaces. Calculations are performed in the frequency domain and time signals are then obtained by means of Inverse Fourier Transforms. The sound pressure loss provided by the acoustic barrier is computed, illustrating the importance of the lateral confinements.
Tue, 01 Jan 2002 00:00:00 GMThttp://hdl.handle.net/10316/40162002-01-01T00:00:00ZPropagação de ondas em meios acústicos e elásticos : modelos analíticos e numéricoshttp://hdl.handle.net/10316/1707Title: Propagação de ondas em meios acústicos e elásticos : modelos analíticos e numéricos
Authors: António, Julieta Maria Pires
Abstract: A modelação da propagação de ondas em meios acústicos ou elásticos constitui uma ferramenta de investigação importante na interpretação e previsão de determinados fenómenos físicos. Existem várias áreas do conhecimento que beneficiam destes modelos de análise tais como a engenharia sísmica, a engenharia acústica e as técnicas de análise não destrutiva. O presente trabalho contribui para o desenvolvimento de formulações analíticas e numéricas (Método dos Elementos Fronteira) aplicáveis na modelação da propagação de ondas em meios acústicos e elásticos infinitos ou confinados.
Os algoritmos desenvolvidos foram implementados no domínio da frequência. Respostas no tempo são obtidas através de transformadas inversas de Fourier. Frequências complexas são usadas de modo a evitar fenómenos de "aliasing". Inicialmente desenvolvem-se soluções analíticas que permitem modelar a propagação de ondas em meios contendo inclusões bidimensionais com geometria circular. Estas soluções funcionam como soluções de referência na validação do Método dos Elementos Fronteira (BEM), aplicáveis quando a geometria do problema não é regular. Ao longo desta tese são desenvolvidos algoritmos do BEM que permitem modelar a resposta dinâmica de cavidades e inclusões elásticas cilíndricas, bem como problemas envolvendo a interacção de fluidos com formações sólidas.Depois, desenvolvem-se funções analíticas que permitem definir níveis de pressão sonora em espaços acústicos abertos e fechados. Outras soluções analíticas são aplicadas à propagação de ondas em meios estratificados. Essas soluções permitem determinar num caso os tempos de reverberação em espaços fechados e no outro a redução do nível sonoro conferida por paredes simples e duplas. Além desta aplicação, algumas destas funções analíticas são integradas em algoritmos BEM, desempenhando o papel de funções de Green. Esta dissertação termina simulando a propagação de ondas em meios contendo inclusões e irregularidades, através do BEM, o que permite definir características da propagação de ondas utilizáveis em métodos de análise não destrutiva.
Description: Tese de doutoramento em Engenharia Civil (Construções) apresentada à Fac. de Ciências e Tecnologia da Univ. de Coimbra
Thu, 20 Jun 2002 00:00:00 GMThttp://hdl.handle.net/10316/17072002-06-20T00:00:00ZThermal delay provided by floors containing layers that incorporate expanded cork granule wastehttp://hdl.handle.net/10316/27483Title: Thermal delay provided by floors containing layers that incorporate expanded cork granule waste
Authors: Tadeu, A.; Moreira, A.; António, J.; Simões, N.; Simões, I.
Abstract: This paper reports the computation of the thermal delay provided by concrete floors built with layers of cork and lightweight screed that incorporate expanded cork granule waste. The heat transfer by conduction across these multilayer systems is simulated analytically under unsteady boundary conditions.
The thermal delay is computed for multilayer concrete floors with varying numbers of layers and layer thicknesses. The mass density and thermal conductivity of the various materials were determined experimentally. Given its heterogeneity, the specific heat of the lightweight screed was obtained indirectly using both the experimental results and the analytical model.
The results obtained show the potential of these composites in applications for increasing the thermal performance of concrete floors, in particular the thermal delay and thermal resistance. The results show that the contribution of the insulating lightweight screed material's properties to thermal delay is more relevant in systems composed of few layers. The constructive solutions composed of a greater number of layers present higher thermal delay value.
Wed, 01 Jan 2014 00:00:00 GMThttp://hdl.handle.net/10316/274832014-01-01T00:00:00ZA three-dimensional acoustics model using the method of fundamental solutionshttp://hdl.handle.net/10316/3951Title: A three-dimensional acoustics model using the method of fundamental solutions
Authors: António, Julieta; Tadeu, António; Godinho, Luís
Abstract: The method of fundamental solutions (MFS) is formulated in the frequency domain to model the sound wave propagation in three-dimensional (3D) enclosed acoustic spaces. In this model the solution is obtained by approximation, using a linear combination of fundamental solutions for the 3D Helmholtz equation. Those solutions relate to a set of virtual sources placed over a surface placed outside the domain in order to avoid singularities. The materials coating the enclosed space surfaces can be assumed to be sound absorbent. This effect is introduced in the model by imposing impedance boundary conditions, with the impedance being defined as a function of the absorption coefficient. To impose these boundary conditions, a set of collocation points (observation points) needs to be selected along the boundary.
Tue, 01 Jan 2008 00:00:00 GMThttp://hdl.handle.net/10316/39512008-01-01T00:00:00ZAcoustic insulation of single panel walls provided by analytical expressions versus the mass law.http://hdl.handle.net/10316/4012Title: Acoustic insulation of single panel walls provided by analytical expressions versus the mass law.
Authors: Tadeu, A.; António, J. M. P.
Abstract: Analytical solutions are presented for the calculation of the acoustic insulation provided by an infinite single panel wall when subjected to a spatially sinusoidal harmonic line load or a point pressure load (modelled as a superposition of spatially sinusoidal harmonic line loads). The method used does not entail limiting the thickness of the layer, as the Kirchhoff or Mindlin theory requires, and fully takes into account the coupling between the fluid (air) and the solid panel. All calculations are performed in the frequency domain. Time signatures are obtained by means of inverse Fourier transforms. Special attention is given to the limitations of the simplified models, which are not able to predict dips of insulation such as that due to the coincidence effect. It has been shown that, although time results may appear complicated, the arrival of various pulses at the receivers can be understood in terms of the travelling body pulses and guided waves. Simulated results have been computed for ceramic, concrete and glass walls of different thickness, when subjected to plane, linear and spherical waves. The insulation computed was found to be highly dependent on receiver position, given the interaction between the incident wave field and the directed reflected field on the wall, when the wall is struck by a cylindrical or a spherical pulse wave.
Tue, 01 Jan 2002 00:00:00 GMThttp://hdl.handle.net/10316/40122002-01-01T00:00:00Z3D scattering by multiple cylindrical cavities buried in an elastic formationhttp://hdl.handle.net/10316/4035Title: 3D scattering by multiple cylindrical cavities buried in an elastic formation
Authors: António, Julieta; Tadeu, António
Abstract: This paper presents the three-dimensional scattering field obtained when multiple cylindrical circular cavities of infinite length buried in a homogeneous elastic medium, are subjected to dilatational point loads placed at some point in the medium. The solution is formulated using boundary elements for a wide range of frequencies and spatially harmonic line loads, which are then used to obtain time series by means of (fast) inverse Fourier transforms into space-time. The method and the expressions presented are implemented and validated by applying them to a cylindrical circular cavity buried in an infinite homogeneous elastic medium subjected to a dilatational point load, for which the solution is calculated in closed form. The boundary elements method is then used to evaluate the wave-field elicited by a dilatational point load source in the presence of a different number of cylindrical oval cavities. Simulation analyses using this idealized model are then applied to the study of wave propagation patterns in the vicinity of these inclusions. The amplitude of the wavefield in the frequency vs axial-wavenumber domain is presented, allowing the recognition, identification, and physical interpretation of the variation of the wavefield.
Mon, 01 Jan 2001 00:00:00 GMThttp://hdl.handle.net/10316/40352001-01-01T00:00:00ZSoluções analíticas para a propagação do som em espaços bidimensionais e tridimensionaishttp://hdl.handle.net/10316/13424Title: Soluções analíticas para a propagação do som em espaços bidimensionais e tridimensionais
Authors: Tadeu, António; António, Julieta; Godinho, Luis
Abstract: Um problema de propagação de ondas de pressão pode ser resolvido com a ajuda de
expressões denominadas funções de Green. Estas funções definem a relação entre variáveis
(pressões e velocidades) em determinado ponto no espaço resultante de variações harmónicas
de pressão (forças) posicionadas algures no meio de propagação. Estas funções são
frequentemente definidas para variações de pressão tridimensionais (forças pontuais) em
espaços infinitos e variações lineares harmónicas de pressão actuando em espaços
bidimensionais. Estas escolhas devem-se à possibilidade da definição analítica deste tipo de
funções. Considerando que a propagação do som se processa na presença de barreiras
perfeitamente reflectoras poderá considerar-se a existência de fontes virtuais posicionadas de
modo a verificarem as condições fronteiras necessárias. Este artigo resume um conjunto
destas soluções para espaços tridimensionais e bidimensionais. Além destas expressões este
artigo apresenta soluções para fontes harmónicas lineares cuja amplitude varia de forma
sinusoidal na terceira dimensão. Este tipo de solução é frequentemente referido como
problema 2 1 2 D , útil no cálculo de soluções tridimensionais através do Método dos
Elementos Fronteira
Sat, 01 Jan 2000 00:00:00 GMThttp://hdl.handle.net/10316/134242000-01-01T00:00:00ZInfluence of the cross-section geometry of a cylindrical solid submerged in an acoustic medium on wave propagationhttp://hdl.handle.net/10316/4019Title: Influence of the cross-section geometry of a cylindrical solid submerged in an acoustic medium on wave propagation
Authors: Pereira, Andreia; Tadeu, António; António, Julieta
Abstract: This paper studies wave propagation in the vicinity of a cylindrical solid formation submerged in an acoustic medium generated by point blast loads placed outside the inclusion. The full 3D solution is obtained first in the frequency domain as a discrete summation of responses for 2D problems defined by a spatial Fourier transform. Each 2D solution is computed using the Boundary Element Method, which makes use of two-and-a-half-dimensional Green's functions. This model is implemented to obtain Fourier spectra responses which make it possible to identify the behavior of both the axisymmetric and non-axisymmetric guided wave modes, when the cross-section of the elastic inclusion changes from circular to smooth oval.
Tue, 01 Jan 2002 00:00:00 GMThttp://hdl.handle.net/10316/40192002-01-01T00:00:00ZAmplification of elastic waves due to a point source in the presence of complex surface topographyhttp://hdl.handle.net/10316/4033Title: Amplification of elastic waves due to a point source in the presence of complex surface topography
Authors: Tadeu, António; Santos, Paulo; António, Julieta
Mon, 01 Jan 2001 00:00:00 GMThttp://hdl.handle.net/10316/40332001-01-01T00:00:00Z2.5D scattering of waves by rigid inclusions buried under a fluid channel via BEMhttp://hdl.handle.net/10316/3981Title: 2.5D scattering of waves by rigid inclusions buried under a fluid channel via BEM
Authors: António, Julieta; Tadeu, António; Godinho, Luís
Abstract: A 2.5D Boundary Element Method (BEM) formulation, applied in the frequency domain, is developed to compute the scattering of waves by rigid inclusions buried in a semi-infinite solid under a fluid layer, when this system is excited by a spatially-sinusoidal harmonic load.
Sat, 01 Jan 2005 00:00:00 GMThttp://hdl.handle.net/10316/39812005-01-01T00:00:00Z3D sound scattering by rigid barriers in the vicinity of tall buildingshttp://hdl.handle.net/10316/4026Title: 3D sound scattering by rigid barriers in the vicinity of tall buildings
Authors: Godinho, L.; António, J.; Tadeu, A.
Abstract: The boundary element method (BEM) is used to evaluate the acoustic scattering of a three-dimensional (3D) sound source by an infinitely long rigid barrier in the vicinity of tall buildings. The barrier is assumed to be non-absorbing and the buildings are modeled as an infinite barrier. The calculations are performed in the frequency domain and time signatures are obtained by means of inverse Fourier transforms. The 3D solution is obtained by means of Fourier transform in the direction in which the geometry does not vary. This requires solving a series of 2D problems with different spatial wavenumbers, kz. The wavenumber transform in discrete form is obtained by considering an infinite number of virtual point sources equally spaced along the z axis. Complex frequencies are used to minimize the influence of these neighboring fictitious sources. Different geometric models, with barriers of varying sizes, are used. The reduction of sound pressure in the vicinity of the buildings is evaluated and the creation of shadow zones by the barriers is analyzed and compared with results provided by a simplified method.
Mon, 01 Jan 2001 00:00:00 GMThttp://hdl.handle.net/10316/40262001-01-01T00:00:00Z3D seismic response of a limited valley via BEM using 2.5D analytical Green's functions for an infinite free-rigid layerhttp://hdl.handle.net/10316/4488Title: 3D seismic response of a limited valley via BEM using 2.5D analytical Green's functions for an infinite free-rigid layer
Authors: António, Julieta; Tadeu, António
Abstract: This paper presents analytical solutions for computing the 3D displacements in a flat solid elastic stratum bounded by a rigid base, when it is subjected to spatially sinusoidal harmonic line loads. These functions are also used as Greens functions in a boundary element method code that simulates the seismic wave propagation in a confined or semi-confined 2D valley, avoiding the discretization of the free and rigid horizontal boundaries.
Tue, 01 Jan 2002 00:00:00 GMThttp://hdl.handle.net/10316/44882002-01-01T00:00:00Z