Ovidiu VASILE
University Politehnica of Bucharest, Department of Mechanics, Department Member
- Ovidiu VASILE was born in May 3, 1978, in Târgovişte, Romania. He graduated Politehnica University of Bucharest in me... moreOvidiu VASILE was born in May 3, 1978, in Târgovişte, Romania. He graduated Politehnica University of Bucharest in mechanical field and received the M.Sc. degree in Vibration Systems and Engineering Acoustics from the Politehnica University of Bucharest, Romania, in 2001. In April 2009, he received the Ph.D. degree from the same university on the subject of modeling noise and vibration control.Dr. Vasile is currently (from October, 2014) Associate Professor, on Department of Mechanics, Politehnica University of Bucharest. Also, from 2004 is involved on various research and experimental study with Research Institute for Construction Equipment and Technology - ICECON, from Bucharest. From 2005 until present is General Secretary of the Romanian Acoustics Society and Managing Editor of the Romanian Journal of Acoustics and Vibration.edit
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Having as starting point the fundamental requirements outlined in Directive 2002/44/CE in which the minimum health and safety requirements for the workers’ exposure to the risks generated by physical agents (vibrations) are established,... more
Having as starting point the fundamental requirements outlined in Directive 2002/44/CE in which the minimum health and safety requirements for the workers’ exposure to the risks generated by physical agents (vibrations) are established, the paper presents a concrete evaluation, based on experimental determinations, of the vibrations transmitted to the entire body of a human operator. The evaluation of the level of exposure to vibrations is based on the computation of the daily exposure, expressed over a period of eight hours. The weighted mean square acceleration will be determined function of the frequency weighting curves Wc, Wd and Wk , using a MATLAB program developed by the author. Based on the indications from SR ISO 2361-1 the evaluation of the vibrations for health, comfort, and perception are presented as experimental results. In this context, the necessity of compliance with the minimum health and safety requirements imposed by the current legislation are highlighted.
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The paper addresses the methodology for obtaining biocomposite structures from waste, with sound-absorbing properties, such as: thuja shells, walnut shells, pistachio shells, beech sawdust, pumpkin seeds shells and sunflower seeds shells.... more
The paper addresses the methodology for obtaining biocomposite structures from waste, with sound-absorbing properties, such as: thuja shells, walnut shells, pistachio shells, beech sawdust, pumpkin seeds shells and sunflower seeds shells. The experimental analysis carried out considers the study of the sound-absorbing properties held by the proposed new biocomposite materials, by determining the value of the sound absorption coefficient, reflection coefficient, impedance ratio, using the Kundt tube. The interpretation of the results obtained from the evaluation of biocomposites shows that they have sound-absorbing properties. Consequently, sound-absorbing panels with soundproofing properties can be made from these materials, which can be used in industry, transportation, construction, etc. as well as for decorative purposes in spaces such as cinemas, malls, spas, etc.
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The aim of this paper is to present an algorithm for computing the fractional Fourier transform integrated into the pipeline of processing multi-variate and distributed data recorded by the engine control unit (ECU) of a car and its... more
The aim of this paper is to present an algorithm for computing the fractional Fourier transform integrated into the pipeline of processing multi-variate and distributed data recorded by the engine control unit (ECU) of a car and its satellites. The role of this transform is vital in establishing a time-variant filter and therefore it must be computed in a fast way. But for large scale time series, the application of the discrete fractional Fourier transform involves the computations of a large number of Hermite polynomials of increasingly order. The parallel algorithm presented will optimally compute the discrete Fourier-type transform for any given angle.
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In this paper, according to the natural frequencies resulted from the simulation for 30 vibration mode shapes of rectangular, square, trapeze and parallelogram plates that are analyzed with the SolidWorks program, the absolute... more
In this paper, according to the natural frequencies resulted from the simulation for 30 vibration mode shapes of rectangular, square, trapeze and parallelogram plates that are analyzed with the SolidWorks program, the absolute respectively the relative variation has been obtained for thin clamped plates with the same area. The absolute and relative variation of natural frequencies was made for 6 possible cases of the 4 type of plates, namely: rectangle-square, trapeze-rectangle, trapeze-square, parallelogram-rectangle, parallelogram-square and trapeze-parallelogram.
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The aim of the paper is to analyze the free vibration of a symmetrical, spatial structure made up of bars, obtained by joining two identical subsystems. It is a real structure, encountered in civil engineering. In the literature, there... more
The aim of the paper is to analyze the free vibration of a symmetrical, spatial structure made up of bars, obtained by joining two identical subsystems. It is a real structure, encountered in civil engineering. In the literature, there are papers that have established vibration properties of structures with symmetry. In the paper, we propose to see if these properties apply to a structure made up by two identical, mirror symmetrical substructures and linked by common elements.
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MIHAI BRATU, OVIDIU DUMITRESCU∗ , OVIDIU VASILE, IOAN ROPOTĂ, LUOANA FLORENTINA PASCU 1 Institutul Naţional de Cercetare – Dezvoltare pentru Ecologie Industrială – ECOIND, Str. Drumul Podu Dâmboviţei Nr. 71-73, Sector 6, 060652,... more
MIHAI BRATU, OVIDIU DUMITRESCU∗ , OVIDIU VASILE, IOAN ROPOTĂ, LUOANA FLORENTINA PASCU 1 Institutul Naţional de Cercetare – Dezvoltare pentru Ecologie Industrială – ECOIND, Str. Drumul Podu Dâmboviţei Nr. 71-73, Sector 6, 060652, Bucureşti, România 2 Universitatea Politehnica Bucureşti, Str. Gheorghe Polizu, Nr. 1-7, Sector 1, 011061, Bucureşti, România 3 Universitatea POLITEHNICA Bucureşti, Departamentul de Mecanică, Splaiul Independenţei nr. 313, Bucureşti, România Liceul Dimitrie Paciurea, Str Băiculești, nr. 29, sector 1, București, Romănia
Research Interests: Acoustics and Attenuation
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Plates known as sound absorbing materials: textiles recovered fabrics plus polyethylene are made layered composite material intended to be used to encapsulate industrial engines, as sources of noise in the production departments.... more
Plates known as sound absorbing materials: textiles recovered fabrics plus polyethylene are made layered composite material intended to be used to encapsulate industrial engines, as sources of noise in the production departments. Influence of thickness sound-absorbing material can be supported by the values obtained for the absorption coefficient, but it can be studied as a study case in the anechoic chamber, where the sound pressure level is measured with a sound level meter. Cases captured: a free engine; the engine placed in a metallic cube and motor inserted; metal cube that was doubled separately with one material and then with the composite material proposed. For each situation are eight determinations on the perimeter of a circle with a radius of one meter from the source of the noise. Plot a graph of experimental results that support the idea: greater thickness of the layer of material will cause a better absorption of noise.
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For sustainable development of the textile industry must find solutions to reduce waste and decrease noise at work. Of textile waste are obtained boards of different thicknesses, which aim to be wide field of use. For it is to achieve... more
For sustainable development of the textile industry must find solutions to reduce waste and decrease noise at work. Of textile waste are obtained boards of different thicknesses, which aim to be wide field of use. For it is to achieve some experimental results about the soundproofing of plate types: is studying recoverable boards made of short textile fiber and cork boards. Textiles have a thickness of 3 mm and 10 mm and cork boards with a thickness of 3 mm and 10 mm. For determining is used the impedance tube reading Brüel&Kjaer, type 4206. By analyzing the absorption coefficient results that materials have absorbing characteristics that increase with material thickness. From these boards aims to obtain laminated composite materials used to encapsulate industrial noise sources.
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In addition to elastomeric devices, viscous fluid dampers can reduce the vibration transmitted to dynamic systems. Usually, these fluid dampers are rate-independent and used in conjunction with elastomeric isolators to insulate the base... more
In addition to elastomeric devices, viscous fluid dampers can reduce the vibration transmitted to dynamic systems. Usually, these fluid dampers are rate-independent and used in conjunction with elastomeric isolators to insulate the base of buildings (buildings, bridges, etc.) to reduce the shocks caused by earthquakes by increasing the damping capability. According to the EN 15129 standard, the velocity-dependent anti-seismic devices are Fluid Viscous Dampers (FVDs) and Fluid Spring Dampers (FSDs). Based on experimental data from a dynamic regime of a fluid viscous damper of small dimensions, for which not all the design details are known, to determine the law of behavior for the viscous damper, the characteristics of the damper are identified, including the nonlinear parameter α (exponent of velocity V) of the constitutive law. Note that the magnitude of the fluid damper force depends on both velocity (where the maximum value is 0.52 m/s) and amplitude displacement (±25 mm). Using ...
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Sound-absorbing panels made with a perforated front and a sound-absorbing material on the back have been used in many forms of construction for a long time. It is a reasonably efficient system, obtaining high values of sound absorption at... more
Sound-absorbing panels made with a perforated front and a sound-absorbing material on the back have been used in many forms of construction for a long time. It is a reasonably efficient system, obtaining high values of sound absorption at a specific resonant frequency, depending on the design of the structure of the sound-absorbing multilayer panel. The present work considers an acoustic panel in two constructive types, consisting of four layers: a front panel made of perforated sheet, polyethylene foam foil, basalt wool board with two different thicknesses, and a back panel of the non-perforated sheet. Due to the different thicknesses of the basalt wool board, for the multilayer structure of the acoustic panel, differences in acoustic impedance and acoustic absorption can be highlighted, experimentally determined with an impedance tube, using the transfer function method (TFM) based on EN ISO 10534-2 in the frequency range 100–3200 Hz. In the meantime, a method was developed to pre...
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The aim of this work is to obtain new materials with improved sound absorbing and thermal properties, using rigid or flexible polyurethane foam reinforced with recycled fir sawdust from wood processing as well as by optimizing their... more
The aim of this work is to obtain new materials with improved sound absorbing and thermal properties, using rigid or flexible polyurethane foam reinforced with recycled fir sawdust from wood processing as well as by optimizing their mixing ratio. In this respect, we prepared and characterized samples by mixing rigid polyurethane foam (RPUF)/flexible polyurethane foam (FPUF) with 0, 35, 40, 45, and 50 wt% fir sawdust (FS) with grains size larger than 2 mm. The samples were evaluated by cell morphology analysis, sound absorption, and thermal insulation performance. The obtained composite materials containing 50% sawdust have superior acoustic properties compared to those with 100% FPUF in the range of 420–1250 Hz. The addition of 35% and 50% FS in the FPUF matrix led to improved thermal insulation properties and decreased thermal insulation properties in the case of RPUF. The results show that the use of FS-based composites with the FPUF/RPUF matrix for sound absorption and thermal in...
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The guided ultrasonic waves have become interesting alternatives to classical pulse-echo nondestructive testing in industrial piping systems. These guided waves have the capability to travel for several meters along pipes, bringing back... more
The guided ultrasonic waves have become interesting alternatives to classical pulse-echo nondestructive testing in industrial piping systems. These guided waves have the capability to travel for several meters along pipes, bringing back to the emitting transducer information about possible defects. For this reason, researches were conducted in many laboratories of the world for the last decades. In our country such preoccupation is relatively recent. Benefiting from a national research project, our team has also developed original software to solve the dispersion curves of tubes. These dispersion curves provide the travel velocity of the guided waves, which are functions of frequency. In most cases, for a given frequency, there are many propagating waves with specific stress-displacements patterns, which are called guides modes. Using these velocities, the experimentalist can adjust the receiver to detect the selected mode, which can be used to detect defects. The present paper pres...
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The paper analyzes the possibility of determining the acoustic absorption coefficient by means of mathematical models from the literature for new composite porous materials. The materials studied were made of fir sawdust and flexible... more
The paper analyzes the possibility of determining the acoustic absorption coefficient by means of mathematical models from the literature for new composite porous materials. The materials studied were made of fir sawdust and flexible polyurethane foam with open pores. The acoustic absorption coefficient of the materials was determined experimentally by means of the impedance tube. The experimental results were compared with those obtained by modeling with the Maple 16 software, by inserting the material characteristics into the mathematical equations. The models used in this study were Delanz-Bayley adapted for foams, Allard-Champoux and Hamet-Berengeir. The results of this study show that the analyzed models are not suitable for new composite porous materials and that new models should be developed to correctly describe their acoustic absorption properties.
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The acoustic comfort includes the protection against noise and it is closely related to the sound absorption concept. This paper presents an experimental study on sound absorption coefficients, for some composite materials: waste... more
The acoustic comfort includes the protection against noise and it is closely related to the sound absorption concept. This paper presents an experimental study on sound absorption coefficients, for some composite materials: waste materials (rubber crumbs, textile, flax fibers) mixed with rigid polyurethane foam as binder. The composite materials were characterized both acoustically (sound absorption coefficient) and also in terms of heat transfer (thermal conductivity). The acoustic absorption coefficient was determined using the impedance tube and the influence of structure of these materials on the sound absorbing properties was analyzed. The experimental results show the sound absorption performances of some composites based on recycled waste materials, thus promoting environmentally friendly solutions.
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Abstract: Even it has been recognized that Shape Memory Alloys have a significant potential for deployment actuators, the number of applications of SMA-based actuators to the present day is still quite small, due to the need of deep... more
Abstract: Even it has been recognized that Shape Memory Alloys have a significant potential for deployment actuators, the number of applications of SMA-based actuators to the present day is still quite small, due to the need of deep understanding of the thermomechanical behavior of SMA. SMAs offer attractive potentials such as: reversible strains of several percent, generation of high recovery stresses and high power/weight ratios. This paper tries to provide an overview of the shape memory functions. A table with property values for ...
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Abstract: Buildings can be affected by vibrations if theirs parameters outgrow certain limits. The nature of the damage is given by the value of this parameters (displacement, velocity or acceleration). The paper pre-sents reference... more
Abstract: Buildings can be affected by vibrations if theirs parameters outgrow certain limits. The nature of the damage is given by the value of this parameters (displacement, velocity or acceleration). The paper pre-sents reference values adopted in different countries regarding the maximum admitted level of vibrations.
Abstract:-This paper presents the researches made by the authors in order to develop an algorithm and method to localize damages in beams using vibration measurement. The chosen type of beam was the cantilever one, for which a database... more
Abstract:-This paper presents the researches made by the authors in order to develop an algorithm and method to localize damages in beams using vibration measurement. The chosen type of beam was the cantilever one, for which a database containing the first ten natural frequencies in undamaged state was realized. Afterwards, eight points relevant for the characterization of the beam's dynamic behavior were determined by analytical calculus. The database was completed with the first ten natural frequencies of the beam damaged ...
Guardrails are systems designed to keep vehicles in certain places, by preventing access in dangerous areas. They can be a source of injuries because their rigid structure, designed to face high level of strength. Depending on their speed... more
Guardrails are systems designed to keep vehicles in certain places, by preventing access in dangerous areas. They can be a source of injuries because their rigid structure, designed to face high level of strength. Depending on their speed and mass, vehicles can load guardrails in various forms. The authors propose the use of adaptive guardrails, involving polymers, which react different by different load levels. The behaviour is studied using modeling and simulation with the FEM; different types of guardrails and external loads ...
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The paper presents an algorithm to assess damages in composite structures, based on how natural frequencies of weak-axes bending vibration modes change due to damage. The authors have contrived a correlation between the strain energy... more
The paper presents an algorithm to assess damages in composite structures, based on how natural frequencies of weak-axes bending vibration modes change due to damage. The authors have contrived a correlation between the strain energy stored in a segment of a beam-like structure and the frequency change for that mode if damage occurs on that segment. Finding that the dynamic behavior of composite structures can be best modeled using the share model, which consider the bending moment together with lateral ...
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Abstract: We propose an adaptive method for the analysis of the dynamical changes in mechanical structures. Using measurement techniques and the flexible Gabor-wavelet transform, we perform an optimal denoising of slowly variable... more
Abstract: We propose an adaptive method for the analysis of the dynamical changes in mechanical structures. Using measurement techniques and the flexible Gabor-wavelet transform, we perform an optimal denoising of slowly variable band-limited signals for an improved mechanical structure fault diagnostics.
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Noise is a well known source of environmental pollution in urban areas or at work. Sound pressure level has a harmful effect on human health. In this paper we present our research on making a new type of composite material and testing its... more
Noise is a well known source of environmental pollution in urban areas or at work. Sound pressure level has a harmful effect on human health. In this paper we present our research on making a new type of composite material and testing its properties of noise attenuation level. Tests were carried out in the anechoic chamber using barrier attenuators of sound waves made of composite material consisting of 50% formaldehyde resin reinforced polypropylene granules formed from waste 50%. It was also determined the efficiency of the panel by calculating the diffraction pression according to the sound waves dispersion on the acoustic panel's surface and mapping the attenuation of noise levels due to the composite material.. Zgomotul este o sursă bine cunoscută de poluare a mediului din zonele urbane sau la locul de muncă. Nivelul de presiune sonoră produce efecte nocive asupra sănătăţii oamenilor. În această lucrare sunt prezentate cercetări efectuate privind elaborarea unui nou tip de ...
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Non-destructive inspection of long pipes can be time consuming and some localized defects might remain undetected. A new technique based on guided waves was developed in the last decade. High risk industries such as chemical or nuclear,... more
Non-destructive inspection of long pipes can be time consuming and some localized defects might remain undetected. A new technique based on guided waves was developed in the last decade. High risk industries such as chemical or nuclear, require a reliable method covering if possible the whole length of the piping. Guided ultrasonic waves can propagate along several meters and up to tens of meters in pipes. The reflected signal, which is usually made of some of the propagating modes, brings information concerning the presence of defects and in some conditions on their location and size. There are three classes of guided modes which can propagate in a pipe: longitudinal, torsional and flexural modes. Even if many authors have investigated the guided waves in pipes, in the present research we are focusing on generating a high energy ultrasonic pulse, capable to produce detectable signals from small defects. Moreover we discuss the probability of detectability of defects near and especially on pipe bends. Using our in-house specialized software package to determine the dispersion curves and displacements fields, we determine the incident modes sent in a pipe from its free end, as in heat exchangers. These results are used for optimal numerical simulation, using the Finite Elements Method (FEM), in order to determine the defect detectability. The numerical data are compared with results obtained in laboratory experiments standard equipment for ultrasonic NDT.
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The aim of this paper is to present an algorithm for computing the fractional Fourier transform integrated into the pipeline of processing multi-variate and distributed data recorded by the engine control unit (ECU) of a car and its... more
The aim of this paper is to present an algorithm for computing the fractional Fourier transform integrated into the pipeline of processing multi-variate and distributed data recorded by the engine control unit (ECU) of a car and its satellites. The role of this transform is vital in establishing a time-variant filter and therefore it must be computed in a fast way. But for large scale time series, the application of the discrete fractional Fourier transform involves the computations of a large number of Hermite polynomials of increasingly order. The parallel algorithm presented will optimally compute the discrete Fourier-type transform for any given angle.
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The paper describes the pressure-wave propagation in a muffler for an internal combustion engine in case of two combined mufflers geometry. The approach is generally applicable to analyzing the damping of propagation of harmonic pressure... more
The paper describes the pressure-wave propagation in a muffler for an internal combustion engine in case of two combined mufflers geometry. The approach is generally applicable to analyzing the damping of propagation of harmonic pressure waves. The paper purpose is to show finite elements analysis of both inductive and resistive damping in pressure acoustics. The main output is the attenuation and acoustic pressure levels for the frequency range 50 Hz-3000 Hz.
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This paper, as part of a series dedicated to highlight the way how natural frequencies of plates change due to damage, presents results of numerical and experimental modal analysis made on thin rectangular plates clamped at all four... more
This paper, as part of a series dedicated to highlight the way how natural frequencies of plates change due to damage, presents results of numerical and experimental modal analysis made on thin rectangular plates clamped at all four lateral surfaces. These results where processed and the so-called relative frequency shift for thirty vibration modes determined. It was revealed the rules how the frequencies change by varying the damage geometry, and proved that these data ca be used for damage identification. Finally, the results are compared with measurements, in order to demonstrate the validity of the theoretical considerations.
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Noise is a well known source of environmental pollution in urban areas or at work. Sound pressure level has a harmful effect on human health. In this paper we present our research on making a new type of composite material and testing its... more
Noise is a well known source of environmental pollution in urban areas or at work. Sound pressure level has a harmful effect on human health. In this paper we present our research on making a new type of composite material and testing its properties of noise attenuation level. Tests were carried out in the anechoic chamber using barrier attenuators of sound waves made of composite material consisting of 50% formaldehyde resin reinforced polypropylene granules formed from waste 50%. It was also determined the efficiency of the panel by calculating the diffraction pression according to the sound waves dispersion on the acoustic panel's surface and mapping the attenuation of noise levels due to the composite material.. Zgomotul este o sursă bine cunoscută de poluare a mediului din zonele urbane sau la locul de muncă. Nivelul de presiune sonoră produce efecte nocive asupra sănătăţii oamenilor. În această lucrare sunt prezentate cercetări efectuate privind elaborarea unui nou tip de material compozit precum şi testarea proprietăţilor lui de atenuare a nivelului de zgomot. S-au efectuat teste în camera anecoică utilizându-se un panou acustic din material compozit alcătuit din răşină formaldehidică 50% armată cu deşeu format din granule de polipropilenă 50%. De asemenea, s-a determinat eficienţa panoului prin calcularea presiunii difractate în funcţie de dispersia undelor acustice pe conturul panoului acustic şi evidenţierea atenuării acustice a panoului din material compozit.
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The paper analyzes the possibility of determining the acoustic absorption coefficient by means of mathematical models from the literature for new composite porous materials. The materials studied were made of fir sawdust and flexible... more
The paper analyzes the possibility of determining the acoustic absorption coefficient by means of mathematical models from the literature for new composite porous materials. The materials studied were made of fir sawdust and flexible polyurethane foam with open pores. The acoustic absorption coefficient of the materials was determined experimentally by means of the impedance tube. The experimental results were compared with those obtained by modeling with the Maple 16 software, by inserting the material characteristics into the mathematical equations. The models used in this study were Delanz-Bayley adapted for foams, Allard-Champoux and Hamet-Berengeir. The results of this study show that the analyzed models are not suitable for new composite porous materials and that new models should be developed to correctly describe their acoustic absorption properties.
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Analysis and design of protection systems for buildings, bridges, and industrial structures have witnessed extensive research activities in the last decades. Nowadays, the conventional antiseismic design of structures is not limited to... more
Analysis and design of protection systems for buildings, bridges, and industrial structures have witnessed extensive research activities in the last decades. Nowadays, the conventional antiseismic design of structures is not limited to their strengthening, but it ensures also a dynamic behavior that avoids damage on the structural elements. A special focus is laid on protecting humans and the nonstructural elements, including the building contents. e goal of this special issue is to collect the latest theoretical achievements, highlight innovative applications, and provide surveys about the current state of the art in the domain of seismic protection of structures. We invite scientists and practitioners to contribute high-quality original research articles, which addresses the abovementioned area. Potential topics include, but are not limited to: Recent advances in the design of seismic isolation systems Elastomeric bearings Shock absorbers and shock mounts Removable dissipative elements Modeling the static and dynamic structural response to earthquake Structural monitoring and postseismic integrity evaluation Estimation of seismic risk Vibration testing facilities and procedures Authors can submit their manuscripts via the Manuscript Tracking System at