Gilbert Rainer GILLICH


32-75 METODĂ DE DETECTARE A DEFECTELOR GRINZILOR ÎNCASTRATE LA AMBELE CAPETE SUPUSE VARIAŢIILOR DE TEMPERATURĂ

METHOD TO DETECT STRUCTURAL DAMAGE
IN DOUBLE-CLAMPED BEAMS IN
CHANGING TEMPERATURE ENVIRONMENT
In this paper we present a method to detect damages in beam-like structures applicable if the temperature during structural monitoring is subject of changes. Experiments are performed on a steel beam for the intact case to attain a baseline. Afterwards, measurements are performed on a beam with known damage location. Comparison is made via Minkowski distance, and the location is found with precision, proving that the developed method is applicable for beams if temperature changes are present during monitoring.
Keywords: damage detection, natural frequency, temperature, filtering, correction, experimental method
Cuvinte cheie: detectarea defectelor, frecvenţe proprii, temperatura, filtrare, corectare, metoda experimentală

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32-74 FILTRAREA ŞI CORECTAREA VALORILOR FRECVENŢELOR PROPRII ALE GRINZII DUBLU ÎNCASTRATE EXPUSĂ INFLUENŢEI VARIAŢIILOR DE TEMPERATURĂ

FILTERING AND CORRECTION OF NATURAL
FREQUENCY VALUES FOR A DOUBLE-CLAMPED BEAM
SUBJECTED TO TEMPERATURE CHANGES
This paper presents the effect of temperature changes on the natural frequencies of beams. These may have perfect or elastic restraints at ends. A temperature increase produces compressive stress and consequently a natural frequency decrease. We contrived mathematical relations to evaluate the effect of temperature for the cases of perfect rigid as well as for elastic restraints. If the beam is imperfect, i.e. anisotropic, non-homogeneous or not strength in the initial state, a correction term has to be employed to accurately find the frequencies. The correction method is also presented.
Keywords: natural frequencies, filtering, correction algorithm, temperature
Cuvinte cheie: frecvenţe proprii, filtrare, metodă de corecţie, temperatura

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32-59 EFICIENŢA DIFERIŢILOR ESTIMATORI AI DISIMILARITĂŢII UTILIZAŢI ÎN DETECTAREA DEFECTELOR

THE EFFICIENCY OF SEVERAL DISSIMILARITY ESTIMATORS USED IN DAMAGE DETECTION

 

This paper deals with damage detection methods based on interpreting the results of vibration measurement. We briefly described an own method for damage evaluation, which takes into account a large number of frequencies achieved from weak axis bending modes. This allows the precise location of the defect location. We represented two histogram types, one with measurements and several resulted from calculations for possible damage scenarios. The damage location was determined with three estimators, among those the best results being attained with the Minkowski distance.

 

Keywords: damage, severity assessment, natural frequencies, vibration

Cuvinte cheie: defecte, evaluarea severității, frecvenţe naturale, vibraţii

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32-58 MODIFICAREA DISTRIBUŢIEI TENSIUNILOR ÎN ZONA DEFECTULUI ŞI EFECTUL ACESTEIA ASUPRA FRECVENŢELOR PROPRII ALE GRINZII

STRESS DISTRIBUTION ALTERATION IN THE DAMAGED ZONE AND ITS EFFECT ON THE BEAM’S NATURAL FREQUENCIES

 

In this paper the relation to be used for deriving the frequency of a beam with transverse crack is tested against finite elements method (FEM) simulation results. We have first analytically derived the beam deflection and compared with results achieved by means of the FEM simulation. The good concordance was found, thus the FEM model is calibrated. Afterwards, damage of different depth was introduced in the beam and the natural frequencies derived. These values were compared against results attained by applying the proposed relation and a good fit was found.

 

Keywords: beam, damage detection, vibration, natural frequencies, deflection

Cuvinte cheie: grindă, detectarea defectelor, vibraţii, frecvenţe proprii, săgeată

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32-57 DESPRE MODIFICAREA FRECVENŢELOR NATURALE ALE GRINZILOR DATORITĂ COROZIUNII

ON THE NATURAL FREQUENCY CHANGES OF

BEAMS DUE TO CORROSION

 

This paper presents a relation to be used for deriving the effect of mass loss on the natural frequencies of beams. Herein the stiffness decrease is not considered, since its effect on the natural frequencies is well-known. Consequently, the beam was considered with a constant cross-section but with reduced volumetric mass density in the corroded region. By this approach, we have first analytically studied the beam dynamics from an energetic point of view and contrived the mathematical relation. Afterwards, this relation was successfully tested against FEM simulations.

 

Keywords: beam, corrosion, vibration, natural frequencies, mode shape

Cuvinte cheie: grindă, coroziune, vibraţii, frecvenţe naturale, formă modală

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29-86 METODE DE EVIDENŢIERE A FRECVENŢELOR APROPIATE

METHODS TO HIGHLIGTH CLOSE FREQUENCY
This paper offers an overview of simpler methods to accurately
estimate frequencies. In standard signal processing, the precision of frequency
estimation increases once the frequency resolution is improved. A finer
resolution is achieved by increasing the observation time interval. If this cannot
be done, the signal length can be artificially extended through the so-called
”zero-padding” method, by adding a number of samples with null amplitude.
The methods have been tested for concrete cases, using the signal processing
tool offered by the open source software, Scilab.
Keywords: signal processing, spectral analyze, “zero-padding” method,
Scilab environment
Cuvinte cheie: procesarea semnalelor, analiza spectrală, metoda
“zero-padding”, mediul Scilab

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29-82 STUDIUL CIOCNIRII ROLELOR DE RULMENT RADIAL PRIN METODE NUMERICE DE CALCUL

BALL BEARINGS RADIAL COLLISION STUDY
BY NUMERICAL CALCULATION
The paper shows that the wheels now fitted radial bearings collide
during the manufacturing process. As a result of this rolls surface defects occur
due to collision elastic-plastic material. For different cases of collision was
made a study on the state of stresses and strains using the Finite Element
Method.
Keywords: radial roller bearing, Elastoplast’s clash, finite element
method
Cuvinte cheie: rulment radial cu role, ciocnire elasto-plastică, metoda
elementelor finite

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29-77 INFLUENŢA DEFECTULUI ASUPRA MODIFICĂRII TEMPERATURII CRITICE LA FLAMB

DAMAGE INFLUENCE ON THE CRITICAL BUCKLING
TEMPERATURE
This paper presents the influence of a transverse damage in a doubleclamped
beam upon the critical buckling temperature. First, the buckling
temperatures and subsequent loads are analytically investigated on an intact
prismatic beam, together with the dynamic behavior in terms of the natural
frequencies. Afterwards, the effect of a transverse damage is considered, and a
relation expressing the frequency alteration due to the crack is provided. To
prove the relation’s validity a finite element analysis was performed for some
particular cases, and the results compared with those obtained analytically. The
investigation did show a good concordance between the results obtained in the
two ways, proving the correctness of the analytical approach.
Keywords: double-clamped beam, damage, thermal buckling
Cuvinte cheie: grindă dublu încastrată, defect, flambaj, temperatură
critică

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27-83 INFLUENŢA EFECTULUI TERMIC ASUPRA FRECVENŢELOR PROPRII ALE GRINZILOR ÎNCASTRATE LA AMBELE CAPETE

THE EFFECT OF THERMAL LOAND ON THE NATURAL FREQUENCIES OF DOUBLE-CLAMPED BEAMS
The natural frequencies of double-clamped beams are influenced by environmental conditions and operational loads. For instance the temperature induces axial loads due to restraint displacements, which lead after a critical temperature increase to buckling. This paper clarifies the effect of external loads on the natural frequencies of beams.
Keywords: thermal loads, buckling, Euler-Bernoulli beam, natural frequency
Cuvinte cheie: încărcări termice, flambaj, grindă, frecvenţe proprii

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26-75 CONSIDERAŢII PRIVIND CALCULUL DE REZISTENȚĂ AL TRANSMISIILOR PLANETARE

CONSIDERATIONS ON THE RESISTANCE CALCULATION OF PLANETARY TRANSMISSIONS
At the design of the gears from a planetary transmission, there appear some differences compared to the cylindrical or helical gears. Furthermore the crown gear is of particular importance in the calculation of these transmissions. A reduction in the thickness of the crown gear, in order to ensure certain elasticity, leads to a reduction of the total mass and to a better distribution of the load in a planetary transmission, but with the disadvantage that the load increases in the foot of the gear crown. Therefore, the calculation of the crown gear resistance increased in complexity and importance.

Keywords: Planetary transmission, voltages, calculation of resistance

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26-38 INFLUENŢA TEMPERATURII ASUPRA FRECVENŢELOR PROPRII ALE ELEMENTELOR DIN STRUCTURI CU ZĂBRELE

TEMPERATURE EFFECT UPON THE NATURAL FREQUENCIES OF THRUSS ELEMENTS
In this paper we analyze the effect of temperature upon the natural frequencies of truss elements. Temperature changes influence the Young’s modulus in the sense that it decreases with increasing temperature, consequently structural elements frequencies decrease. However, we demonstrate in this paper that the frequency changes due to temperature in natural environment are very small and do not dramatically influence the structures dynamic behavior.
Keywords: temperature, Young modulus, frequency, truss structures

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26-35 TRANSMISIBILITATEA VIBRAŢIILOR PROVOCATE DE SISTEMELE DE ACŢIONARE ŞI IZOLAREA ACESTORA

VIBRATION TRANSMISSIBILITY CAUSED BY DRIVE
SYSTEMS AND THEIR ISOLATION
The paper present capability of different materials to diminish the
transmissibility of vibrations caused by diverse machineries, in order to
increases the operational safety, protect the operators against dangerous
vibration effects and improve the equipment’s performances.
Keywords: transmissibility, sponge, polystyrene, rubber
Cuvinte cheie: transmisibilitate, burete, polistiren, cauciuc
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25-66 STUDIUL COMPORTĂRII STRUCTURILOR IZOLATE CU SISTEME PENDULARE

STUDY OF THE BEHAVIOUR OF STRUCTURES
INSULATED WITH FRICTION PENDULUM SYSTEMS – II
The earthquakes have been, and are a great danger against humanity.
The study presented in this paper aims to determine the response of an
insulated structure due to earthquakes vibration loads, which are randomly,
non-periodic and contain various frequencies. The study, made on a two-story
structure involved finite element analysis, to determine the displacements,
velocities and accelerations in various locations on the structure. The actual
results were obtained using statistical methods, in order to determine the
dynamic behaviour of a vibrating structure.
Keywords: base isolation, friction, pendulum, structure
Cuvinte cheie: izolator seismic, frecare, pendul, structură
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25-65 STUDIUL COMPORTĂRII STRUCTURILOR IZOLATE CU SISTEME PENDULARE CU FRECARE Partea I-a

STUDY OF THE BEHAVIOUR OF STRUCTURES INSULATED
WITH FRICTION PENDULUM SYSTEMS – I
The earthquakes have been, and are a great danger against humanity.
The study presented in this paper aims to determine the response of an
insulated structure due to earthquakes vibration loads, which are randomly,
non-periodic and contain various frequencies. The study, made on a two-story
structure involved finite element analysis, to determine the displacements,
velocities and accelerations in various locations on the structure. The actual
results were obtained using statistical methods, in order to determine the
dynamic behavior of a vibrating structure.
Keywords: base isolation, friction, pendulum, structure
Cuvinte cheie: izolator seismic, frecare, pendul, structură
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25-64 STUDIUL COMPORTĂRII DINAMICE A STÂLPILOR CU DIFERITE NIVELE DE ÎNCĂRCARE

A STUDY REGARDING THE DYNAMIC BEHAVIOR OF
COLUMNS SUBJECTED TO DIFFERENT TIP MASSES
The present study aims to highlight the effect of a tip mass upon the
behavior of columns. We have first analytically determined, for a specific
column, the critical buckling force to find the range in which it works in the
elastic domain. Afterwards, by means of numerical simulations, we performed
analysis regarding the influence of loads due to different additional masses and
have identified the effect upon the natural frequencies and modal shapes,
concluding that the higher the mode number, the higher the influence.
Keywords: column, buckling, natural frequency, simulation
Cuvinte cheie: stâlp, flambaj, frecvenţe proprii, simulare
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25-63 EFECTUL DEFECTELOR STRUCTURALE ASUPRA COMPORTAMENTULUI DINAMIC AL GRINZILOR COMPOZITE STRATIFICATE

EFFECT OF STRUCTURAL DAMAGES ON THE DYNAMIC
BEHAVIOUR OF LAMINATED BEAMS
This paper presents results obtained by modal analysis on composite
beam-like structures in healthy and damaged state. The aim is to obtain
damage “signatures” for all possible damage scenarios and to use these data
to assess transversal cracks based on vibration techniques, by involving natural
frequency shifts. The analysis was performed in SolidWorks software for a fivelayer
composite, 30 vibration modes being obtained by numerical simulations.
An example how to interpret the results is shown in the last section of the
paper.
Keywords: damage, finite elements, frequency, simulation, structure
Cuvinte cheie: defect, elemente finite, frecvenţă, simulare, structură
Descarcare text


19-90 DETERMINAREA GRAFO-ANALITICĂ PE BAZA FRECVENŢEI PROPRII A ADÂNCIMII DEFECTULUI LA BARE ÎNCASTRATE

GRAPHIC-ANALYTICAL METHOD FOR DAMAGE DEPTH
DETERMINATION BASED ON NATURAL FREQUENCIES
AT CANTILEVER BEAM
The paper presents research results of authors in determining of the
damage depth for a cantilever beams by using natural frequencies. A graphicanalytical
method is proposed which permit to evaluate the damage depth and
localize the position of the damage on the beam length. The method is based
on results obtained from the numerical modal analysis for the first ten modes of
vibration. Experimental tests have confirmed the method and the results have
application in non-destructive examination based on vibration analysis.
Keywords: natural frequencies, defect, depth, bar mixer
Cuvinte cheie: frecvenţe proprii, defect, adâncime, bară încastrată

90 DETERMINAREA GRAFO-ANALITICĂ PE BAZA


19-97 LOCALIZAREA DEFECTULUI ÎN BARE ÎNCASTRATE UTILIZÂND INDICELE ABATERII RELATIVE A FRECVENŢELOR PROPRII

LOCALIZATION OF DAMAGE IN CANTILEVER BEAMS USING
THE RELATIVE SHIFT IN NATURAL FREQUENCIES
This paper presents a method to locate the damages in cantilever
beams based on relative shift in natural frequencies. This method takes in to
account the particular manner in which the natural frequencies of the first then
modes change due to the occurrence of damage. The measured frequencies
changes are a compared with values contained in a databases, determined on
models using the finite element method. For these databases we consider a
large number of damages locations. By comparing the changes in frequencies
obtained trough measurements with those determined on models, for the first
ten vibration modes, it was possible to locate damages with high accuracy.
Keywords: vibration, bar mixer, frequencies, detecting defects
Cuvinte cheie: vibraţii, bară încastrată, frecvenţe proprii, detectarea
defectelor

97 LOCALIZAREA DEFECTULUI ÎN BARE ÎNCASTRATE


23-62 DETERMINAREA FRECVENŢELOR PROPRII ALE BARELOR COTITE

DETERMINING THE NATURAL FREQUENCIES
OF BENDED BEAMS
This paper presents the natural frequencies obtained from modal
analysis, performed with ANSYS software, for the first 60 vibration modes of a
bended bar (L shape) without defect and with defects situated on three different
locations along the column. The research was made in order to highlight the
changes of the structure’s dynamic behaviour in terms of natural frequencies.
Cuvinte cheie: frecvenţe proprii, bara cotită, detectarea defectelor, simulare
Keywords: natural frequencies, bended beam, damage detection, simulation

23-62 DETERMINAREA FRECVENŢELOR PROPRII

 


23-65 ANALIZA DISPOZITIVELOR DE IZOLARE SEISMICĂ DIN ELASTOMERI FĂRĂ ŞI CU INIMĂ DE PLUMB

ANALYSIS OF ELASTOMERIC INSULATORS
WITHOUT AND WITH LEAD HEART
Seismic isolation using neopren rubber bearings or lead rubber bearings
is achieved by inserting these devices between the infrastructure and the
superstructure in order to retrieve and dissipate seismic energy so that the
constructions will not by damage.
These devices are designed and built according to the size, complexity,
degree of loading and seismic zone where the construction will be located.
Cuvinte cheie: izolator, elastomer, inimă de plumb, rigiditate
Keywords: insulator, elastomer, lead heart, stiffness

23-65 ANALIZA DISPOZITIVELOR DE IZOLARE SEISMICĂ


23-74 CONSIDERAŢII PRIVIND OPORTUNITATEA UTILIZĂRII MODELULUI SHEAR PENTRU BARE DE DIFERITE LUNGIMI

CONSIDERATIONS THE USE OF SHEAR MODEL FOR
BEAMS OF DIFFERENT LENGTHS
This paper presents a study of dynamic behaviour for different lenghts of
beams, preserving constat section. The natural frequencies on beams, for 8
bending vibration modes after weak axis were determinated using Sh model
and by FEM analysis. For any lenght of beam, the result is pretty good,
acceptable errors.
Cuvinte cheie: vibraţii, modul formei de vibraţie, frecvenţe, metoda Shear
Keywords: vibrations, mode shape, frequencies, the Shear method

23-74 CONSIDERAŢII PRIVIND OPORTUNITATEA


23-75 CONSIDERAŢII PRIVIND OPORTUNITATEA UTILIZĂRII MODELULUI EULER-BERNOULLI PENTRU BARE DE DIFERITE LUNGIMI

CONSIDERATIONS THE USE OF EULER-BERNOULLI
MODEL FOR BEAMS OF DIFFERENT LENGTHS
This paper presents a study of dynamic behaviour for different lengths of
beams, preserving constant section. The natural frequencies on beams, for 8
bending vibration modes after weak axis were determinates using EB model
and by FEM analysis. The comparative study showed that for long lengths, the
model is sufficiently precise, while the lengths of the beams the errors are
significant. The comparative study showed that for long beams the model is
very precise, while the shorter lengths the errors are significant.
Cuvinte cheie: vibraţii, modul formei de vibraţie, frecvenţe, metoda
Euler-Bernoulli
Keywords: vibrations, mode shape, frequencies, the Euler-Bernoulli
method

23-75 CONSIDERAŢII PRIVIND OPORTUNITATEA UTILIZĂRII MODELULUI EULER-BERNOULLI PENTRU


23-76 CONSIDERAŢII PRIVIND EFECTELE COROZIUNII ASUPRA COMPORTAMENTULUI DINAMIC AL GRINZILOR

CONSIDERATIONS REGARDING CORROSION EFFECTS
ON BEAMS DYNAMIC BEHAVIOR
Negative effects caused by corrosion are significant, both economically
and in terms of public safety, so incipient detection of corroded areas is
necessary to take in real-time measures to prevent the occurrence of
dangerous situations. This paper presents types of corrosion and various actual
methods used to detect corroded areas together with a new approach in
damage detection based on vibration measurements. While the proposed
method base on frequency changes, to understand the dynamic behaviour of
beams subjected to corrosion is a first step. It permits establishing appropriate
mathematical models and development of damage detection methods implying
the monitoring and analyzes of beams natural frequencies.
Cuvinte cheie: coroziune, detectarea defectelor, frecvenţe proprii
Keywords: corrosion, damage detection, natural frequency

23-76 CONSIDERAŢII PRIVIND EFECTELE COROZIUNII


21-84 EFECTUL DEFECTULUI ASUPRA COMPORTĂRII DINAMICE A GRINZILOR

THE DAMAGE EFFECT ON DYNAMIC BEHAVIOUR OF
BEAMS
Structural Health Monitoring (SHM) for civil engineering applications
involves the use of sensing networks in order to diagnose damage in large
scale civil structures such as buildings, bridges, aircraft. SHM will result in large
savings in maintenance costs as well as improving life safety by providing a
real-time updating of a structure’s integrity.
Cuvinte cheie: defect, vibraţii, senzori, bară încastrată
Keywords: failure, vibration sensors, embedded bar

84 EFECTUL DEFECTULUI ASUPRA COMPORTĂRII DINAMICE A GRINZILOR


22-61 STADIUL ACTUAL PRIVIND DETECTAREA VIBROACUSTICĂ A DEFECTELOR ÎN BARE PRISMATICE – Partea a II-a

The paper contains a review of the technical literature concerning the
detection, location, and characterization of structural damage via techniques
that examine changes in measured structural vibration response. The report
first categorizes the methods according to required measured data and analysis
technique. The report describes the development of the damage-identification
methods and summarizes the current state-of-the-art of the technology.
Cuvinte cheie: vibraţii, detectarea vibroacustică a defectelor, bare
prismatice
Keywords: vibration, vibration detection of defects, prismatic bars

61 STADIUL ACTUAL PRIVIND DETECTAREA


22-60 STADIUL ACTUAL PRIVIND DETECTAREA VIBROACUSTICĂ A DEFECTELOR ÎN BARE PRISMATICE – Partea I

The paper contains a review of the technical literature concerning the
detection, location, and characterization of structural damage via techniques
that examine changes in measured structural vibration response. The report
first categorizes the methods according to required measured data and analysis
technique. The report describes the development of the damage-identification
methods and summarizes the current state-of-the-art of the technology.
Cuvinte cheie: vibraţii, detectarea vibroacustică a defectelor, bare
prismatice Keywords: vibration, vibration detection of defects, prismatic bars

60 STADIUL ACTUAL PRIVIND DETECTAREA


22-20 ANALIZA FEM A SISTEMELOR DE IZOLARE SEISMICĂ CU SUPRAFAŢA DE ALUNECARE GENERATĂ DE FUNCŢII POLINOMIALE

Earthquake isolation systems are devices located at the base of
overhead structures (civil works), which have the goal to take off the oscillating
period of this compared with ground, during an earthquake and decrease the
transmitted energy using frictional dissipation. The results of the study
presented of this paper relieve the possibility of using sliding surfaces
generated by polynomial functions by using an intermediate neoprene element
between the sliding surface and the slider.
Cuvinte cheie: izolator seismic, pendul cu fricţiune, neopren, funcție
polinomială, analiză FEM
Keywords: seismic isolation, friction pendulum, neoprene, polynomial
function, FEM analysis

20 ANALIZA FEM A SISTEMELOR DE IZOLARE SEISMICĂ


22-19 SISTEME INOVATIVE DE IZOLARE SEISMICĂ BAZATE PE DISIPAREA ENERGIEI PRIN FRECARE. ANALIZA STATICĂ

Friction pendulums are used to reduce forces transmitted from the
ground to buildings, in order to diminish or avoid earthquakes loss, by
permitting relative displacements between the isolated structure and earth
during seismic actions. The result consists in reduced accelerations and
consequently reduced inertia forces. In this paper we present a new approach
regarding implementation of a friction pendulum having the sliding surface
profile based on a polynomial function of superior order. The new device
implies the use of an elastic element between the slider and the sliding surface.
Static and dynamic analyses performed using the finite element method
confirmed that the use of an elastomeric element is suitable for this purpose.
Cuvinte cheie: pendul cu fricţiune, suprafaţa de alunecare, funcţii
polinomiale, element elastomeric
Keywords: friction pendulum, sliding surface, polynomial functions,
elastomeric element

19 SISTEME INOVATIVE DE IZOLARE SEISMICĂ


22-18 ANALIZA IZOLATORILOR ELASTOMERICI UTILIZÂND METODA ELEMENTELOR FINITE

Modern design methods require in certain phases the use of finite
element analysis, which allows development of safe projects in terms of
structural strength and durability. Using this analysis in the design process
provides the following advantages: cost reduction and production design,
material economy, recognizing weaknesses, quality design and construction
optimization. The paper presents an innovative base isolation device based
with increased number of adjustable parameters, for which good simulation
results were obtained.
Cuvinte cheie: analiză, element finit, izolarea bazei, elastomer
Keywords: analysis, finite element, base isolation, elastomeric

18 ANALIZA IZOLATORILOR ELASTOMERICI


22-17 SISTEME INOVATIVE DE IZOLARE SEISMICĂ BAZATE PE DISIPAREA ENERGIEI PRIN FRECARE. MODEL ANALITIC

In this paper we present an innovative system for seismic isolation
based on frictional energy dissipation. While classical friction pendulum
bearings contain one or more cylindrical or spherical sliding surfaces, they
provide just pairs of two parameters controlling the dynamic behavior of a
structure isolated by this kind of device. In this paper we are implementing
friction pendulums having the sliding surface profile based on a polynomial
function of superior order. This seismic isolation system permit a greater
flexibility in controlling the oscillations of the upper structure, in terms of
displacements or dissipated energy, by using three parameters to control the
force-displacement relation.
Cuvinte cheie: pendul cu fricţiune, suprafaţa de alunecare, funcţii
polinomiale, energia disipată
Keywords: friction pendulum, sliding surface, polynomial functions,
disipated energy

17 SISTEME INOVATIVE DE IZOLARE SEISMICĂ BAZATE