Mass-Spring Systems

1 Structure-Borne Noise and
Its Consequences

Calm sets inRoad traffic and trains cause structure-borne noise due to their speed
and weight. This noise spreads out
through the ground and causes
vibrations in buildings and nearby
machines or sensitive measurement
equipment.

uildings, equipment and machines
are themselves systems capable ofvibration. Excitation by trains or traffic
is amplified by the structure of thebuildings and objects affected. The
mechanical vibrations and the resulting
secondary air-borne sound, in otherwords noise, are harmful to humans in
the case of long-term exposure.

B

Vibrations also influence the functioning of machines and equipment, insome cases significantly impairing theiroperation or negatively influencing
quality and productivity. In addition,
dynamic overloading of the building
structure poses the risk of damage tothe building, such as subsiding andcracks.

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2 Highly Effective
Structure-Borne Noise Protection

Effective
over decades

4

tructure-borne sound emissions
can be reduced at their point oforigin through various measures
tailored to the specific requirements.
Mass-spring systems are used insituations where the highest demands
are placed on structure-borne soundprotection. The materials Sylomer® andS

Sylodyn® are used throughout theworld as individual, elastic supports.
They guarantee the required effectiveness for decades. Combined with
Getzner’s technical know-how, theseproven materials are now considered
to be the standard high-tech solution
for mass-spring systems.

Advantages ofSylomer ® and Sylodyn ® supports

Sylomer® and Sylodyn® are the ideal
materials for use as highly elastic
supports in a mass-spring system –whatever the construction method.

— Reliable, homogenous and lasting elasticity— Short-term, even extreme, overloading is possible— Can be directly driven over by heavy vehicles— Low construction costs thanks to simple and fast installation— Various shapes are possible by varying the density, thickness
and loaded area of the material— High efficiency and long-term stability— Minimal maintenance expenses5

3 How a Mass-Spring System
Functions

Effectively isolating
vibrations
The goal of vibration isolation is to
dynamically decouple the superstructure from its environment in order toreduce the transmission of vibrations
and structure-borne sound.

Fe(t)his decoupling is achieved by creating a system capable of vibration. If
a permanently elastic spring layer, suchas Sylomer® or Sylodyn®, is installed,
the isolation takes place directly at thesource of the emissions. This ensuresthat the support point force Fu(t) issmaller than the exciter force Fe(t), resulting in reduced vibrations producedby the support point forces.

T

m

c

d

Fu(t)

he function of an elasticallysupported superstructure can be
described very easily using an alternate system, referred to as a single
degree of freedom system. Many
vibration problems can be approximately explained with this simple
physical model. If the superstructure
mass is brought out of equilibrium bya brief exciter force Fe(t), the mass
executes vibrations with the natural
frequency f0.

T6

c = dynamic spring stiffness
m = superstructure mass +unsprung mass of wheelset

he speed with which these vibrations decrease in amplitude depends on the damping of the spring.
For Sylomer® and Sylodyn® materials,
the damping is described by themechanical loss factor.

Two areas exist in the vibration
isolation system, namely an
amplification area and an isolation
area.

T

Load transmission factor VR

The amplitude frequency response(amount of transmission function) must
be determined in order to evaluate a
mass-spring system. This describes theamplitude relationship based on thefrequency f or based on the frequency
relationship between the support point
force Fu(t) and the exciter force Fe(t) inthe case of source isolation.

3.0
0.2
0

The amplification only occurs if an
exciter frequency is present thatmatches the natural frequency of theelastic support or in the case ofbroadband stimulation.
The isolation starts at a frequency that
corresponds to 2•f0. The amplitude
frequency response indicates that theamplification at the insulator natural
frequency f0 is reduced with an increas-

0.1
0

2.5

0.3

2.0

ing level of damping, while the level ofisolation decreases with increasing
damping.
In terms of the properties of the spring
in a mass-spring system, this meansthat the system must have the lowest
possible ratio of dynamic to static
stiffness. The dynamic stiffness of the
support should also only be subject tominor changes due to frequency andload.
The dimensioning of a mass-spring
system is an optimization problem forengineers. This problem requires
in-depth and specialized knowledge,
which Getzner has offered with its
partners for years. The functioning of amass-spring system can, however, begreatly affected by standing water
under the mass trough and within thesystem. When installing a mass-spring
system, it is therefore essential toensure sufficient long-term drainage.

0.5

1.5

0.8
1.0

=1.0

0.8

0.3
0.2

0.5

0.5
0.1
Amplification
Isolation

0.0
0.3 0.4

0.6

0.8

1

2

2

3

4
5 6 7 8Tuning ratio

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4 Design
Variants

A number of different designs havebeen developed by European railway
companies for mass-spring systems inrecent decades. For instance, there
are designs with either in-situ casted
or prefabricated concrete slabs aswell as combinations of the two, bothwith and without ballast beds.
n designing an elastic support for
mass-spring systems, the selected
construction method is also important
for the functionality and economic
efficiency of the overall system.

I

Whether full-surface, linear or pointlike support – Getzner’s know-how
ensures technically faultless, economically sustainable and functional
solutions.

8Full-surface support

Linear support

Point-like support

Full-surface
supportLinearsupportPoint-like
supportepending on the specific application, a full-surface elastic support
achieves natural frequencies in therange of 14-25 Hz. This corresponds toan achievable structure-borne noise
damping of up to 30 dB in the supercritical frequency range.

inear supports are preferred in
mass-spring systems that make useof prefabricated elements or combine
prefab with in-situ casted concrete. The
horizontal forces that arise both in the
direction of travel (braking and acceleration forces) as well as perpendicular
to the track axis (e.g. centrifugal forces,
side forces resulting from track geometry errors) can be handled well by the
relatively large support surfaces.

TD

A full-surface elastic support fromGetzner offers advantages in thefollowing areas:— Simple, fast and inexpensive construction methods— Low risk of construction errors— Wide-area load distribution in thesubsoil— Damping of structural vibrations of
the track support elements— Low number of installation joints— High horizontal stability of the entire
system— Economy of the entire system

LWith linear support, it is possible toachieve lower support structure
natural frequencies (8-15 Hz) than withfull-surface support while keeping
expenses reasonable. Overall, linear
support achieves a higher damping ofstructure-borne sound.

he selected construction method
for the track support slabs or track
troughs determines the type ofpoint-like support. Generally it is usedwith track support slabs created usingsite-mixed concrete and lifted into
place after hardening. The supports
are inserted through openings in theplate.
Since train operations give rise tohorizontal forces, attention must be
paid to the transmission of these forces
during dimensioning of the generally
relatively small support surfaces. In
order to limit the horizontal deflections
in line with the requirements, theoptimal values for shear modulus,
support layer thickness and support
area are used in practice.
The lowest natural frequencies areachievable with point-like supports(5-12 Hz). This type of support satisfies the highest requirements forstructure-borne sound protection.
Structure-borne sound damping of
30 dB and more can be achieved withthis type of system.

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5 Design of ElasticallySupported Transitions

For a smoothtransition
he transition areas between
neighboring superstructure types(ballasted track, slab track) must beplanned very precisely in order toprevent lasting flaws in the track.
Transition areas always arise for massspring systems since these are accompanied by higher deflection thannormal superstructures. Due to temperature fluctuations and concrete
deterioration, the transition areas arealso subject to special loads. Getzner
offers competent solutions in this area
as well.

T

For example, the required system
stiffness in the transition structures
can be achieved in the following ways:(FEA), Getzner calculates and simulates
all factors for the optimal design oftransition areas.

— Compressed support arrangement— Change to the support material
stiffness— Installation of special rail fastenings— Installation of undersleeper pads
The fact that excessive support point
forces can overload a rail fastening
must be considered during implementation. Using finite element analysis

Transition between
mass-spring system andslab track with elastic
undersleeper pads.
Ballasted track

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Slab track11

6 Construction
ErrorsOur experiencegives you security
onstruction or design errors andimproper or absent features can insome cases affect the real propertiesof mass-spring systems.

C

Examples include:— Insufficient or absent drainage resulting in a “stamp effect”
within the system— For full-surface systems: absent, unsuitable or excessively stiffside mats— Faulty isolation of cable shafts, drainage inlets and otherconnections— Unsuitable support material or support layer thicknesses below
specific minimums— Large number of installation joints— Improper, careless installation of the support material— Structural design, such as the length of the deck slab or designof the reinforcement, insufficient load distribution on theelastomer

xecution flaws in a mass-spring
system can generally only becorrected later at great expense andeffort. Depending on the severity of theflaws, it is sometimes necessary tocompletely rebuild the track.

E

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7 Requirements for an
Elastomer Support

Multi-facetedand provenor more than four decades, thematerials Sylomer® and Sylodyn®
have proven themselves to be aneffective protection against vibrations
and structure-borne sound in railway
superstructures.

F

Getzner materials contribute to theprotection of structures, improve thestability of railway tracks and reducethe dynamic load on the ballast,
thereby lowering maintenance expenses as well. Even after more than 30
years, railway applications made ofSylomer® and Sylodyn® remain effective. When samples were removed andtested, the elastomer showed nofatigue even after many years of operation.

Conditions for functioning and long-lasting massspring systems:

Especially with partial surface support,
it is particularly important to define
the requirements for the support
material and the quality monitoring on
a project-specific basis.

— Further tests determine the extent to which the track geometry
changes due to creeping, operating loads and environmental
influences.

— The static and dynamic stiffnesses must be evaluated in order todetermine the specifically required properties of the support.
— Changes to the specific support properties due to operating loads
are tested with long-term vibration tests consisting of at least three
million load changes.
— Changes to the support properties due to environmental influences(e.g. ozone, water, oils, chemicals) must also be evaluated.

— The quality of the support is carefully monitored even before
installation.

he standard DIN 45673-7, Mechanical vibration – Resilient elements
used in railway tracks – Part 7: Laboratory test procedures for resilient
elements of mass-spring-systems,
provides additional information on
suitability for use and testing of thestatic-dynamic stiffnesses.

T13

8 Finite Element
Analysis

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Finite element analysis yields
the following results:

Know what you aredealing with— Support capacity of the support slab
— Static deformation due to deadweightsubstitute physical system consisting of mass relationships, stiffnesses and damping coefficients must always
be developed for a system analysis. The most well-known
system analysis method is finite element analysis (FEA).

A— Natural modes— Natural frequencies— Strength information— Dynamic loading and vibration
movements

In vibration isolation, it is generally assumed that the vibration-isolated object (the support slab of the track) and thesubsoil are each rigid bodies. The purpose of this assumption
is to verify the effect of the vibration isolation by way ofsimulation. However, if one wishes to identify limitations andunderstand the total behavior of the system, additional
degrees of freedom that are relevant to the real system are
identified and analyzed using FEA.

— System behavior under defined
stimulation— Prediction of the dynamic behaviorof a system for various systemparameters

he design requirements are constantly growing. Getzner
offers a wide range of services as a competent partner toplanners and engineers working on this complex subject.

T— Required modifications for a desired
dynamic behavior

159 Installation
Information

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Isolation of a mass-spring systemagainst drains

Preparatory
measures

Delivery

Layinghen installing, it is important toensure that the Sylomer® or
Sylodyn® support layer completely
decouples the subsequently laidsupport slab from the environment.
Sound bridges can prevent functional
vibration isolation. It is also important
to ensure drainage of the system.

etzner delivers the materials
directly to the construction site:side mats, linear supports and discrete
supports on pallets, ground mats asrolled sheets with a standard width of
1.50 m. Depending on the geometry
and installation conditions, Getzner
assembles the mats at the factory,
allowing fast and economical installation on-site.

etzner always pays attention to
the total weight when assembling
the rolls. This means that the mats caneasily be laid by a two-man team. In
this way, it is possible to lay over
500 m2 per person each day. Linear
and discrete supports can even be
positioned by a single person. The mat
length or protruding corners can beeasily corrected by the person laying
the mats using disposable knives.

W

The subsoil must therefore be flat andfree of pointed or sharp objects. If thisis only possible to a limited extent, it ispossible, for example, to lay a fleece
between the subsoil and the mat toprotect the support layer. A sub-baseof concrete has also proven effective.
Special discrete bearings must be
stable and accurately positioned. A
corresponding base with a steel frame
represents one effective option.

G

The ground mats can be laid bothparallel and perpendicular to the track
axis. It is important here to keep thenumber of joints to a minimum. The
remaining joints are sealed with tape toprevent the concrete mixture fromentering and creating structure-borne
sound bridges.

G

If desired, Getzner will create professional installation plans or provide aconstruction supervisor to guarantee
proper installation.

Reinforcement may be useful for afull-surface solution. In this case,sufficient load distribution from thereinforcement to the Sylomer® or
Sylodyn® mats must be ensured.
Corresponding supporting surfaces(wood or plastic panels) prevent
excessive surface compression or
deflections.

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10 International
References

etzner solutions can be foundaround the world – as can Getzner
experts. With our 10 branch ofices, wehave a local presence in important geographic regions. We serve practically allof the relevant markets in the world
with our numerous sales partners.

G

Branches in:— Bürs, Austria— Berlin, Germany— Munich, Germany— Stuttgart, Germany— Lyon, France— Amman, Jordan— Tokyo, Japan— Pune, India— Beijing, China— Charlotte, USA

Getzner branch offices
Getzner sales partners
Reference countries

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Milan tram line

Nottingham tram line

rojects realized by Getzner
speak for themselves. Here isa sampling of our reference list in
the railway sector:

Standard-gauge railway

Tram lines

Select projects:— Brenner rail axis,
northern approach line
Brenner Zulauf Nord,
Römerberg Tunnel,
Zammer Tunnel,
Arlberg Tunnel,
New Lainz Tunnel,
Sittenberg Tunnel (ÖBB)— Leipzig City Tunnel
Old Mainz Tunnel
New Mainz Tunnel
City Tunnel Leipzig,
Alter Mainzer Tunnel,
Neuer Mainzer Tunnel,
Tiergarten Tunnel,
Berlin North-South,
Lehrter Bahnhof (train station),
Amperbrücke (bridge),
Cologne/Bonn airport connection,
Siegauen Tunnel,
Audi Tunnel Ingolstadt (DB AG)— NEAT: Zurichberg Tunnel,
Zimmerberg Tunnel (SBB)— Rome-Fiumicino,
Udine-Tarvisio,
Milan-Saronno,
Catania (FS)— Channel Tunnel Rail Link
(Network Rail)— Brussels (SNCB)— Augsburg— Barcelona— Berlin— Bern— Bordeaux— Brest— Constantine— Essen— Florence— Geneva— Gothenburg— Graz— Grenoble— Isfahan— Le Mans— Linz— Lyon— Madrid— Marseille— MashhadP

Munich underground line

— Milan— Montpellier— Munich— Nantes— Nice— Nottingham— Orléans
— Paris - St. Denis— Paris - T1
— Prague— Rome— Rouen— Santo Domingo— Seville— Shiraz— Strasbourg— Stuttgart— Tenerife— Valencia— Vienna

Underground/rapid transit lines— Athens— Augsburg— Berlin— Bochum— Buenos Aires— Dortmund— Düsseldorf— Hong Kong
— Incheon— Krakow— Milan— Munich— New York
— Nuremberg— Sao Paulo— Vienna— Zurich

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Getzner Spring Solutions GmbH
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T +49-7142-91753-0
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info.stuttgart@getzner.com
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FranceT +33-4 72 62 00 16
info.lyon@getzner.com

Getzner Werkstoffe GmbH
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info.tokyo@getzner.com
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www.getzner.com

B MFS Trams en © Copyright by Getzner Werkstoffe GmbH | 07-2016

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