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NOISE & VIBRATIONSSUPPLEMENT

Quality control
measurement of aMSS after 30 yearsof operation
An investigation into the effectiveness of one of the first mass-spring systems (MSS) in Switzerland is currently
ongoing. After 30 years of operation, the vibration-reducing lightweight MSS is still performing without faults,
despite the elastic bearing of the slab now being partially submerged in water. Vibration engineering experts
Adrian Egger and Markus Heim provide further insight.
System descriptionof two longitudinal concrete slabs, each measuring 88cm-wide andThe foundations of sensitive residential buildings lie directly on top

separated by a 44cm-wide longitudinal groove.

of the approximately 2.2km-long tram tunnel in Zurich, which was

The longitudinal slabs are mounted on full-surface elastic Sylomer®

constructed between Milchbuck and Schwamendingen (lines 7 and 9)

mats (Sylomer® LR44) and synthetic sleepers were used as cross

30 years ago.

sleepers, which were mounted on sleeper boots.

To ensure that residents enjoy a high quality of life when theballastless track system with an elastically mounted track slab to protect

Historic and current investigations into
the effectiveness of the vibration measures

the residents from vibrations.

In August 1985, shortly after the commissioning of the track,

tramway line is operating, Verkehrsbetriebe Zürich (VBZ) opted for a

At that time the ‘Viennese system’ served as the template for thesuperstructure in the Schwamendingen tunnel – the difference beingthat polyurethane mats made from Sylomer® should be used as anelastic bearing instead of fibreglass mats.
Commissioned in February 1985 the track superstructure consistsinvestigations into the effectiveness of the vibration measures werecarried out on the track as well as in the adjacent buildings.
After 30 years of operation, new vibration measurements wereenforced in March 2015.
The repetition of the measurements allows us to comment on theS U B S C R I B E O N L I N E A T:

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NOISE & VIBRATIONSSUPPLEMENT
long-term effectiveness of the MSS vibration
measures, which is significantly influenced by
the elastic mats made from Sylomer®.
The vertical vibration velocities weremeasured at nine measuring points in thetunnel during a normal flow of traffic, both in
the area equipped with the MSS and in an
adjacent section of track not equipped with avibration-reducing measure.
Measurements were taken at the same
locations on the tunnel floor next to the tunnel
wall in the MSS section as were used for the1985 survey.
Measurements were also taken at two
additional points located both 12m to the leftand right of the historic measuring point, toobtain greater statistical evidence for thevibrational reduction properties of the MSS.
The track section in the tunnel without MSS
was also monitored in a cross-section.
To verify the continued effectiveness of theprotection measure, the vibrations generated

Graph 1: Insertion loss of the mass-spring system (MSS) for track 700 (without water) andtrack 800 (with water), averaged over all measurement sections with scatterby the trams were recorded – in all three spatial
directions – in the basements of two residential buildings located in theDeteriorating conditions – standing water in the tunnel

immediate vicinity of the tunnel. Once again, the measurement points

The gradients of the track drop slightly in both directions, forming awere identical to those used in 1985.

depression in the middle of the tunnel.

Over 50 sets of measurements were taken with all tram models that

During an on-site inspection water was discovered in thecurrently traverse the network (Be 4/6 Tram 2000, Be 4/6 Tram 2000

longitudinal groove of the lower section track (track 800). The water‘Sänfte’ (including low-floor model) and Be 5/6 Tram 2000 ‘Cobra’).

level was up to 20cm-deep along most of the track area with MSS.
The water thus stands approximately
15cm above the level of the elastic bearing. There was no effective draining
available for the section of track passing
through the depression.
This presented the opportunity toinvestigate the influence of standing water on
the insulation performance of the MSS in thevery same section that was being examinedwith regard to the long-term effectiveness ofthe vibration insulation measure (‘MSS after
30 years of operation’ project).

Long-term effectiveness of theMass-Spring System – measurement
results in residential buildings
To demonstrate the effectiveness of theMSS, immissions measurements were taken in
the basements.
In 1985 the maximum vibration velocitiesof the passing trams recorded at the various
measuring points inside the buildings andin the tunnel were used to assess the vibrations.
Back then the values had to be determinedmanually using analogue recordings on
Measuring equipment in the measurement section with mass-spring system (MSS)

Railway Review
60 European
VOLUME 22, ISSUE 6, 2016

paper strips, whereas today this is all per -S U B S C R I B E O N L I N E A T:

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NOISE & VIBRATIONSSUPPLEMENT
formed digitally thanks to advanced measuring technology.
To obtain a meaningful comparison of
the measurement data from 1985 and 2015,
only measurements for the ‘Tram 2000’
type were considered in the assessment, asmeasurements had been recorded for thesetrams in 1985.
Table 1 shows a comparison of the maximum vibration velocities measured at themeasuring points in the basements of the buildings to be protected in 1985 and 2015. Results
are displayed for the three spatial directions(x, y, z) as well as the resultants (R).
The maximum vibration velocities recorded
for all directional components in the basementsof the residential buildings and their resultants
lie well below the sensitivity limit of 0.1 mm/s to0.2 mm/s (strictly speaking this is also
dependent upon the frequency and individual
human perception).
As the results show, the MSS is still
completely effective after 30 years ofoperation. All in all, the vibration velocities
Standing water in the longitudinal groove of the mass-spring system (MSS) section, water levelapproximately 20cm

recorded were extremely low. It can be seenthat the measured immission values have notincreased at any location or in any spatial direction; the values

Evaluation

today are even significantly lower. This improvement is most likely,

The investigation shows that the bearing of the Sylomer® material in

however, the result of the more accurate measuring and evaluationwater has no negative effect on the vibration reduction of the system.

technology in use today.

The scatter for the insertion loss is the result of varying parameters,

Overall, this is resounding proof that the vibration-reducing effectat the immission location is still in full force – the MSS tested in
Schwamendingen, Zurich, has not lost any of its performance even after
30 years of operation.

such as the recording of different tram types, rolling stock, speeds andvarious other factors that are difficult to record.
The slight difference between the insertion loss curves for bothtracks can be attributed to influencing factors such as differing railroughness, welded joints, etc.

Long-term effectiveness of the MSS –measurement results determining the insertion loss

tunnel in Schwamendingen, Zurich, shows an excellent insulation

To demonstrate the current effectiveness of the MSS, the insertion loss

performance. The 30-year old MSS also conforms to the latest

was determined based on the difference between the one-third octave

requirements and technological standards. The vibration insulation

spectra of both superstructures ‘with MSS’ and ‘without MSS’. The

measure is in perfect working order.

The insertion loss determined for the MSS with Sylomer® in the tram

insertion loss is a mass that describes the effect of an elastic element –in this case the elastic bearing of slabs on Sylomer® – installed in a given
situation involving a vehicle, superstructure and substructure.
Graph 1 on page 60 shows the insertion loss with thecorresponding scatter of the MSS for track 700 (without water)
averaged over all passing trams, as well as the insertion loss of the MSS
for track 800 (with water).

Table 1: Comparison (1985 and 2015) of maximum vibration velocities measured atpoints in the basement areas of buildings to be protected
Building 1 – Basement

Building 2 – Basement

Yearxmm/s

ymm/s

zmm/s

Rmm/s

1985

0.02

0.05

0.05

0.06

2015

0.008

0.006

0.010

0.011

xmm/s

ymm/s

zmm/s

Rmm/s

0.01

0.04

0.02

0.05

0.006

0.006

0.011

0.012

Dr. Adrian Egger studied geophysics at ETH Zurich. For
the past 20 years he has been a project leader in the field ofvibration protection at various engineering consultancies
in Zurich. His specialities are measuring and forecasting
technology. Since 2015 Adrian has been working at
Trombik Ingenieure AG in Zurich as a Company
Executive and he is responsible for the Vibrations andStructure-Borne Sound Division.
Markus Heim studied technical physics at the Vienna
University of Technology and has been a Member of theR&D Department at Getzner Werkstoffe GmbH for
25 years. His area of expertise is in vibration engineering,in particular vibration measuring technology. He is alsoheavily involved in the development and testing of newelastomer materials, components and systems and takes
part in research projects. Markus’ international experiencein effectiveness studies and long-term references for railway projects
completes his portfolio.

S U B S C R I B E O N L I N E A T:

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VOLUME 22, ISSUE 6, 201661