Bridge safety after
the Genoa accident
movements and vibrations,
these systems permit
conclusions about stress
and possible corrosion of
the structure.
The Kistler Group offers
tried-and-tested products that
are suitable for all methods of
bridge monitoring: products
that help to preserve valuable
infrastructure and make it safe.
Kistler accelerometers are
specifically designed for bridge
health monitoring and are
deployed on bridges worldwide
to measure influences caused by
traffic, wind, and temperature
fluctuations. Measurement
systems of this sort are installed
on the Great Belt Bridge across
the Baltic Sea in Denmark; in
bridges over the Yangtze River
in China; and in the Mississippi
in the US. For example, 26
Kistler accelerometers are
operating on the Interstate 35W
in Minneapolis (Minnesota),
built in 2009 to replace the
collapsed bridge over the river.
Twelve of these sensors measure
vibrations in the center of the
concrete piers. Fourteen more
highway bridges. Most of them
were built shortly after the
Second World War and they
have an average lifespan of
about 70 years. The situation is
similar in Germany, where
experts have warned that many
bridges are in need of
restoration. How can these
structures be monitored
efficiently? How can their
maintenance be properly
targeted? And how can
maximum safety be ensured?
Checking bridge conditions
There are three different ways to
tackle these issues. The first is to
protect the bridge by preventing
heavy vehicles from crossing it.
The second is to measure the
vehicles’ axle loads per unit of
time. Thirdly, changes to the
bridge itself can be monitored.
Measurement systems based on
accelerometers can collect data
about critical changes to the
structure and ‘health’ of the
bridge: this method is known as
structure health monitoring
(SHM) or bridge health
monitoring. By recording
Technology Profile |
Infrastructures are aging – and
at the same time, traffic
volumes are increasing. This
creates hazardous situations,
but with the right technologies,
the risk can be reduced.
Vibration measurements can
supply valuable data about the
exact condition of a bridge;
meanwhile, weigh-in-motion
(WIM) systems make it possible
for comprehensive data to be
collected and for vehicle access
to be as appropriate.
The Morandi Bridge near
Genoa, Italy, collapsed in the
summer of 2018. The four-lane
viaduct was part of the A10
autostrada, an arterial route that
carries heavy traffic. This
accident in the heart of Europe
claimed 43 lives, but the cause
has not been clarified beyond
doubt. Was a design error to
blame? Was inadequate
maintenance responsible? Could
the accident have been
prevented – and if so, how?
We will have to wait for the
official investigative report
from the Italian authorities
to get answers.
Road bridges often have
complex and interrelated
infrastructure problems. The
Genoa accident is the tip of the
iceberg: many other bridges
collapse without claiming
victims, or without attracting
public attention. In the US alone,
for example, there are 578,000
| Need to know
Kistler is a Swizerlandbased
organization
that manufactures:
Traffic Technology International July/August 2019
www.TrafficTechnologyToday.com
062
accelerometers are distributed
throughout the structure to
perform long-term modal
analyses and to monitor the
structure’s natural frequency.
The success of these
measurements is critically
dependent on factors such as
measurement sensitivity,
frequency range, temperature
stability and linearity. Kistler’s
capacitive MEMS and
piezoelectric IEPE sensors offer
technologies to suit different
application conditions. IEPE is
ideal for smaller structures and
higher frequencies, while MEMS
is useful for larger structures
and DC (direct current) or lowfrequency
signals. Additional
parameters that require
specification include cable
lengths, EMC protection and
temperature range/stability.
Preventing damage
Accidents such as those in
Genoa and Minneapolis can be
prevented in the future by
deploying suitable
accelerometers as components of
integral measurement systems
that also include anemometers
(wind gauges), strain sensors,
linear potentiometers, GPS and
other equipment. Another key
component of measurement
systems for bridges is a WIM
system that can deliver detailed
information about stress exerted
by commercial vehicles and
their loads.
WIM systems by Kistler
measure the weight of vehicles
on the road while they are
traveling. They are based on
sensors that can be installed
directly into the road paving for
an unlimited number of lanes in
each direction of travel, with
immediate evaluation of the
> Accelerometer Sensors
> Torque Sensors
> Pressure Sensors
> Weigh-in-motion systems
Left: Accelerometers
measure vibrations in bridges
and allow their structural
state to be monitored
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