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Vibration
bench
This equipment, partially financed by France's Loire Valley
Regional Council, comprises a 9m x 4m platform, (higher
part of seismic block mechanically isolated of 250 tons),
on which both the actuators and test assemblies can be
anchored. Two pits allow for introducing excitation at
ground level (either by a plate or control table), a TEAM
slip table completes the installation.
Three SCHENCK electrohydraulic servo-jacks with capacities
of 100, 25 and 7 kN, controlled from an INSTRON numerical
console, enable conducting a wide array of dynamic tests
for both research and industry; examples include:
- the dynamic behavior of
instrumentation or structures for calibrating numerical
models,
- equipment evaluation,
resistance to environmental conditions, etc.
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Unit assigned responsibility for equipment operations:
Division for Metrology and Instrumentation (MI)
· Associated research units:
Joint projects with LCPC research laboratories,
such as:
- Division for Road
Maintenance, Safety and Acoustics,
- Division for Pavement
Structures and Materials
· Sectors of activity:
- Structural engineering
- Geotechnical engineering
- Roads
- Environment and
urban engineering
· Contact:
Division
for Metrology and Instrumentation (MI)
· An exemplary application:
· Characterization of SNCF
railway ballast:
The experimental device developed is intended to
simulate actual loading conditions experienced by
the ballast when laid on the railroad; it entails
testing a ballast block, positioned on an elastomeric
deformable base and topped by a concrete railroad
tie. Loadings are applied using a 100-kN jack, via
a load-distribution element that enables applying
forces onto both supporting blocks. Each test consists
of conducting roughly 1 million loading cycles,
with signals providing a realistic simulation of
the loadings produced by train traffic. During the
test, measurements focus primarily on vertical forces
and vertical displacements at the level of both
tie supporting blocks.
The resultant experimental device is displayed in
the following figure.
The ballast blocks were placed in a box 5 m long
´ 1.1 m wide ´ 1 m high. An elastomeric
layer was then set at the bottom of the box, thereby
simulating a platform with a modulus value of E
= 100 MPa.
The ballast was laid in two layers and amounted
to a total volume of approximately 3.3 m3. The first
layer was placed at the bottom of the box; next,
the railroad tie was set on top of this layer and
embedded in a second ballast layer. The longitudinal
extremities of the ballast block were then finished
by 45°-sloped embankments.
Two loading phases were applied during the tests.
An initial phase, which lasted roughly 1 million
cycles, featured a loading frequency of 2.37 Hz
to correspond with train traffic at a speed of 160
km/hr. The loading frequency was subsequently increased
in order to simulate a speed of 320 km/hr and loading
continued for another 250,000 cycles approximately.
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Technical characteristics:
- A 9m x 4m seismic
block
- A 1m x 1m meshed
network of anchorage shafts
- Beam framework construction
elements
- A 1 x 1m horizontal
hydrostatic bearing shaker table
- 4 SCHENCK servo-jacks
of 100, 25 and 7 kN capable of operating simultaneously
- Possible automatic
control of force, displacement, speed, acceleration.
Possible injection of a forced-spectrum signal.
- 3 INSTRON numerical
control channels allowing for either coupled or
uncoupled operations. Each channel is equipped with
an integrated generator, thereby enabling incorporation
of sine wave, triangular, square or external input
loads.
- SIGLAB acquisition
and generation system serving to generate: arbitrary
and random signals, harmonic analyses, FFT, transfer
functions, distortion rate analyses, mode searches,
etc.
- HBM synchronous
multi-channel (24) acquisition system.
· Operational since:
1985
· Application examples:
- Evaluation of the
dynamic behavior of pavement-monitoring vehicles,
- Verification of
sensor characteristics: seismic sensors, contact-free
sensors, piezoelectric-type sensors,
- Study of crack propagation
in a concrete specimen,
- Behavioral characterization
of recycled ballast, within the scope of a research
assignment commissioned by the SNCF Railway Company,
- Resistance of variable-display
panels to environmental conditions.
· Application examples in
other sector:
-Resistance of optical
fiber-packing cabinets to environmental conditions
for the telecommunications industry.
- Comportements dynamiques
et statiques d'aussières en fibres synthétiques
pour plate-forme offshore (contrat IFREMER)
· Associated facilities:
- Climate-controlled
chamber |
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