2024 - 2025
Christos Georgakis
Vitor Diniz Pinto
Francesco Ricciardelli
Jasna Jakobsen
Cristoforo Demartino
Robert Soltys
+1 more
2024 - 2025
Testing of Rain-Wind Induced Vibrations for cable surface modifications
ERIES-RWCASUMO
Project Report
Dataset Description
This dataset includes that from a passive-dynamic rain-wind induced vibration (RWIV) test of a plain cylinder in a 1-DOF rig. The degree of freedom is the in-plane direction (vertical translational motion). The test model is a 5.5m long stay cable High-Density Polyethylene (HDPE) outer pipe. Different pipes are tested: a plain cylinder, a cylinder with a helical fillet, a cylinder with parallel rings. The effects of the cable surface modification on rain-wind induced vibration is investigated for different wind velocities. Acceleration and displacement of the specimen are the main measurements of the tests, however other quantities are measured in order to control the tests.
Specimens
1. Description of the setup
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The setup consist of a suspension rig for a sectional model of a bridge stay cable. The model is suspended with in-plane springs, in the in-plane direction, and drag wires in the out-of-plane direction.
The setup is placed in the wind tunnel with a yaw angle of 30° (0° = wind parallel to cable horizontal projection), and inclination angle of 30°.
Rain and wind have been reproduced together in configurations where the rain intensity was kept constant and the wind speed varied.
1. description of the wind tunnel
Jules Verne wind tunnel is a closed loop installation with a power, from six fans, of 3 MW reulting in the high speed test section of 6m wide and 5m high in wind speeds up to 75m/s.
In this high speed test section the wind speed is measured by mean of a Pitot tube, which can be completed when rain is reproduced by a vane anemometer, not sensitive to water drops.
Temperature and humidity of the air in the wind tunnel are measured by mean of an thermo-hugro-barometer, the barometric pressure is measured outside the wind tunnel. they serve as calculating the air density at the time of the experience.
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Instrumentation
Laser displacement transducers: Bottom end of the specimen (in-plane only)
Accelerometers: Both ends of the specimen (in-plane and out-of-plane)
Rain intensity sensor: Disdrometer, OTT Parsivel²
Other sensors: Wind velocity (vane anemometer), temperature, humidity, atmospheric pressure, air density, rain intensity.
2. description of the rig
The suspension rig was built in order to replicate the dynamic characteristics of a stay cable. This is a sectional model test, therefore the model had the same diameter as a common bridge stay cable, but with a reduced length of 5.5m. The HDPE pipe had a stiff steel inner core so that no bending is expected to occur within the target frequency of 1 Hz.
The model was suspended in the rig with in-plane springs. The stiffness of the springs were chosen to get a frequency of 1.1 Hz, similar to a typical stay cable.
In the out-of-plane direction, drag wires were used to restrain this vibration direction, since the aim was to reproduce RWIV in the in-plane direction. However, a small spring was still used, in parallel to the drag wire, so that there is pretension of this drag wire.
Longitudinal wire were used to restrain axial motion of the cable and compensate gravity to keep the vertical spring perpendicular to cable axis.
The inclination angle chosen was 30°, and the yaw angle of 30° (0° = wind parallel to the cable horizontal projection).
Instrumentation
none
3. rain simulation
The rain simulation was done with several sprinklers attached to a steel wire following the same inclination and yaw as the stay cable, however 20 cm higher than the specimen, in order to reduce disruption of the wind from the rain simulation system. The sprinklers were spaced 50 cm from each other.
Measurement of rain intensity using a disdrometer was carried out before the dynamic tests. The rain intensity is assumed constant in all tests, with value: [ADD]
Instrumentation
Disdrometer is PARSIVEL² from OTT
Sprinklers are from GARDENA , Micro Mist Nozzles, at a distance of 1m.
4. surface preparation
The cables were sprayed with dry graphite lubricant (model L-50 Unican Grafit Spray). Afterward, soot from a diesel engine was used as added surface preparation
Instrumentation
none
2. plain cylinder
2
The section model tested is a 5.5m long and 180mm diameter HDPE pipe that is used for stay cables. Therefore, this model represents accurately the aerodynamic characteristics of a prototype of a stay cable.
This specimen is a plain model, which means there is no cable surface modification.
1. free decay test
excitation of the model by hand, then measure the decay of amplitude to estimate the structural damping of the system
Instrumentation
same as other experiments
2. rain + wind tests
The model was subjected to rain and wind. There was no other type of external excitation. Different wind velocities were used in order to measure the vibration of the model.
Instrumentation
same as other experiments
3. cylinder with helical fillet
2
The section model tested is a 5.5m long and 180mm diameter HDPE pipe that is used for stay cables. Therefore, this model represents accurately the aerodynamic characteristics of a prototype of a stay cable.
This specimen is a cylinder with helical fillet, which is designed to improve the rain-wind induced vibration response, due to disruption of the rain rivulet.
1. free decay
excitation of the model by hand, then measure the decay of amplitude to estimate the structural damping of the system
Instrumentation
same as other experiments
2. rain + wind tests
The model was subjected to rain and wind. There was no other type of external excitation. Different wind velocities were used in order to measure the vibration of the model.
Instrumentation
same as other experiments
4. cylinder with rings
2
The section model tested is a 5.5m long and 180mm diameter HDPE pipe that is used for stay cables. Therefore, this model represents accurately the aerodynamic characteristics of a prototype of a stay cable.
This specimen is a cylinder with rings, which is designed to improve the rain-wind induced vibration response, due to disruption of the rain rivulet.
1. free decay
excitation of the model by hand, then measure the decay of amplitude to estimate the structural damping of the system
Instrumentation
same as other experiments
2. rain + wind tests
The model was subjected to rain and wind. There was no other type of external excitation. Different wind velocities were used in order to measure the vibration of the model.
Instrumentation
same as other experiments
Project Metadata
Rights
Creative Commons Attribution 4.0 International.
CC BY 4.0
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