Active Damping of Suspension Bridges

A. Preumont, D. Alaluf , B. Mokrani

Université Libre de Bruxelles, Brussels, Belgium

AIA15Warsaw

October, 15th , 2015

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Contents

•Motivation•Theory of decentralized IFF control of cable-structures•Space structures (numerical simulation)•Space structures (experiment)•Gamma ray telescope MAGIC•Cable-stayed bridge •Suspension bridge•Conclusion

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Cable-stayed bridge

Suspension bridge

Stay cables in suspension bridges

Auperin, M., Dumoulin, C., Proc. 3rd Int. Workshopon Structural Control (Paris 6-8 July 2000)

Motivation

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Decentralized Collocated IFF control of cable structures

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Maximumachievabledamping:

A.PREUMONT: Vibration Control of Active Structures, 3rd Edition, Springer 2011

Recovering static stiffness: The “Beta” controller

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Beta Controller:IFF Controller:High-pass

filter

Unconditionally stable if:

JPL Microprecision Interferometer testbed (simulation)

2 mmKevlar cables

14%

16%

21%

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ULB free floating truss

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ULB free floating truss Active tendon

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ULB free floating truss(Theory vs. Experiment)

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MAGIC – Major Atmospheric Gamma-ray Imaging Cherenkov Telescope

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Focal length:17 mMirror diameter :17 m Camera Mass: 0.75 tTotal Mass:72 tMirror support: CFR tubesCamera Mast – Stiffened byprestressed cables

M. SMRZ, et al. Active Damping of the Camera Support Mast of a Cherenkov Gamma Ray Telescope, Nuclear Instruments and Methods in Physics Research, A 635 (2011)

Magic Telescope

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Step response at the camera with 4 active cables

Structural model

Camera

Active cablesconfiguration

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Cable-stayed bridge« ACE » project (2000)Laboratory experiment

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« ACE » projectCable-stayed bridge

Sweep-sine excitation

Envelope of the deckdisplacement for various gains

Cable-stayed bridge« ACE » project (2000)

Large scale test (JRC-ELSA)

Auperin, M., Dumoulin, C., Proc. 3rd Int. Workshopon Structural Control (Paris 6-8 July 2000)

Suspension bridge

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Suspension bridge: Seriate footbridge (45°40'18.5"N 9°43'45.2"E)

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8 pedestrians walking on the bridge (measurement point 3)

4 joggers on the bridge (measurement point 5)

3 5

Amax=1.8 m/s2

Amax=4 m/s2

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63.5 m

h=15.6 m

8 m

1.33 m

80.1°

F.E. model of the Seriate bridge

Main cables: D=60 mmHangers: D=16 mm

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Option 1: Four active steel cables of diameter 10 mm between the pylon and the deck

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Option 2: Active cables attached to the catenary

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MSc students Andrea Sangiovanni and Matteo Voltan, from Politecnico di Milano (2015)

Schematic view of the laboratory mock-up

The tension in the hanger is adjustedfrom the measured natural frequency:

Optical device for measuring f

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Mock-up with4 active tendons

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Laboratory demonstrator: comparison between numerical and experimental modes

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Open-loop Transfer FunctionThe two curves refer to different

Natural frequencies of the active cable

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Response to disturbance, z/f with a single loop of control

Cumulative RMS

FRF

Response with a single control loop:Evolution of the RMS response (z) and the

RMS control input (v) with the control gain g

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Response with a single control loop:Root locus reconstruction and comparison with the approximate theory

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Decentralized control with Four independent loopsReponse to disturbance z/f (FRF and cumulative RMS)

No spillover !

Conclusions

• Decentralized active tendon control of cable-structures is possible.

• Simple prediction formulae based on linear models may be used for design.

• The simple performance prediction formulae are supported by experiments.

• The static stiffness deficiency of the IFF can be recovered by high –pass filtering.

• A highly effective control of a suspension bridge may be obtained with few and

small active control cables which do not have to withstand the dead loads.

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Acknowledgements

Prof. Carmelo Gentile from Politecnico di Milano (Italy) for sharing with us the data and the experimental modal analysis of the Seriate Bridge.Prof. Mihaita Horodinca from « Gheorghe Asachi » university of IASI (Romania)for his help in the construction of the bridge laboratory mock-up.MSc students Andrea Sangiovanni and Matteo Voltan, from Politecnico di Milano for conducting the experimental study of the bridge mock-up.