Bridge Monitoring

Ferpècle bridge (2023/ 2024)

Monitoring goals

Identification of the bridge-parameter values through load testing

Assessment of bridge reserve capacity for serviceability and ultimate limit states

Bridge properties

2 pre-stressed precast concrete girders

Single span of about 35 meters

Built in 1958

Numerical model

3D finite-element model using DIANA

Including non-structural elements to reduce uncertainties

Intervention validation

Understand bridge boundary conditions with distributed fiber optic sensors

Identify material density, concrete elastic modulus and UHPFRC elastic modulus

Main results

One of the first implementation of DFOS on a full-scale bridge

Demonstration that the structural intervention increases signficantly the performance of the bridge

References

N. Bertola, E. Brühwiler, "Transformation of the Static Systems of Bridges with UHPFRC ", Journal of Bridge Engineering, under review.

Acknowledgements

Prof. Brühwiler (EPFL) and Prof. Chatzi (ETH)

Road Authorities in Wallis, IRMOS Technology, SwissInspect

Singapore Flyover Bridge (2016)

The bridge during a static load test (2016)

Bridge modelling

Monitoring goals

Identification of the bridge-parameter values through load testing

Assessment of bridge reserve capacity for serviceability and ultimate limit states

Bridge properties

5 pre-stressed precast concrete girders

Single span of about 32 meters

Built in 1970's

Numerical model

3D finite-element model using ANSYS VM

Including non-structural elements to reduce uncertainties

Model parameters to identify

Deck, parapet and girder Young's moduli

Vertical and rotational stiffnesses of bearing devices

Load tests

3 static tests involving 4 to 6 trucks on specific locations

Ambiant vibration

Free-vibration tests using a single truck at several speeds

Instrumentation

4 deflection measurements using a laser scanner below the bridge and targets on bottom of girders - Static tests

2 Inclinometers on the parapets - Static tests

6 Strain gauges on the bottom of girders - Static tests

10 accelerometers on the parapets - Dynamic tests

Static load tests

Sensor devices used for monitoring

Main results

Although it was built 50 years ago and the traffic increased by 60%, the measurements have revealed that the bridge still presents reserve capacity

A better sensor configuration was possible

References

N.J. Bertola, M. Papadopoulou, D.G. Vernay, I.F.C. Smith, "Optimal multi-type sensor placement for structural identification by static-load testing", Sensors 17 (12) (2017) 2904.
M. Proverbio, D.G. Vernay, I.F.C. Smith, "Population-based structural identification for reserve-capacity assessment of existing bridges", J. Civ. Struct. Health Monit. (2018).
W.-J. Cao, C.G. Koh, I.F.C. Smith, "Enhancing static-load-test identification of bridges using dynamic data", Eng. Struct. 186 (2019).
N.J. Bertola, I.F.C. Smith, " A methodology for measurement-system design combining information from static and dynamic excitations for bridge load testing", J. Sound and Vibr., 463, 114953 (2019).

Acknowledgements

Prof. Smith (EPFL) and Prof. Koh (NUS)

Land Transport Authority (LTA) of Singapore

Comparison of information gain (Joint entropy) of optimal sensor configurations evaluated using the hierarchical algorithm with configurations selected by engineers and calculated using the signal-to-noise ratio.

Exeter Bascule Bridge (2017)

The bridge during a static load test

Bridge drawings and sensor configuration installed

Monitoring goals

Identification of the bridge parameter values through load testing

Assessment of reserve capacity for serviceability and ultimate limit states

Bridge properties

2 Steel girders and aluminum deck

Single span of 17.3 meters

Bascule bridge where the hydraulic jacks influence normal behaviour

Built in 1980's

Numerical model

3D finite-element model using ANSYS VM

Including non-structural elements to reduce uncertainties

Model parameters to identify

Deck equivalent Young's modulus

Rotational stiffness of bearing devices

Vertical stiffness of hydraulic jacks

Load tests

5 static tests involving 1 trucks on specific locations

Instrumentation

11 strain gauges on the bottom of girders and on secondary beams

1 Deflection measurement with a target on the girder and a camera

Static load tests

Main results

The influence of the hydraulic jacks on the structural behaviour has been confirmed using field measurements.

The bridge still presents a reserve capacity although it's a steel bridge built 40 years ago.

A new sensor-placement algorithm using multi-objective approach has been developed.

References

M. Proverbio, N.J. Bertola, I.F.C. Smith, Outlier-detection methodology for structural identification using sparse static measurements, Sensors 18 (6), 1702 (2018).
N.J. Bertola, M. Cinelli, S. Casset, S. Corrente, I.F.C. Smith, A multi-criteria decision framework to support measurement-system design for bridge load testing, Adv. Eng. Inf. 39 (2019).
N.J. Bertola, M. Proverbio, I.F.C. Smith, Framework to assess the value of bridge load testing information for reserve capacity assessment, J. Comp. Civ. Eng., Under review.

Acknowledgements

Prof. Smith (EPFL)

Prof. Kripakaran (Exeter) and Prof. Brownjohn (Exeter)

Full Scale Dynamics Ltd (UK)

Evaluation of several metrics with respect to the number of sensors for measurement-system design. A) Cost of monitoring ; B) Sensor installation costs; C) Ability to detect outliers; D) Loss of information in case of sensor failure.

The research was conducted at the Future Cities Laboratory and Future Resilient Systems at the Singapore-ETH Centre, which was established collaboratively between ETH Zurich and Singapore’s National Research Foundation (FI 370074011-370074016) under its Campus for Research Excellence and Technological Enterprise programme.

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