Influence of the Accuracy of a Bridge Weigh-In-Motion System on the Determination of a Bridge Assess...
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Influence of the Accuracy of a Bridge Weigh-In-Motion System on the Determination of a Bridge Assessment Dynamic Ratio. Jason Dowling Arturo González Eugene O’Brien. Quick Overview. - Bridge Weigh-In-Motion Model Description Assessment Dynamic Ratio Bridge Weigh-In-Motion Accuracy.

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Jason Dowling Arturo González Eugene O’Brien

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Jason dowling arturo gonz lez eugene o brien

Influence of the Accuracy of a Bridge Weigh-In-Motion System on the Determination of a Bridge Assessment Dynamic Ratio

Jason Dowling

Arturo González

Eugene O’Brien


Jason dowling arturo gonz lez eugene o brien

Quick Overview

  • - Bridge Weigh-In-Motion

  • Model Description

  • Assessment Dynamic Ratio

  • Bridge Weigh-In-Motion Accuracy


Jason dowling arturo gonz lez eugene o brien

Bridge Weigh-In-Motion

Bridge Weigh-In-Motion systems use instrumented bridges to collect data on the truck fleet at a specific location.

  • - This concept was first proposed by Moses (1979)

  • Strain transducers are attached to the soffit of a bridge

  • Axle detectors are placed on the road surface

  • An algorithm is used to interpret the data

source: WAVE (2001)


Jason dowling arturo gonz lez eugene o brien

Bridge Weigh-In-Motion

  • Moses Algorithm (1979) remains the most popular algorithm used in Bridge Weigh-In-Motion systems.

  • - Based on minimizing the sum of squares of differences between theory and measurements:

Lots of measurements are available during the truck crossing...

- This is utilised to smooth out the dynamic component.


Jason dowling arturo gonz lez eugene o brien

Bridge Weigh-In-Motion

Typical ‘Measured’ Response


Jason dowling arturo gonz lez eugene o brien

Bridge Weigh-In-Motion

Theoretical Response

x


Jason dowling arturo gonz lez eugene o brien

Bridge Weigh-In-Motion

Matrix Solution Technique

Minimizing the Error function,

gives a system of simultaneous equations in Wi

Where {W} is a vector of the desired axle weights


Jason dowling arturo gonz lez eugene o brien

Model Description

Truck Model

- 8 Degrees of Freedom


Jason dowling arturo gonz lez eugene o brien

Model Description

Data Used for simulations of truck crossings...

Statistical Data for- GVW & Velocity

- Axle Spacing

- Axle Weights


Jason dowling arturo gonz lez eugene o brien

Model Description

Data Used for simulations of truck crossings...

Carpet Profile


Jason dowling arturo gonz lez eugene o brien

Model Description

Model Accuracy Classification

COST323 (2002) proposed a method of classification for Bridge Weigh-In-Motion systems

- The models classification under this method is ‘B+(7)’

  • Most individual axle weights predicted within ± 7%

  • Axle group weights & GVW predicted within ± 5%


Jason dowling arturo gonz lez eugene o brien

Assessment Dynamic Ratio

Assessment Dynamic Ratio (ADR) is defined as:

i.e. Not necessarily associated with a single loading event

Recent work has discovered a tendency for ADR to decrease as Return Period, or Load Effect increases.


Jason dowling arturo gonz lez eugene o brien

Assessment Dynamic Ratio

Trends in ADR with Time...

source: Rattigan (2007)


Jason dowling arturo gonz lez eugene o brien

Assessment Dynamic Ratio

Trends in ADR with Time...

source: SAMARIS (2006)


Jason dowling arturo gonz lez eugene o brien

Assessment Dynamic Ratio

Trends in ADR with Time...


Jason dowling arturo gonz lez eugene o brien

Bridge Weigh-In-Motion Accuracy

Inferred Static Response


Jason dowling arturo gonz lez eugene o brien

Bridge Weigh-In-Motion Accuracy

Inferred Static Response


Jason dowling arturo gonz lez eugene o brien

Bridge Weigh-In-Motion Accuracy

Inferred Static Response

Error in Maximum Static


Jason dowling arturo gonz lez eugene o brien

Bridge Weigh-In-Motion Accuracy

Error in prediction of ADR


Jason dowling arturo gonz lez eugene o brien

In Summary:

Moses Algorithm tends to over estimate the maximum static response.

This leads to an underestimation of ADR

Future work will look at further understanding this inaccuracy

With a view to quantifying this or suggesting possible remediation measures...


Jason dowling arturo gonz lez eugene o brien

My Thanks to the 6th European Framework Project ARCHES (Assessment and Rehabilitation of Central European Highway Structures) for funding my work.

Thank you for listening.


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