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Jason Dowling Arturo González Eugene O’Brien

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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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slide1

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

slide2

Quick Overview

  • - Bridge Weigh-In-Motion
  • Model Description
  • Assessment Dynamic Ratio
  • Bridge Weigh-In-Motion Accuracy
slide3

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)

slide4

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.

slide5

Bridge Weigh-In-Motion

Typical ‘Measured’ Response

slide6

Bridge Weigh-In-Motion

Theoretical Response

x

slide7

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

slide8

Model Description

Truck Model

- 8 Degrees of Freedom

slide9

Model Description

Data Used for simulations of truck crossings...

Statistical Data for - GVW & Velocity

- Axle Spacing

- Axle Weights

slide10

Model Description

Data Used for simulations of truck crossings...

Carpet Profile

slide11

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%
slide12

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.

slide13

Assessment Dynamic Ratio

Trends in ADR with Time...

source: Rattigan (2007)

slide14

Assessment Dynamic Ratio

Trends in ADR with Time...

source: SAMARIS (2006)

slide15

Assessment Dynamic Ratio

Trends in ADR with Time...

slide16

Bridge Weigh-In-Motion Accuracy

Inferred Static Response

slide17

Bridge Weigh-In-Motion Accuracy

Inferred Static Response

slide18

Bridge Weigh-In-Motion Accuracy

Inferred Static Response

Error in Maximum Static

slide19

Bridge Weigh-In-Motion Accuracy

Error in prediction of ADR

slide20

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...

slide21

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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