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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

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Quick Overview - Bridge Weigh-In-Motion - Model Description - Assessment Dynamic Ratio - Bridge Weigh-In-Motion Accuracy

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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 Bridge Weigh-In-Motion source: WAVE (2001)

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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. Bridge Weigh-In-Motion

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Typical ‘Measured’ Response Bridge Weigh-In-Motion

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Theoretical Response x Bridge Weigh-In-Motion

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Matrix Solution Technique Minimizing the Error function, gives a system of simultaneous equations in W i Where {W} is a vector of the desired axle weights Bridge Weigh-In-Motion

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Truck Model - 8 Degrees of Freedom Model Description

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Data Used for simulations of truck crossings... Statistical Data for- GVW & Velocity - Axle Spacing - Axle Weights Model Description

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Data Used for simulations of truck crossings... Carpet Profile Model Description

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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% Model Description

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Assessment Dynamic Ratio (ADR) is defined as: Recent work has discovered a tendency for ADR to decrease as Return Period, or Load Effect increases. i.e. Not necessarily associated with a single loading event Assessment Dynamic Ratio

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Trends in ADR with Time... source: Rattigan (2007) Assessment Dynamic Ratio

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Trends in ADR with Time... source: SAMARIS (2006) Assessment Dynamic Ratio

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Trends in ADR with Time... Assessment Dynamic Ratio

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Inferred Static Response Bridge Weigh-In-Motion Accuracy

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Inferred Static Response Bridge Weigh-In-Motion Accuracy

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Inferred Static Response Error in Maximum Static Bridge Weigh-In-Motion Accuracy

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Error in prediction of ADR Bridge Weigh-In-Motion Accuracy

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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...

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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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