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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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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
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)
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.
Bridge Weigh-In-Motion Typical ‘Measured’ Response
Bridge Weigh-In-Motion Theoretical Response x
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
Model Description Truck Model - 8 Degrees of Freedom
Model Description Data Used for simulations of truck crossings... Statistical Data for - GVW & Velocity - Axle Spacing - Axle Weights
Model Description Data Used for simulations of truck crossings... Carpet Profile
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%
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.
Assessment Dynamic Ratio Trends in ADR with Time... source: Rattigan (2007)
Assessment Dynamic Ratio Trends in ADR with Time... source: SAMARIS (2006)
Assessment Dynamic Ratio Trends in ADR with Time...
Bridge Weigh-In-Motion Accuracy Inferred Static Response
Bridge Weigh-In-Motion Accuracy Inferred Static Response
Bridge Weigh-In-Motion Accuracy Inferred Static Response Error in Maximum Static
Bridge Weigh-In-Motion Accuracy Error in prediction of ADR
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...
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.