1. 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

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

3. 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)

4. 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

5. Typical ‘Measured’ Response Bridge Weigh-In-Motion

6. Theoretical Response x Bridge Weigh-In-Motion

7. 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

8. Truck Model - 8 Degrees of Freedom Model Description

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

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

11. 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

12. 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

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

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

15. Trends in ADR with Time... Assessment Dynamic Ratio

16. Inferred Static Response Bridge Weigh-In-Motion Accuracy

17. Inferred Static Response Bridge Weigh-In-Motion Accuracy

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

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

20. 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...

21. 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.