influence of the accuracy of a bridge weigh-in-motion system on the determination of a bridge...
TRANSCRIPT
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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 DowlingArturo GonzálezEugene 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
0 5 10 15 20 25 30 35 40-2
0
2
4
6
8
10
12
14
16x 10
5
First Axle Distance (m)
Ben
ding
Mom
ent
(Nm
)
Bridge Weigh-In-Motion
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Theoretical Response
0 5 10 15 20 25 30 35-1
0
1
2
3
4
5
6
7
8
9
10Influence Line Ordinates
Distance (m)
Influ
ence
Lin
e O
rdin
ate x
Bridge Weigh-In-Motion
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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
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...
0 0.4 0.8 1.2 1.6 2 2.4 2.8 3.2 3.6
x 105
1
1.02
1.04
1.06
1.08
1.1
1.12
1.14
No. of trucks
AD
R
0 20 40 60 80 100 120 140 160 180
1
1.05
1.1
1.15
1.2
1.25
1.3
1.35
x 106
No. of Days
Max
BM
ADR
Max Dynamic
Max Static
0 5 10 15 20 25-0.5
0
0.5
1
1.5
2
2.5
3
3.5x 10
5
First Axle Distance (m)
Ben
ding
Mom
ent
(Nm
)
Total
Correct StaticInferred Static
Assessment Dynamic Ratio
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Inferred Static Response
0 5 10 15 20 25 30 35 40-2
0
2
4
6
8
10
12
14x 10
5
First Axle Distance (m)
Ben
ding
Mom
ent
(Nm
)
Total
Correct StaticInferred Static
Bridge Weigh-In-Motion Accuracy
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Inferred Static Response
0 5 10 15 20 25-0.5
0
0.5
1
1.5
2
2.5
3
3.5x 10
5
First Axle Distance (m)
Ben
ding
Mom
ent
(Nm
)
Total
Correct StaticInferred Static
Bridge Weigh-In-Motion Accuracy
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Inferred Static Response
12 14 16 18
2.2
2.4
2.6
2.8
3
3.2
x 105
First Axle Distance (m)
Ben
ding
Mom
ent
(Nm
)
Total
Correct StaticInferred Static
Error in Maximum Static
0 5 10 15 20 25-0.5
0
0.5
1
1.5
2
2.5
3
3.5x 10
5
First Axle Distance (m)
Ben
ding
Mom
ent
(Nm
)
Total
Correct StaticInferred Static
Bridge Weigh-In-Motion Accuracy
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Error in prediction of ADR
0 1 2 3 4 5 6 7 8
x 104
1
1.01
1.02
1.03
1.04
1.05
1.06
1.07
1.08
No. of Trucks
AD
R
Correct & Inferred
Exact
Inferred
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.