Influence of the Accuracy of a Bridge Weigh-In-Motion System on the Determination of a Bridge...
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Transcript of Influence of the Accuracy of a Bridge Weigh-In-Motion System on the Determination of a Bridge...
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
Quick Overview
- Bridge Weigh-In-Motion
- Model Description
- Assessment Dynamic Ratio - Bridge Weigh-In-Motion Accuracy
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)
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
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
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
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
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%
Model Description
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
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...
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
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
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
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
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
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.