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Bridge Smoothness in Virginia – A Decade in Review
Kevin McGhee, PEAssociate Principal ScientistOH DOT Bridge Rideability Symposium
3/18/2011 2
http://vtrc.virginiadot.org/PubDetails.aspx?PubNo=02-R10
April 2002
3/18/2011 3
Summary/Objectives
• Survey quality of ride on Virginia bridges (and bridge “encounters”)
• Determine/confirm where major ride quality issues exist
• Identify characteristics of bridge design that affect bridge smoothness/roughness
• Develop rudiments of “modern” smoothness provision for bridges
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Bridge Survey - 289 Bridges
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0
20
40
60
80
100
120
140
160
0 100 200 300 400 500 600IRI (in/mi)
Freq
uenc
y
Deck OnlyOverall Bridge SettingAsphalt Pavement
Ride Quality – Freq. Distribution
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Ride Quality by Component
050
100150200250300350400
IRI (
in/m
i)
RoadBefore
FirstJoint
BridgeDeck
LastJoint
RoadAfter
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Roughness Contributions(Matrix of Correlation)
Bef. Jt. 1 Deck Jt. 2 AfterOverall .51 .33 .57 .19 .63
Bef. 1 .22 -.11 -.03 .51Jt. 1 1 .11 .20 .25Deck 1 .14 .02Jt. 2 1 .07After 1
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DESIGN/SERVICE VARIABLES
• Wearing surface• Structure material• Structure type• Abutment type• Deck protection• Deck structure type• Joint type
• Year built• Service carried• Number of lanes• ADT and % Trucks• Length• Maximum span• Skew
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Wearing Surface
• Decks with concrete overlays are smoother than decks with bare/integral concrete
• Decks with bituminous overlays rougher (statistically?) on average
• Approaches to bituminous decks are smoother (statistically!) on average
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0
50
100
150
200
250
Road Before Bridge Deck Road After
Steel Concrete
Superstructure Material
Significant
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0
50
100
150
200
250
Road Before Bridge Deck Road After
Continuous Simple-Span
Superstructure DesignSignificant
Significant
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0.025.050.075.0
100.0125.0150.0175.0200.0
0.00 20.00 40.00 60.00 80.00 100.00 120.00 140.00
Distance (m)
Elev
atio
n (m
m) 1700 mm/km IRI
0.025.050.075.0
100.0125.0150.0175.0200.0
0.0 10.0 20.0 30.0 40.0 50.0 60.0
Distance (m)
Elev
atio
n (m
m) 2350 mm/km IRI
Designed Camber
(150 in/mi)
(110 in/mi)
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Straightedge Simulation
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Straightedge vs IRI
R2 = 0.508
-10%
0%
10%
20%
30%
40%
50%
0 200 400 600
IRI (in/mi)
Dec
k in
Vio
latio
n
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Example “Straightedge” Simulation
-6.0
-5.0
-4.0
-3.0
-2.0
-1.0
0.0
1.0
2.0
3.0
4.0
5.0
70 72 74 76 78 80 82 84
Distance (meters)
Elev
atio
n (m
m)
Left Elev. Right Elev. Left Violation Right Violation
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0
500
1000
1500
2000
2500
3000
3500
0 30 60 90 120 150 180 210 240 270 300 330 360 390 420 450 480
Dist (m)
IRI (
mm
/km
)
19
3
18
30
6
2
1921
1
4
9
28
0
27
0
28
Average Bridge
Average Pavement
Profiles from “exemplary” bridge
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Conclusions
• The roadway immediately before and after a bridge (the “approaches”) exhibit strongly correlated riding quality.
• The roadway before simple-span and concrete bridges is smoother than the approaches before continuous-span, steel-girder bridges.
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Conclusions (cont.)
• Decks with concrete overlays are smoother than decks with bare (integral) concrete wearing surfaces.
• Bridges with asphalt overlays have the smoothest approaching and departing roadway – but the bridge deck!?
• We found no correlation between approach ride quality and bridge deck ride quality.
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Pay Adjustment Schedule# Points Out of
Tolerance in 30-m Section
Pay Adjustment ($/ft2)
5 or less Max. Incent., $1.506 to 10 Incentive, $1.2011 to 20 -21 to 30 Disincentive, $1.0031 to 50 Disincentive, $1.20
More than 50 Subject to corrective action (-$1.50)
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I-295/I-64 Flyover- 0.7 lane-mi.- $62,000 incentives
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Springfield Interchange
- 4 Bridges/6.2 lane-mi.- $423,000 incentives
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Woodrow Wilson Bridge
- 23 Bridges (so far)- 7+ lane-mi.- $632,000 incentives
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Impact on Bridge Smoothness
-20
0
20
40
60
80
100
120
140
0 100 200 300 400 500 600
MRI (in/mi)
Freq
uenc
y
2002 - 2010Pre-2002
172
110
Questions?
