Transcript MOD6 Class 4 Pavemen..

PAVEMENT CONDITION INDICES
Instructional Objectives
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
Historic development of pavement condition
indices
The basic functions of condition indices in
PMS
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Different types of condition indices
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Development of a pavement condition index
Condition Surveys
Ride Quality, Surface Distress, Rutting
Pavement Indices
Pavement Wheel Path Profile
Ride Quality Index
IRI
Pavement Surface Distresses
Surface Distress Index
Rutting
Average Pavement Rut Depth
Structural Capacity
Deflections
Structural Capacity Index
Converts collected data to single value
(over the pavement section)
Need for Condition Surveys
Ride Quality Index
 Measure Pavement Wheel Path Profile(s) to assess
Pavement Ride Quality
 Convert Pavement Wheel Path Profile (L&R) to
Pavement Ride Quality Indices (IRI)
0.1 mile
IRI
Need for Pavement Distress Indices
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Trigger treatments
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Calculating life-cycle costs
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Evaluate network conditions
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Compare roads with different distresses
Pavement Condition Indices
Development
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Transform pavement condition data into
pavement condition indices
Deduct values developed for various levels of
distress severity and extent
Two basic approaches
- Expert opinion
- Engineering criteria
Present Serviceability Rating
PSR
5.0 to 4.0
3.9 to 3.0
2.9 to 2.0
1.9 to 1.0
0.9 to 0.0
Description
Very Good
Good
Fair
Poor
Very Poor
Based on Verbal Description of Distresses and Ride Quality
Present Serviceability Index
PSI = 5.02-log(1+SV)-1.38(RD)2-0.01(C+P)1/2
Where:
PSI
= Statistical estimate of the Mean PSR
SV
= Slope variance (roughness)
RD
= Rut Depth
C
= Cracking (ft2 / 1000 ft2)
P
= Patching (ft2 / 1000 ft2)
Pavement Condition Indices Development
Computed using a very simple deduct based
formula:
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PCI = PCImax - ΣDeduct Value
Example
100 - 40 = 60
Deduct Value Table
From Expert Opinion
Severity Extent ( % )
None
1 – 10
10 - 25 25 - 50 > 50
Low
0
20
30
40
50
Medium
0
35
40
60
75
High
0
50
60
80
100
Deduct Value Graph
From Expert Opinion
Deduct Values
Deduct Value Level
100
80
LOW DV
MOD DV
Severe DV
60
40
20
0
0
10
20
30
40
50
Extent
60
70
80
90
100
Engineering Criteria Approach:
Index Scale
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Scales used for condition index
Scales chosen to meet agency needs and
perceptions
Typical scales are 0-100, 0-10, 0-5
Engineering Criteria Approach:
Threshold/Trigger Value
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Index value representing unacceptable
pavement condition
Typically taken as middle of an index scale,
such as 50 (0-100 scale) or 2.5 (0-5 scale)
May be set to represent a range such as 40
to 60 (0-100 scale) or 2 to 3 (0-5 scale)
Engineering Criteria Approach:
Engineering Criteria
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Pavement distress level (severity, extent),
considered unacceptable
Amount of distress for each severity level
where action should be taken to correct
distress
May be numerically different for various types
of distress
Engineering Criteria
Example
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Use a 100 to 0 Scale
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Set Threshold/Trigger Condition Value at 50
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Set Engineering Criteria
90% Low Severity Cracking
25% Medium Severity Cracking
15% High Severity Cracking
Engineering Criteria
Example
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Develop Plot of Deduct Values
- All three severities start at 0 and pass through the
threshold value of 50 at the engineering criteria
selected
- In this example they pass through the threshold
value of 50 at 15%, 25%, and 90% for low, medium
and high severity cracking
Development of Deduct Values
Deduct
Example Deduct Values
100
90
80
70
60
50
40
30
20
10
0
Threshold deduct value
Low
Med.
High
Engineering criteria
0
15
25
20
40
60
Extent (%)
80
90
100
Engineering Criteria
Example
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Develop Final Deduct Values from relationships
shown on plot
The Deduct Values may be developed as set of
continuous functions which may be shown:
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as a plot of a chart
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as a formula
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as a set of deduct tables
Example Deduct Value Table
(Straight Line approach)
Severity Extent ( % )
None
1 – 10
10 - 25 25 - 50 > 50
Low
0
3
10
21
43
Medium
0
10
35
75
-
High
0
20
70
-
-
Pavement Deduct Values
ASTM D5340 “Paver”
“Based on Engineering Experience”
Deduct Value
100
80
Low
60
Me d.
40
High
20
0
1
10
Extent
100
Pavement Deduct Values
Using Log-Log Chart
Deduct Value
100
Low
10
Med.
High
1
1
10
Extent
100
Current Practices
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Distress info - most variation
- field procedure
- distress definitions
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Little opportunity to exchange information
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Approximately. 80% of agencies use
- distress index
- serviceability index/rating
- priority rating
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No evident trends in development
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67% use composite indices
NJDOT Practice
• Pavement Roughness Index – IRI
• Pavement Distress Indices
– Non-Load Associated Distress Index (NDI)
– Load Associated Distress Index (LDI)
– Surface Distress Index Modified (SDIm)
NJDOT Practice
0.1 mile (528 ft) pavement section
i
1
2
3
4
5
6
7
8
9
10
NWPa
WPL
NWPb
WPR
NWPc
52.8 ft
52.8 ft
52.8 ft
52.8 ft
52.8 ft
52.8 ft
52.8 ft
52.8 ft
52.8 ft
52.8 ft
NJDOT Practice
0.1 mile (528 ft) pavement section
1,75 ft
2.5 ft
3.5 ft
Wheelpath
2.5 ft
Wheelpath
12 ft
1,75 ft
NJDOT Practice
NDI Distress Weights
RC
NDI
Patching
BC/CO
Patching
60
10
Shoulder Condition
10
Cracks
100
Longitudinal Cracks
140
Long Jt Cond
145
Multiple Cracks
150
Trans Jt Cond
145
Transverse Cracks
140
500
Total
500
Shoulder
Condition
Total
100
NDI
NJDOT Practice
LDI Distress Weights
Distress
Distress Weights
LMC
300
Rut
200
NJDOT Practice
Distress Severity-Extent Weights
Severity-Extent Weight
Severity-Extent Weight
1
0.9
0.8
y = 0.01x
y = 0.009x
0.7
0.6
0.5
0.4
0.3
Slight
Moderate
y = 0.008x
Severe
0.2
0.1
0
0
10 20 30 40 50 60 70 80 90 100
Extent
Rut Depth Weight
Rut Depth Wt Value
Rut Depth Wt
250
200
150
100
50
0
0
0.1
0.2
0.3
0.4
Rut depth
0.5
0.6
0.7
NJDOT Practice
Surface Distress Indices
Distress Weight * S  E Weight *Extent
NDI  5  LDI =
100
LDI  5 
rut depth* 400  300* S  E W * Extent
SDIm = 0.8 NDI + 0.2 LDI
100
Questions?