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Vehicle mass data for pavement design
and asset managementWeigh-In-Motion Forum, September 2017
Dr Michael Moffatt
2
• Pavement design
– Rigid pavements
– Flexible pavements
• Asset management
• Looking forwards
Overview
16
Axle type
Standard
group load
[kN]
single axle – single tyres 53
single axle – dual tyres 80
tandem – dual tyres 135
triaxle – dual tyres 181
quad-axle – dual tyres 221
Failure mechanism LDE
asphalt fatigue 5
cemented material fatigue 12
total deformation 7
𝑆𝐴𝑅 =
𝑖=1
𝑚𝐿𝑖𝑆𝐿𝑖
𝐿𝐷𝐸
18
Axle type
Standard
group load
[kN]
single axle – single tyres 53
single axle – dual tyres 80
tandem – dual tyres 135
triaxle – dual tyres 181
quad-axle – dual tyres 221
Failure mechanism LDE
asphalt fatigue 5
cemented material fatigue 12
total deformation 7
𝑆𝐴𝑅 =
𝑖=1
𝑚𝐿𝑖𝑆𝐿𝑖
𝐿𝐷𝐸
20Design process
Austroads
traffic load distribution +
HVAG count
SAR5 (SAR7, SAR12)
Model candidate structure
with Standard Axle
Allowable loading cf. SAR5
2012
23
Guide to Pavement Technology Part 2Pavement Structural Design
2Artists impression
(ESAs not dead yet)
26
Guide to Pavement Technology Part 2Pavement Structural Design
2Artists impression
2017 axle strain method
Removes SARs
Calculates damage – from strains –
caused by each axle in TLD
Approach aligns with that for rigid
pavements
27Design process
Austroads
traffic load distribution +
HVAG count
SAR5
Model candidate structure
with Standard Axle
Allowable loading cf. SAR5
aaaaa
traffic load distribution +
HVAG count
Model candidate structure
with axle types/loads in TDL
Sum damage (want ≤ 100 %)
2012 2017
29
Axle group
load (kN)
Expected group
repetitions
Axles in
group
Critical strain
(𝝁𝒎/𝒎)
Allowable
group repetitions
Damage
10 3 740 2 9.6 6.31 x 1012 5.92 x 10-10
20 14 905 2 19.3 1.92 x 1011 7.75 x 10-8
30 16 167 2 28.9 2.55 x 1010 6.33 x 10-7
40 51 204 2 38.5 6.09 x 109 8.41 x 10-6
50 168 246 2 48.1 2.00 x 109 8.42 x 10-5
60 246 335 2 57.8 7.98 x 108 3.09 x 10-4
70 283 346 2 67.4 3.70 x 108 7.66 x 10-4
Tandem group example
30
Guide to Pavement Technology Part 2Pavement Structural Design
2Artists impression
Simplifications:
– axles act independently
120 kN tandem = 2 x 60 kN single
– strains increase linearly with axle load
– requires two response-to-load calcs
32
Guide to Pavement Technology Part 2Pavement Structural Design
2Artists impression
Effect of 2007 changes for bound materials
Cemented materials: Similar thickness
Lean-mix concrete: Similar thickness
Asphalt: Reduced thickness
for heavy-duty
structures
33Example comparison
wearing course
levelling course
base course
lower base course
granular subbase course
selected fill
in situ subgrade
SMA:A15E
AC14:A15E
AC20:C320
AC20:C320
40 mm
40
180
60
150
300
36Network-level life-cycle costing example
• Freight Axle Mass Limits Investigation Tool (FAMLIT)
– marginal cost of road wear from heavy vehicles
• informs road asset managers of expected maintenance
and rehabilitation costs resulting from a change in traffic
loading
– maintenance standards
– traffic volumes
– construction standards
– climate/location, etc.
36
37Key inputs & factors
– different road pavement designs, materials,
construction, strength
– maintenance scenarios
– traffic fleet variations
– vehicle type
– vehicle loading
– vehicle volumes
37
38Life-cycle cost model
38
Road description
Traffic loading
Models
Deterioration Works effect
+ Model settings+
Annual cost
Works trigger
Total cost
Over a 50 year analysis period
39Load-wear-cost model
39
. . .
Mass 1 Mass 2 Mass 3
1 2 3 . . . Mass
$
< <
FAMLIT WLCC FAMLIT WLCC FAMLIT WLCC$ $ $
• To convert a life-cycle cost into a load-wear-cost you need multiple life-cycle cost at different loads
• Input a different loading scenario (change in axle group mass) into FAMLIT and generate another cost associated with that load
43Regulatory consideration of bridges
Most
access
Least
access
‘As of right’ vehiclesComply with all regulations,
and state-based axle load limits
All areas of the road
network (unless
indicated by
signage)
PBS vehiclesComply with PBS rules
Areas of the relevant
PBS network, or as
controlled by the
asset owner
Restricted access vehiclesComply with state-based policies.
Longer/heavier than ‘as-of-right’
Areas of the relevant
restricted access
network
Permit-based vehiclesNon-compliance with regulations
Restricted accessed
based on individual
permits
Source: Australian Road Research Board
44Methods of assessing bridge loading
• The bridge formula aims to limit the total
mass across adjacent axle groups
Source: NTC (2012)
53
• Number plate recognition
• Precise vehicle classification
• Accurate axle mass measurement
Integration
Source: CEOS
55
• Real time feed for
enforcement
• Accurate determination of
axle loads
• National integrated data set
for multiple stakeholders
Mass measurement point
Source: Roads and Maritime Services, NSW