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

3Pavement design

Source: Department of Transport, Planning and Infrastructure, SA

4

1979 1987 1992 2004 20082010

2012

5

Guide to Pavement Technology Part 2Pavement Structural Design

2Artists impression2017

6Pavement design

Source: BPW Transpec

7Traffic load distribution

8Rigid pavements

Source: Roads and Maritime Services, NSW

9Rigid design calculations

10Example calculation

11Detailing

Source: Australian Society for Concrete Pavements

12Flexible pavements

Source: Austroads

13

AASHO Road TestAASHO Road Test

Source: AASHO

14Traffic load distribution

15

80 kN

Standard Axle

equivalent Standard Axle Repetitions

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

17

𝑆𝐴𝑅 =

𝑖=1

𝑚𝐿𝑖𝑆𝐿𝑖

𝐿𝐷𝐸

𝐸𝑆𝐴 =

𝑖=1

𝑚𝐿𝑖𝑆𝐿𝑖

4Equivalent

Standard

Axles

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

19Calc. response under Standard Axle

20Design process

Austroads

traffic load distribution +

HVAG count

SAR5 (SAR7, SAR12)

Model candidate structure

with Standard Axle

Allowable loading cf. SAR5

2012

21

𝑆𝐴𝑅 =

𝑖=1

𝑚𝐿𝑖𝑆𝐿𝑖

𝐿𝐷𝐸

Independent of pavement structure

22Design relates performance to strains

Source: Austroads

23

Guide to Pavement Technology Part 2Pavement Structural Design

2Artists impression

(ESAs not dead yet)

24Research

25

Axle-strain method

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

28

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

31

Source: Austroads

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

34Example comparison

250

275

300

325

350

2012 2017

Total asphalt thickness [mm]

C320

35Policy & asset management

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

40

Looking forwards

42

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)

45Methods of assessing bridge loading

Source: NTC (2007)

46

47On-board mass measurement & reporting

Source: Australian Road Research Board

48

Source: Australian Road Research Board

49

50Traffic speed deflectometer

Source: Danish Road Directorate

51iPAVe

Intelligent Pavement Assessment Vehicle

Source: Australian Road Research Board

52

53

• Number plate recognition

• Precise vehicle classification

• Accurate axle mass measurement

Integration

Source: CEOS

54Real time feed for enforcement

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

56

Thank you michael.moffatt@arrb.com.au