Considering multiple-axle group loads in mechanistic design of bound pavements Michael Moffatt.
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Transcript of Considering multiple-axle group loads in mechanistic design of bound pavements Michael Moffatt.
![Page 1: Considering multiple-axle group loads in mechanistic design of bound pavements Michael Moffatt.](https://reader037.fdocuments.in/reader037/viewer/2022110207/56649d1a5503460f949ef688/html5/thumbnails/1.jpg)
Considering multiple-axle group loads in mechanistic design of bound pavements
Michael Moffatt
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Source: Department of Planning, Transport and Infrastructure, South Australia
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80 kN
Standard Axle
equivalent Standard Axle Repetitions
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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
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Fatigue testing
flexural fatigue testingusing trapezoidal beam
displacement controlduring testing
no rest periods
simulated axles had equal peaks
8
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non-linear elastic support materials
localised stress/modulus states
superpositioning of responses
3D FEM
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Asphalt
Crushed rock
Subgrade
Pavement structures
1000 MPa 3000 MPa5000 MPa
High quality crushed rockLower subbase
Highly plastic clay (CBR 3%)Sand (CBR 15%)
50 100 200 300 mm
200 400 600 mm
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• Equating damage by strain (+ superposition) varies withpavement structure
• thicknesses
• modulus
• Single load equivalency values unsuitable
• Model traffic spectrum, and assign damage to each combination of axle group and load
• same as for concrete design
Implementation in the guide
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Design processAustroadstraffic load distribution + HVAG count
SAR5
Model candidate structure with Standard Axle
Allowable loading cf. SAR5
Summed peakstraffic load distribution + HVAG count
Model candidate structure with axle types/loads in TDL
Sum damage (want ≤ 100 %)
Austroads Summed peaks
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pulse width rest
250 ms250 ms
(a) Haversine
(b) Single axle
(c) tandem
(d) tri-axle
(e) quad-axle
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• conclude that relative damage is the same as number of axles in group
• same procedure as for asphalt
FindingsGroup damage relative to single axle
Groups Relative damage
2 2.4
3 2.8
4.1
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Design example
1 x 108 HVAG
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Asphalt
Crushed rock
Subgrade
Candidate structure
3000 MPa
CBR 7 %
340 mm
300 mm
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Reference load: 135 kN
XX YY
58.2 43.0XX YY
60.7 44.2
XX YY
58.2 43.0XX YY
60.7 44.2
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Further information
Seek me out today.
26th ARRB Conference paper.
www.arrb.com.au/ARRB-
Conferences
Research Report for Austroads in press.
PhD thesis in pre-pre-press.Thank youwww.arrb.com.au