Asphalt Pavement Magazine - September/October 2017 - 43

Perpetual Pavement Design Software
Layer Location
1

3

Bottom

Top

Criteria

Target Units

Target %tile

Actual %tile

Pass/Fail?

Tensile Strain

-257 microstrain

95

99

Pass

-194 microstrain

85

98

Pass

-158 microstrain

75

92

Pass

-131 microstrain

65

82

Pass

-110 microstrain

55

69

Pass

200 microstrain

50

76

Pass

Vertical Strain

Figure 4: Formatted Excel Output - Performance Summary

PerRoad Version 4.3
The newest release of the
software, PerRoad Version 4.3,
fully implements the new design
criteria through redesigned
interfaces within the input and
output program windows. These
new features allow the designer to
select default strain distributions
based on previous studies1,2 or
enter a laboratory-determined
fatigue endurance limit that the
program will use to compute a
control strain distribution.
Figure 1 illustrates the new
strain distribution input interface.
The program's output window has
been modified to accommodate
the new design criteria. The output
table in Figure 2 informs the
designer of whether the criteria
have been met in a simple Pass/
Fail format and adjustments can
be made as needed until all criteria
are satisfied.
The newly added conventional
M-E design features allow the
designer to estimate the design
life based on traditional transfer
functions, which enables
direct comparisons between
conventional and perpetual
design. Figure 3 shows design
curves developed with the
software for a particular set of
input conditions.

The perpetual designs do
not change with traffic volume,
assuming all else is held constant,
because the strain distribution is
only a function of the distribution
of axle loads, not volume. The
M-E designs, however, are highly
sensitive to traffic volume since
strain levels are allowed to occur
at higher levels where damage
accumulation occurs as a function
of the volume of axle loads (i.e.,
more traffic = faster damage
accumulation = greater required
AC thickness). It is also important
to note that the conventional
M-E design curve has no practical
upper limit and will continue
to increase with higher traffic
volumes arriving at impractically
overdesigned pavement structures.
In addition to the input and
output updates in PerRoad 4.3,
the software was also enhanced to
provide an Excel output formatted
ready-to-print. These reports
may be used when developing
a pavement design project and
to document all inputs and
outputs developed in the design
process. Figure 4 illustrates the
performance summary page output
into Excel. AP
Dr. David Timm, P.E., is Professor
of Civil Engineering at Auburn

University. Dr. Nam Tran, P.E., is
Associate Research Professor/Lead
Researcher at NCAT. Dr. Carolina
Rodezno is Assistant Research
Professor/Lead Researcher at NCAT.

References
1. Castro, A.J., N. Tran, M.M. Robbins,
D.H. Timm, and C. Wagner. Further
Evaluation of Limiting Strain
Criteria for Perpetual Asphalt
Pavement Design. In Transportation
Research Record: Journal of the
Transportation Research Board,
No. 2640, Transportation Research
Board of the National Academies,
Washington, D.C., in press, 2017.
2. Tran, N., M. M. Robbins, D. H.
Timm, J. R. Willis, and C. Rodezno.
Refined Limiting Strain Criteria and
Approximate Ranges of Maximum
Thicknesses for Designing LongLife Asphalt Pavements. NCAT
Report No. 15-05, National Center
for Asphalt Technology at Auburn
University, Auburn, Ala., 2015.

Free Software
Download
PerRoad Version 4.3 can be
downloaded free of charge at:
www.AsphaltRoads.org/perroad

Asphalt Pavement Magazine - September/October 2017 * 43


http://www.AsphaltRoads.org/perroad

Table of Contents for the Digital Edition of Asphalt Pavement Magazine - September/October 2017

Chairman’s Commentary
Industry News
Back to Basics: Designed to Perform
NAPA President Mike Acott Talks About Thinlays
Asphalt Pavement Alliance 2016 Perpetual Pavement Awards
PerRoad Version 4.3: Perpetual Pavement Design Software
Tools for the Trade
Industry Calendar
Index of Advertisers/Advertisers.com
Asphalt Pavement Magazine - September/October 2017 - Intro
Asphalt Pavement Magazine - September/October 2017 - cover1
Asphalt Pavement Magazine - September/October 2017 - cover2
Asphalt Pavement Magazine - September/October 2017 - 3
Asphalt Pavement Magazine - September/October 2017 - 4
Asphalt Pavement Magazine - September/October 2017 - 5
Asphalt Pavement Magazine - September/October 2017 - 6
Asphalt Pavement Magazine - September/October 2017 - 7
Asphalt Pavement Magazine - September/October 2017 - 8
Asphalt Pavement Magazine - September/October 2017 - Chairman’s Commentary
Asphalt Pavement Magazine - September/October 2017 - 10
Asphalt Pavement Magazine - September/October 2017 - Industry News
Asphalt Pavement Magazine - September/October 2017 - 12
Asphalt Pavement Magazine - September/October 2017 - 13
Asphalt Pavement Magazine - September/October 2017 - 14
Asphalt Pavement Magazine - September/October 2017 - 15
Asphalt Pavement Magazine - September/October 2017 - 16
Asphalt Pavement Magazine - September/October 2017 - 17
Asphalt Pavement Magazine - September/October 2017 - 18
Asphalt Pavement Magazine - September/October 2017 - Back to Basics: Designed to Perform
Asphalt Pavement Magazine - September/October 2017 - 20
Asphalt Pavement Magazine - September/October 2017 - 21
Asphalt Pavement Magazine - September/October 2017 - NAPA President Mike Acott Talks About Thinlays
Asphalt Pavement Magazine - September/October 2017 - 23
Asphalt Pavement Magazine - September/October 2017 - 24
Asphalt Pavement Magazine - September/October 2017 - 25
Asphalt Pavement Magazine - September/October 2017 - 26
Asphalt Pavement Magazine - September/October 2017 - 27
Asphalt Pavement Magazine - September/October 2017 - 28
Asphalt Pavement Magazine - September/October 2017 - 29
Asphalt Pavement Magazine - September/October 2017 - 30
Asphalt Pavement Magazine - September/October 2017 - 31
Asphalt Pavement Magazine - September/October 2017 - Asphalt Pavement Alliance 2016 Perpetual Pavement Awards
Asphalt Pavement Magazine - September/October 2017 - 33
Asphalt Pavement Magazine - September/October 2017 - 34
Asphalt Pavement Magazine - September/October 2017 - 35
Asphalt Pavement Magazine - September/October 2017 - 36
Asphalt Pavement Magazine - September/October 2017 - 37
Asphalt Pavement Magazine - September/October 2017 - 38
Asphalt Pavement Magazine - September/October 2017 - 39
Asphalt Pavement Magazine - September/October 2017 - PerRoad Version 4.3: Perpetual Pavement Design Software
Asphalt Pavement Magazine - September/October 2017 - 41
Asphalt Pavement Magazine - September/October 2017 - 42
Asphalt Pavement Magazine - September/October 2017 - 43
Asphalt Pavement Magazine - September/October 2017 - 44
Asphalt Pavement Magazine - September/October 2017 - Tools for the Trade
Asphalt Pavement Magazine - September/October 2017 - 46
Asphalt Pavement Magazine - September/October 2017 - 47
Asphalt Pavement Magazine - September/October 2017 - 48
Asphalt Pavement Magazine - September/October 2017 - 49
Asphalt Pavement Magazine - September/October 2017 - 50
Asphalt Pavement Magazine - September/October 2017 - 51
Asphalt Pavement Magazine - September/October 2017 - 52
Asphalt Pavement Magazine - September/October 2017 - Industry Calendar
Asphalt Pavement Magazine - September/October 2017 - 54
Asphalt Pavement Magazine - September/October 2017 - Index of Advertisers/Advertisers.com
Asphalt Pavement Magazine - September/October 2017 - 56
Asphalt Pavement Magazine - September/October 2017 - 57
Asphalt Pavement Magazine - September/October 2017 - 58
Asphalt Pavement Magazine - September/October 2017 - cover3
Asphalt Pavement Magazine - September/October 2017 - cover4
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