Download - 03 - Traffic and Equivalent Axle Loads
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Traffic and Axle Loads
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Typical Axle Combinations
Single Axle Tridem AxleTandem Axle
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Typical Weight Limits
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Weigh Stations
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Axle Load Histogram
0
100
200
300
400
500
600
3000-6999 7000-7999 8000-11999
12000-15999
16000-17999
18000-19999
20000-21999
22000-23999
24000-25999
26000-29999
Single Axle Load (lbs)
F
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e
q
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c
y
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Axle Load Histogram
0
50
100
150
200
250
6000-11999
12000-17999
18000-23999
24000-29999
30000-31999
32000-33999
34000-35999
36000-37999
38000-39999
40000-41999
Tandem Axle Load (lbs)
F
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e
q
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c
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Standard Axle Load
Single Axle, Dual Wheels
Source: WSDOT Pavement Guide Interactive CD-ROM
9 kips
9 kips
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GENERIC METHOD
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Mazda Miata
1 consumption per passageMM
dN
Curb weight = 2300 lb
Assume NM = 12,000,000
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Ford Excursion
1 consumption per passageFF
dN
Curb weight = 6300 lb
Assume NF = 200,000
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Standard Vehicle
1 consumption per passageSS
dN
Assume NF = 1,000,000
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Mazda Equivalency Factor
11
M M SMS S M
d N NFd N N
1,000,000 0.08312,000,000
MF
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Ford Equivalency Factor
11
F F SFS S F
d N NFd N N
1,000,000 5.0200,000
FF
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MECHANISTIC METHOD
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Pavement Life (Fatigue)
21
kf tN kAsphaltTensileStrain
AsphaltFatigue
Life
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LEF (Fatigue)
1 sii
kNLEFN
21
kstk
2
2
kit
k sitt
3 k2 6
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Pavement Life (Rutting)
43
kf cN kSubgrade
CompressiveStrain
SubgradeFatigue
Life
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LEF (Rutting)
3 sii
kNLEFN
43
ksck
4
4
kic
k sicc
3.5 k4 4.5
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Pavement Life (Rigid)
4
225,000
tfN MOR
ConcreteModulus of
Rupture
ConcreteTensile Strain
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LEF (Rigid)
sts
ii
MORNLEFN
4it MOR
4
4
itst
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LEF Summary
4 4 4 4
18
i i it t c i
i s s st t c
LLEFL
18-kipStandardAxle Load
MeasuredAxle Load
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AASHTO METHOD
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AASHTO LEF
18
10 10 22 18
18 1log 4.79log 4.33log
xt t t
t x x
W G GLW L L
Flexible Pavements
18
10 10 22 18
18 1log 4.62log 3.28log
xt t t
t x x
W G GLW L L
Rigid Pavements
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Pavement Performance
p
W
i i f Wp p p p
failure
pi
pf
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Pavement Performance
p
W
failure
pi
pf
(failure)
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Pavement Performance
p
W
xi i fx
Wp p p p
pi
pffailure
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Pavement Performance
x xti ft ix
p p pW
p
Wt x
Serviceability Limit
pi
pf
ptp
x
failure
W
x
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Flexible Pavement Performance
xxx
tt 4.2 4.2 1.5
Wp
Wt x
Serviceability Limit
4.2
1.5
ptp
x
failure
W
x
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Flexible Pavement Performance
xxttx
Wp 4.2 4.2 1.5
3.23
25.19 3.23
2
0.0810.41
x
xL L
SN L
9.365.93 4.332
4.792
10 1 x xSN LL L
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Flexible Pavement Performance
xxttx
Wp 4.2 4.2 1.5
xt t x xW p , , f
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AASHTO LEF
18 18 18
, ,, ,
x
t ts
x t t x x
W f pNLEFN W f p
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Flexible Pavement Performance
xxttx
Wp 4.2 4.2 1.5
x
xtt
x
W4.2 p4.2 1.5
x
t
tt
G
10 x 10x
W4.2 plog log4.2 1.5
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Pavement Performance
xtt x 10
x
WG log
10 10log log xt t xx
G W
10 10log log x tt xx
GW
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Pavement Performance
10 10log log x tt xx
GW
1010loglog10 10
txtx xG
W
10t
x
x
G
t xW
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AASHTO LEF
1818 1818 1810 10
10
t
t t
x
txx
GG G
tG
t xx
WLEF
W
xLEF e EALF
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AASHTO LEF
18
1818
log log log
xt t tx
t x
W G GW
1: log xx
NOTE this is not ee
This is the equation in the textbook
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Rigid Pavement Performance
xxttx
Wp 1.54.5 4.5
5.20
8.46 3.52
22
3.6311
.0 x
x LDL L
7.352
5.85 3.28
62
4. 210 1 x x
LL LD
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Rigid Pavement Performance
xxttx
Wp 1.54.5 4.5
x
xtt
x
Wp1
4.54.5 .5
t
xtt10
G
x 10x
Wplog log1.
4.54. 55
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TRUCK LOAD FACTORS
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Equivalent Single Axle Loads
12,000 32,000 32,000
ESAL = ??
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AASHTO Equivalency Factors
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Axle Load Histogram
0
50
100
150
200
250
6000-11999
12000-17999
18000-23999
24000-29999
30000-31999
32000-33999
34000-35999
36000-37999
38000-39999
40000-41999
Tandem Axle Load (lbs)
F
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q
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Single AxlesLoad Group
(lbs)Axle Count
per 1000 trucks LEF ESALs3000-6999 557 0.005 2.79
7000-7999 140 0.027 3.78
8000-11999 493 0.088 43.38
12000-15999 154 0.360 55.44
16000-17999 75 0.796 59.70
18000-19999 33 1.24 40.9
20000-21999 5 1.83 9.15
22000-23999 2 2.58 5.16
24000-25999 1 3.53 3.53
26000-29999 1 5.39 5.39
TOTAL = 229.2
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Tandem AxlesLoad Group
(kips)Axle Count
per 1000 trucks LEF ESALs6000-11999 227 0.010 2.3
12000-17999 162 0.037 6.0
18000-23999 108 0.150 16.2
24000-29999 140 0.429 60.1
30000-31999 58 0.757 43.9
32000-33999 25 0.97 24.3
34000-35999 6 1.23 7.4
36000-37999 3 1.54 4.6
38000-39999 1 1.89 1.9
40000-41999 1 2.29 2.3
TOTAL = 169.0
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Average Truck Load Factor
229 169 0.401000 f ESALsT Vehicles
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FHWA Truck Classes
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FHWA Class 4
Source: WSDOT Pavement Guide Interactive CD-ROM
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FHWA Class 5
Source: WSDOT Pavement Guide Interactive CD-ROM
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FHWA Class 6
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FHWA Class 7
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FHWA Class 8
Source: WSDOT Pavement Guide Interactive CD-ROM
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FHWA Class 9
Source: images.encarta.msn.com
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FHWA Class 10
Source: WSDOT Pavement Guide Interactive CD-ROM
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FHWA Truck ClassesClass Type EALF1 Motorcycles negligible2 Passenger Cars negligible3 Other Two-Axle, Four-Tire Single Unit Vehicles negligible4 Buses 0.575 Two-Axle, Six-Tire, Single Unit Trucks 0.266 Three-Axle Single Unit Trucks 0.427 Four or More Axle Single Unit Trucks 0.428 Four or Less Axle Single Trailer Trucks 0.309 Five-Axle Single Trailer Trucks 1.2010 Six or More Axle Single Trailer Trucks 0.9311 Five or Less Axle Multi-Trailer Trucks 0.8212 Six-Axle Multi-Trailer Trucks 1.0613 Seven or More Axle Multi-Trailer Trucks 1.39
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Typical Traffic Data
Source: WSDOT Pavement Guide Interactive CD-ROM
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WSDOT Simplified System
WSDOT Category FHWA Classes Assumed EALF
Single Units 4, 5, 6, 7 0.40
Double Units 8, 9, 10 1.00
Trains 11, 12, 13 1.75
Daily ESALs = 0.40(single units) + 1.00(double units) + 1.75(trains)
Source: WSDOT Pavement Guide Interactive CD-ROM
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TDOT Simplified System
VehicleType
FHWAClass
FlexibleEALF
RigidEALF
Cars & Motorcycles 1, 2 0.001 0.001
Pickups, Panel Vans 3 0.004 0.005
Buses 4 0.300 0.300
2-axle, 6-tire Singles 5 0.170 0.170
3-axle or more Singles 6, 7 0.700 1.000
4-axle Combos 8 0.700 0.780
5-axle or more Combos 9 -11 1.100 1.780
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Design ESALS
fESAL 365 ADT T T D L GTruck Load
Factor
LaneDistribution
Factor
DirectionDistribution
Factor
GrowthFactor
PercentTrucks
AverageDaily Traffic(two-way)
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Design ESALS
fESAL 365 ADT T T D L GTruck Load
Factor
LaneDistribution
Factor
DirectionDistribution
Factor
GrowthFactor
AverageDaily Truck
Traffic
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Design ESALS
m m m mi 1
ESAL 365 L D N T G
DirectionDistribution
Factor
DailyTruck Count(two-way)
GrowthFactor
TruckLoad
Factor
LaneDistribution
Factor
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Traffic GrowthCOMPARISON OF GROWTH IN VOLUME AND
LOADINGS ON THE INTERSTATE SYSTEM
70 72 74 76 78 80 82 84 86 88 90 92 94 96 98 00 020
100
200
300
400
500
600
700
P
E
R
C
E
N
T
G
R
O
W
T
H
(
3
-
Y
E
A
R
M
O
V
I
N
G
A
V
E
R
A
G
E
)
RURALAVERAGE DAILYLOAD
RURALAVERAGE DAILYTRAFFIC
YEARSource: Truck Weight Study and HPMS
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Growth Factor
1 1G 0 ng for gg
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Lane Distribution FactorsNumber of Lanesin Each Direction
Percent of Loadsin Design Lane
1 100
2 80-100
3 60-80
4 50-75