Traffic Loading and Volumes.pdf

8/9/2019 Traffic Loading and Volumes.pdf

1/31

CivE 542

Pavement Structural Design

Lecture 2: Traffic Loadingand Volume

El-Hakim


2/31

Lecture Outline

Traffic Data Challenge

Single Load Equivalency (Solution!)

AASHTO Road Test Relative Damage

Truck Factor

Variation of Truck Flows and Loads Load Equivalency Factors (LEF)

Equivalent Single Axle Load (ESAL)


3/31

Traffic Data

Regional Traffic Office

Commercial Vehicle Surveys

Transportation Planning Branch Weigh-In-Motion (WIM)

Vehicle Inspection Stations (Static Scales)


4/31

Challenge


5/31

Challenge


6/31

Challenge


7/31

Challenge

Traffic Data

Average Annual Daily Traffic (AADT)

Percentage of Commercial Vehicles

Truck Count Survey


8/31

Single Load Equivalency

Load Equivalency Factor

Standard Axle is 18 kip (18,000 lbs or 80.1 KN)

Damage caused by an X lbs axle is equivalent

to damage caused by LEF number of standard

axles (18,000 lbs)


9/31


Example

100,000 reps of 18 kip (Single Axle Loads)

14,347 reps of 30 kip load (Single Axle Loads)

Find LEF 30 kip SAL

LEF30-kip single = 100,000/14,347 = 6.97


10/31


Definition According to AASHTO

Number of Standard Axle Loads (80KN)

Number of a given axles load (e.g. 133

KN) required to cause a certain level ofdamage

LEF =

N80KN

N133KNLEF =


11/31

AASHTO Road Test

American Association of State Highway and

Transportation Officials


12/31

Relative Damage

Example

Whats the Relative Damage of 36 kip single

axle compared to 18 kip standard single axle?

LEF= (36/18)4= 16

Fourth Power Law Relative Damage = (Ratio between axle loads)4


13/31

Relative Damage

Single Axle Load (kip)

RelativeDamage


14/31

Truck Factor

Average amount of Damage done by one

vehicle

Expressed for various vehicle classes


15/31

Truck Factor


16/31

Truck Factor


17/31


18/31

Truck Factor


19/31


20/31

Variation of Truck Flows and

Loads Site specific estimates of truck loads are

better than mean Truck Factor estimates

Number of data collection sites are limited

by cost and available workforce


21/31

Load Equivalency Factors


22/31

Load Equivalency Factors

Fourth Power Law

LEF= Axle LoadStandard Load

4


23/31

LEF and ESAL

Load Equivalency Factor (LEF): Measure of

relative damage of an axle

Equivalent Single Axle Load (ESAL):

Measure of relative damage associated with

a truck

Design Application: Convert Trucks to

ESALS


24/31

Equivalent Single Axle Load

(ESAL)


25/31

Equivalent Single Axle Load

(ESAL)


26/31

ESALExample

Truck Classes

Load (lbs) 4 5 6

22,000 206 57 70

26,000 100 69 64

29,000 74 52 50

32,000 59 48 38

Single Axles

Truck Classes

Load (lbs) 4 5 6

22,000 163 74 65

26,000 156 52 57

29,000 120 47 48

32,000 93 45 36

Tandem Axles


27/31

ESAL

MTO Tables Refer to MTO report posted on

LEARN


28/31


29/31

ESAL (Approx)

ExampleAADT (Both Directions)=10,000 %Trucks = 12%4-lane road 90% trucks in Outer Lane (Design Lane)

ESAL per Truck = 3 ESALs Design period = 20 years

Trucks per day (one Direction) = 10,000 x 0.5 x 0.12 = 600

Trucks per day on Design Lane = 600 x 0.9 = 540

Cumulative Trucks on Design lane in Design Period = 540 x

365 x 20 = 3,942,000

Design ESAL per Design Period = 3,942,000 x 3 = 11.826 M

ESAL


30/31

Traffic DatabaseOntario - MTO

http://www.mto.gov.on.ca/iCorridor/
http://www.mto.gov.on.ca/iCorridor/http://www.mto.gov.on.ca/iCorridor/


31/31

Thank you

Questions

Documents

Traffic Loading and Volumes.pdf