Present Serviceability Index - Pavement Managment System - Lecture Slides, Slides of Management Fundamentals

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 Introduction

 PSI (Present Serviceability Index)

 IRI (International Roughness Index)

 Correlations Between PSI and IRI

 Measurement Techniques

 Serviceability is the ability of a specific section of pavement to serve high-speed, high-volume, mixed traffic in its existing condition.

Road quality

and condition

PSI

IRI

 PSI is the foundation of pavement maintenance decision and road economic analysis. It is used to judge the condition of the road whether meet the traffic requirement.

 PSI (based on AASHO Road Test) is a mathematical combination of values obtained from certain physical measurements so formulated as to predict the PSR for those pavements within prescribed limits.

1. Since PSI is based on the AASHO Test data about 50 years ago, and the vehicles, road characteristics and traffic speeds have been improved a lot, the applicability is questionable.
2. PSI includes not only the rideability but also the surface defects. For the management of pavement inventory, it would be better to have separate measures of ride quality and surface defects.
3. People use more advanced instruments to measure roughness, but the PSI equations are based on the profilometer which is no longer used today, thus, there must be some errors using PSI equations.

 IRI is used to define a characteristic of the longitudinal profile of a traveled wheeltrack and constitutes a standardized roughness measurement. (m/km; mm/m)

 Rougness Experiment was held in Brasilia, Brazil, in 1982

 Sponsored by the World Bank

 RARS 80 :

reference average rectified slope @ 80 km/hr

 It is the ratio of the accumulated suspension motion of a Quarter-Car divided by the distance it traveled with a speed of 80 km/hr during the test.

1 mile

60 inches

Disadvantage:

 Measurement of IRI has the deviation to asphalt pavement and against concrete. This is because of the fact that most concrete pavements have sawed joints at regular intervals, and given a “rough” surface.

Advantages:

Better repeatability :

 Repeatability refers to the ability of one machine to get the same result on the same stretch of roadway in two different passes. Better reproducibility :  Reproducibility refers to the ability of two machines to get the same result on the same stretch of roadway.

 Profile Dipstick

A handle is mounted on the frame for walking

A microcomputer is fixed on the dipstick to record the data and computer the slope of the road

An inclinometer enclosed in a case which is supported by two legs separated by 12 in Docsity.com

 MERLIN Instrument: simple and low cost (Machine for Evaluating Roughness using Low-cost Instrumentation)

200 measurements (one record for each revolution of the instrument’s wheel) have to be made at regular intervals to determine roughness.

It is a 1.8m long metal structure, with a wheel in front, a fixed base at the rear and an oscillating central support. The latter measures the elevation of a point with respect to the grade line defined by the other two points.

 Advantages:

 1) The initial cost is low.

 2 ）The operation of profilograph is simple.

 3) It has good repeatability.

 Disadvantages:

 1) The speed of operating a profilograph is low.

 2) It is unable to measure roughness at wavelengths equal to integer multiples of the wheel base.

Profilograph Output

 Inertial Profilometers

 The principal components: the height sensor(s), accelerometer(s), a distance measuring system, and computer software and hardware.

 Most common height sensors: Laser sensors