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Introduction PSI (Present Serviceability Index) IRI (International Roughness Index) Correlations Between PSI and IRI Measurement Techniques Docsity.com 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. Docsity.com Flexible pavement PSI can be obtained by the equation (1): Rigid pavement PSI can be obtained by the equation (2): Docsity.com 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. Docsity.com RARS80 : 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 6 0 i n c h e s Docsity.com 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. Docsity.com Reported by Paterson in 1986 PSI = 5×e(-0.18×IRI) Al-Omari and Darter in 1992 PSR = 5×e(-0.0026×IRI) Hall and Munoz in 1999 PSI = 5－0.2397x4＋1.771x3－1.4045x2－1.5803x x = log(1＋SV) SV = 2.2704(IRI)2 However, since Holman’s equations database is much smaller, Al-Omari and Darter’s equation is more widely used. Docsity.com Profilographs: Widely used for rigid pavement construction inspection, quality control and acceptance These devices consist of bogie wheel sets at the front and rear, a recording wheel at the center and a strip chart recorder for capturing the movement of the recording wheel relative to the bogie wheels. Roughness is recorded by the strip chart The most common profilograph is the truss-type California profilograph. The profilograph is pushed along the pavement, and 3 to 5 kilometers of the pavement can be measured in 1 hour Docsity.com 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 Docsity.com 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 Docsity.com
