Contribution of dynamic vehicle loads to pavement failure

Abstract

Pavement surfaces are not ideally even, which causes dynamic loads of vehicle axles. Distribution of dynamic loads of a given axle is similar to normal distribution and can be described by static load and dynamic load coefficient. The dynamic load coefficient depends on road profile, vehicle speed, properties of suspensions and static load of axle. While for a given road section road profile remains constant, vehicle speed and suspension properties are subject to limited variations, the static loads of particular axle vary significantly. The weigh-in-motion systems are the source of data on static loads, which are characterized by axle load spectra. The axle load spectra are the key data input for pavement design. The article presents a new approach to inclusion of the dynamic loads in axle load spectra. The theoretical explanation is supported by sample calculations. A one-kilometer road section was selected for calculations and its profile was measured using laser road surface profilograph. The dynamic loads were then calculated using the quarter car model and parameters appropriate for heavy vehicle suspensions. This part of calculations proved that dynamic loads significantly increase for less loaded axles. Dynamic axle load spectra were calculated based on static axle load spectra and function of dynamic load coefficient. The load equivalency factors and truck factors were calculated using the fourth power equation and considering both static and dynamic axle load spectra. Contribution of dynamic loads to pavement failure equals up to 19% for the considered example of road profile, which is characterized by IRI = 1.54 m/km.