Effects on Flexible Highways of Increased Legal Vehicle Weights Using VESYS IIM.

摘要

This report provides results of a detailed study to estimate lifetime costs for flexible pavements as a function of legal axle limits using an improved version of FHWA Computer Program VESYS IIM. VESYS IIM was modified to include capabilities for: (1) seasonal characterizations of pavement materials, (2) a discretized representation of axle load distribution,and (3) low-temperature cracking predictions. A combined survey of the literature and laboratory testing program was conducted to define the variations in material permanent deformation parameters as important material characteristics vary seasonally with the environment. The resulting data and other information and experience were applied to arrive at input data that would yield realistic performance predictions. A factorial of 64solutions was obtained using the improved version of VESYS IIM and the input data developed to study the effects of truck traffic consistent with four levels of legal axle limits (18, 20, 22and 24 kips),two levels of traffic,two levels of pavement section thickness and four environmental zones (Wet-Freeze,Dry-Freeze,Wet-No Freeze and Dry-No Freeze). Where failures were predicted,an overlay was applied and a new solution obtained until a pavement life of at least 20years was attained. The initial and overlay costs were estimated and these costs for 20years of pavement service were related to the legal axle limits.