Engineers have traditionally used strain calculations to estimate structural thickness design and life cycle performance of flexible pavements. The two primary strain calculations used for flexible pavement engineering are peak tensile horizontal orthogonal strain at the bottom of the hot mix and vertical compressive orthogonal strain at top of subgrade. These orthogonal strains have been assumed to correlate to primary pavement failure modes of fatigue cracking and rutting, respectively.
The objective of this study was to compare the orthogonal and shear strain response due to large vehicle loading of typical pavement structures and compare the strain response to traditional individual lane loading scenarios.
This study employed non-linear 3-D numerical modeling to evaluate two pavement structures, three truck configurations under multi-truck/multi-lane loading scenarios.Trucks evaluated in this study included typical Canadian 2-axle straight truck, 5-axle semi-truck, and 8-axle b-train. All trucks were modeled at maximum allowable legal load limits for Saskatchewan. The analysis was applied to relatively thick (primary) and thin (secondary) pavement structures in assumed summer field state conditions.
Based on the analysis conducted, this study found that multi-lane/multi-truck loading can significantly increase both peak strain and volumetric strain state response of a pavement structure. This study also found shear strain to be more sensitive to multi-truck/multi-lane pavement loading compared to orthogonal strains. Based on the findings of this study, multi-truck/multi-lane field state conditions should be considered when evaluating critical state analysis of heavily loaded multi-lane pavement facilities for improved structural design life cycle pavement performance predictions.
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