A comparative assessment of mechanistic load equivalence factors for flexible pavements

Oancea, Marius-Adrian (1991) A comparative assessment of mechanistic load equivalence factors for flexible pavements. Masters thesis, Memorial University of Newfoundland.

[English] PDF (Migrated (PDF/A Conversion) from original format: (application/pdf)) - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (23MB) [English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. (Original Version)

Abstract

This study deals with mechanistic Load Equivalence Factors (LEF) for flexible pavements. It addresses two sets of objectives. First, a theoretical investigation of cycle counting methodologies used for mechanistic LEF's calculation was carried out. Second, a number of these methods were used for calculating LEF's from in-situ strains. -- The study includes an extensive literature review, starting with the empirical approach proposed by the AASHO Road Test (AASH0, 1961). Mechanistic methods for LEF's calculation are subsequently introduced and discussed. -- Next, the concept of fatigue cycle, as defined by the ASTM standard E 1049-85, is introduced and its applicability to flexible pavements is investigated. As a result of the comparison of all the fatigue cycle counting methods proposed by the standard, the Range-Pair Counting Method was selected for LEF's calculation. -- The experiment undertaken in order to obtain strain versus time histories included two experimental trucks, namely a 3-axle configuration and a 5-axle configuration. The experiment involved 3 levels of speed, 3 levels of loading and 2 replicate runs of the experimental vehicles for each speed and load combination. Each set of 2 replicate runs of the experimental trucks were followed by an equal speed run of the Benkelman Beam truck. -- Resulting strain versus time histories were evaluated in terms of the quality of the lateral placement. Those corresponding to the best lateral placements were processed by the proposed ASTM Range-Pair Cycle Counting method, by the mechanistic method employed during the RTAC 1986 study, and the results were compared to the empirical AASHO LEF's. A new integral approach, based on the cycle definition provided by the selected ASTM method for cycle counting, was also introduced. -- Comparative assessment of LEF's calculated by different methods was made in order to validate numerically and investigate the suitability of each method for LEF's calculation.

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