Closed-Form and Graphical Solutions for Three-Layered Concrete Pavements

Analysis and design of three-layered portland cement concrete pavement systems incorporating a base layer have long been hampered by the scarcity of theoretically sound closed-form approaches. This study is focused on verifying and extending the method of transformed sections (MTS), a closed-form approach derived in 1992 on the basis of dimensional analysis and engineering mechanics. The applicability of the MTS to dense liquid and elastic solid foundations is studied in detail using a wide range of numerical test data for all three fundamental loading conditions (interior, edge, and corner). Both unbonded and bonded interface conditions between the two man-made layers are considered. To make the analysis easier, the MTS is incorporated into computer program WESTERX, a compendium of closed-form solutions for two- and three-layered concrete pavements. Maximum responses (bending stresses, deflections, and subgrade stresses) predicted by plate theory MTS are compared with those obtained from the finite-element computer program ILSL2X. Formulas developed to apply a compressibility correction to these responses are verified using results obtained from layer-elastic analysis (computer program DIPLOMAT). Critical responses from plate theory MTS are presented in the form of dimensionless charts, which can be used as an alternative to the closed-form approach with either of the two subgrade idealizations for all three fundamental loading positions. Graphical solutions are also developed for maximum responses that account for the compressibility of the two man-made layers under interior loading conditions for both foundation types.