STRUCTURAL ANALYSIS OF BITUMINOUS CONCRETE PAVEMENTS R. C. Deen, H. F. Southgate, and J. H. Havens, Kentucky Department of Highways •RATIONAL criteria for the structural analysis of pavements are emerging from classical theories equated to the observed behavior of real pavements. Pavement be - havior is known to be affected by traffic , variations in soil support, and variations of component thicknesses and qualities. Considerable attention has been devoted to the mechanistic response of pavements to static and dynamic loads and to the development of theoretical analysis procedures that rely, in part, on the com putation of certain critical stresses, strains, and deflections in the structure. A compu ter program (1) that permits the analysis of elastic multilayered pavement systems has made possible the extensive investigation of the effects of soil support properties, strength character- istics of the materials used in the pavement structure, and component thicknesses. In this study, the computer program was used to determine the patterns of stresses, strains, and deflections of the pavement system. The study also attempts to show the relation between these stresses , strains, and deflections and current and proposed design curves by using the fatigue concept [equivalent axle loads (EAL's)J. From the mechanistic point of view, load-deflection relations outwardly portray the composite stiffness or rigidity of pavement systems. Contrary to general impressions, surface deflection is not a discrete, limiting parameter. Stresses and strains in the subgrade soil and in the extreme fibers of the bituminous concrete layers may con- stitute overriding, fundamental limits. Therefore, thickness design criteria cannot be based directly on deflection spectra. In other words, two different pavements having equ al, 18 - kip de fl e cti ons a re not necess ar ily e qual des igns unless all accompanying stresses and strains are also equal. COMPUTATIONS BASED ON THE ELASTIC THEORY The Chevron Research Company furnished a "privileged" duplicate of its computer program for the el astic analysi s of an n- laye red paveme nt sys t em to the Kentucky De- partment of Highways, Division of Research . This program is capable of handling the analysis of a 15-l ayere d sy stem and com putes for any specified depth an d distanc e fr om the axis of loading the stresses, strains, and deflec tion s. In d evel opi ng the Chevron program to make these computations, Michelow (!_ ) assumed the following : 1. The asphalt pavement is a semi-infinite solid of n layers; 2. The elastic characteristics of one layer can be different from those of another; 3. The component layers are homogeneous and isotropic and are characterized by Young's modulus and Poisson's ratio; 4. A uniformly distributed load on a circular area is placed on and "normal" to the free surface of the pavement; 5. The interfaces between layers are rough , i.e ., strains at the interface of two layers are identical; and 6. The bottom layer is a semi-infinite solid. The determination of stresses, strains, and deflections by using the Chevron program requires the input of the elastic characteristics of the materials contained in the various layers of the pavement system. Values for the moduli of the subgrade E3 investigated Sponsored by Committee on Flexible Pavement Design. 22
STRUCTURAL ANALYSIS OF BITUMINOUS CONCRETE PAVEMENTS
Jun 28, 2023
Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Related Documents
