Research described in this paper constitutes the final stage of a multicomponent project, which examined current computerized analysis techniques for slabs on grade. For a more realistic representation of a pavement system, an existing three-dimensional finite elementprogram (geosys) was modified. This can be used to analyze flexibleor rigid pavements, thereby validating conclusions reached on the basis of conventional two-dimensional analysis. In the first part of this study, many runs were conducted to develop user guidelines for the fruitful utilization of the geosys model. Effects considered included, among others, mesh fineness, vertical and lateral subgrade extent, boundary conditions, and stress extrapolation from computer results. Practical applications of the three-dimensional approach are presented in the second part of the paper. The three fundamental loading conditions, namely, the interior, edge, and corner of a slab resting on a stress-dependent, elastic, solid foundation are examined.Two typical single-wheel and multiwheel u.S. Air force aircraft (f-15 and c-141) are considered. An iterative scheme is introduced to account for subgrade stress dependence, and the effect of stress softening, typical of cohesive soils, is evaluated and discussed. Results from this program are compared to those from conventional two-dimensional analyses, employing finite element, finite difference, and numerical integration techniques. This paper appears in transportation research record no. 1196, Pavement evaluation and rehabilitation.
Abstract