Three-Dimensional Finite Element Analysis of a Slab on Stress Dependent Elastic Solid Foundation

摘要

This report examined current computerized analysis techniques for slabs on grade. The focus of investigations presented is the application of the three dimensional finite element program GEOSYS for the analysis of a slab, resting on a stress dependent elastic solid foundation. This model can be used to establish baseline structural response data, representative of complex boundary and support conditions, thereby validating conclusions reached on the basis of two dimensional analysis. Many computer runs were conducted to develop user guidelines for the fruitful utilization of the three dimensional approach. Effects considered include mesh fineness and gradation, subgrade extent, boundary conditions, etc. The three fundamental loading conditions, viz. interior, edge and corner, are examined. Two typical single and multi-wheel U.S. Air Force aircraft are employed (F-15 and C-141). An iterative scheme is introduced to account for subgrade stress dependence. The effect of stress softening, typical of cohesive soils, is evaluated and discussed. A number of interesting observations are made, and their bearing on current analysis and design approaches is considered. Two broad areas for future research are identified. The relevance and need of the GEOSYS model to future pavement research/development activities is established. Keywords: Runway Pavements; Slab Model.