Three‐Dimensional Finite Element Analysis in Airport Pavement Design

Abstract

This paper discusses work being performed at the Federal Aviation Administration (FAA) Airport Technology R&D Branch in the development of a three‐dimensional finite element‐based airport pavement design procedure for rigid airport pavements. The structure of the pavement design procedure and the function of the finite element structural model within it are described. A major focus of current FAA research and development efforts is on reducing run time. A simplified, single‐slab mesh runs on a personal computer and returns a maximum edge stress in a fraction of the time required by the full nine‐slab mesh. Results are presented for the simplified mesh for various aircraft types and slab sizes and compared to the larger mesh. Two types of foundation models are considered to represent a subgrade of infinite depth. A subgrade model consisting of discrete springs at nodal points approximates the distributed spring (Winkler) foundation with subgrade modulus k used in Westergaard analysis. An alternative model makes use of infinite elements to represent a linear elastic foundation with elastic modulus E and Poisson’s ratio μ. Stress computations using both models show that the Winkler foundation model is significantly more sensitive to slab size than the infinite element model for dual‐tridem (six‐wheel) aircraft gear loads. In a recent project at the FAA Center of Excellence (COE) for Airport Pavement Research, the open source code software (Nike3D) used in the three‐dimensional finite element computations to include the infinite element formulation. The infinite element was implemented as a new material type applicable to standard eight‐node elements in the Nike3D element library.