Pavement Modeling and Design

Implementation of Rigid Pavement Thickness Design - New Pavement

LEDFAA is a computer program which is based on layered elastic analysis (LEA) and fullscale test data. It has been a part of the U.S. Federal Aviation Administration’s (FAA) Advisory Circular AC 150/5320-16 since 1995. However, one of the limitations of LEDFAA for rigid pavements is the lack of a direct slab edge stress calculation. Slab interior stress is calculated first, then converted into edge stress using transformation functions developed for specific aircraft. The FAA has been working on replacing the indirect slab edge stress calculation in LEDFAA with a direct slab edge stress calculation using a three-dimensional finite element method (3D-FEM). Requirements of the new procedure are that it run on any personal computer, be user-friendly, and be applicable to any gear configuration. The FAA plans to produce a 3DFEM based design procedure as a new design standard for release in FY 2006. A finite element model of the pavement structure was developed and run with a general-purpose 3D-FEM program (NIKE3D) available in the public domain. NIKE3D and its associated preprocessor program INGRID were originally developed by the Lawrence Livermore National Laboratory, USA. Both programs have been recompiled as dynamic-link libraries and incorporated into LEDFAA. Currently, the project has moved to the stage of implementation of the new modified design procedures incorporating the 3D-FEM model. This paper presents the structure of the new FAA program for pavement thickness design. Example results from the program are presented and compared with results from the existing FAA design procedures.

Authors: Izydor Kawa, Edward H. Guo, Gordon F. Hayhoe, David R. Brill