Difference between Pavement Thickness Design and Pavement Life Prediction for Rigid Aircraft Pavements

Greg White

doi:10.3390/designs6010012

Abstract

Aircraft pavements are generally designed using deterministic methods and using conservatively selected input parameter values, which combine to result in a low probability of structural failure occurring during the structural design life of the pavement. In contrast, when predicting the actual time until an as-constructed pavement will reach a structural failure condition, stochastic methods are required to take into account the inherently variable nature of pavement material properties and layer thicknesses, and the best-estimate of the input parameter values must replace the conservative values that are commonly used to introduce design reliability. A case study on a rigid aircraft pavement demonstrates the difference between pavement thickness design and pavement life prediction. Using Monte Carlo simulation, it was found that 98.5% of the as-constructed pavement was stronger than the designed pavement and that the predicted fatigue life of the pavement was approximately 180 times greater than the effective design life. It was concluded that the significant difference between pavement design and pavement life prediction explains the practical observation that rigid aircraft pavement service life generally exceeds typical structural design lives.

Highlights

Aircraft pavements are generally designed using conservative methods that result in a low risk of structural failure occurring during the design life of the pavement [1]
The structural failure of aircraft pavements is the basis on which pavement thickness design calculations are performed, and for rigid aircraft pavements, the only form of structural failure considered in thickness design is concrete slab fatigue cracking [5]
To predict the time until a pavement will reach failure, the failure condition must be understood, the chance of reaching failure implied by the design method must be defined, and a best estimate of the as-constructed pavement material properties and thicknesses must be considered

Summary

Introduction

Aircraft pavements are generally designed using conservative methods that result in a low risk of structural failure occurring during the design life of the pavement [1]. The structural failure of aircraft pavements is the basis on which pavement thickness design calculations are performed, and for rigid aircraft pavements, the only form of structural failure considered in thickness design is concrete slab fatigue cracking [5]. Because rigid aircraft pavements are designed conservatively and remain serviceable for many years beyond their structural design life, it follows that the fatigue failure of rigid aircraft pavements usually occurs much later than implied by aircraft pavement thickness design processes. Determining curling (upward and downward) stresses is difficult, and pavement thickness design does not directly account for these environmental loads

Objectives

Methods

Results

Conclusion