The Federal Aviation Administration (FAA) has introduced the first major changes to its FAARFIELD standard pavement design software since the last version was released in 2010. These program upgrades accompanied a thorough revision of Advisory Circular (AC) 150/5320-6 covering airport pavement design and evaluation. The newly released program, designated FAARFIELD 1.4, includes significant modifications to both rigid pavement and flexible pavement design models, and adds new features to improve the user experience. This paper summarizes the principal technical changes to structural models, failure models and design logic that affect thickness design using FAARFIELD. It is shown by examples that designs performed using FAARFIELD 1.4 typically are less conservative than in the previous version (FAARFIELD 1.3); however, exceptions to this general statement may be found. This paper also includes discussion of programming changes implemented in the FAARFIELD overlay design procedures that improve both speed and accuracy.

The Federal Aviation Administration (FAA) has recognized for some time that its current rigid pavement design model, involving a single slab loaded at one edge by a single aircraft gear, is inadequate with respect to top-down cracking. Thus, one of the major observed failure modes for rigid pavements is poorly accounted for in the FAA Rigid and Flexible Iterative Elastic Layer Design (FAARFIELD) design software. A research version of the FAARFIELD design software has been developed in which the single-slab three-dimensional finite-element (3D-FE) response model is replaced by a four-slab 3D-FE model with initial temperature curling to produce reasonable thickness designs accounting for top-down cracking behavior. However, the long and unpredictable run times associated with the four-slab model and curled slabs make routine design with this model impractical. Artificial intelligence (AI)-based alternatives such as artificial neural networks (ANNs) have great potential to produce accurate stress predictions in a fraction of the time. ANNs could be practical replacements for a full 3D-FE computation that requires long computation times. In the development of ANN models, both individual input parameters and dimensional analysis have been considered, and accuracy of predictions from both methods was compared. ANN models for only mechanical and simultaneous mechanical and thermal loading cases were developed using individual input parameters and dimensional analysis. It was observed that very high accuracies were achieved in predicting pavement responses for all cases investigated.

The Federal Aviation Administration initiated a runway instrumentation project in 1992 by installing 460 static and dynamic sensors in sixteen slabs in the take-off area of Runway 34R-16L at Denver International Airport. Static sensors such as embedded temperature and moisture gauges and dynamic sensors such as H-bar strain gauges, LVDTs, and position strain gauges were installed. The investigation was focused on measuring pavement response to aircraft loading and environmental conditions. Currently, the data collection system is severely damaged due to water infiltration and is not operational. Data was collected from 1995 through 1999 which included real-time pavement strains and deflections resulting from aircraft traffic. The slab strain and vertical deflection data was analyzed and compared to three-dimensional finite element model predictions. Overall, good agreement between measured and predicted strains and vertical deflections was observed. This information was used for, among other things, validating and calibrating the structural model in FAARFIELD. An important parameter missing in FAARFIELD is the effect of curling on pavement thickness design. Severe curling can cause premature cracking and incur high maintenance costs. The primary objective of this project is to restore the data collection system to at least measure slab deflections and strains. The future emphasis will be on characterizing slab curling under varying environmental conditions and incorporating it into FAARFIELD. Efforts are underway to restore the data collection system. The entire project is expected to be completed by September 2010. Once resurrected, the instrumentation project will provide valuable slab curling data for updating structural models in FAARFIELD. This paper describes in detail the restoration of the Denver International Airport instrumentation project and the ways in which the FAA plans to make use of the collected data.

Between 2014 and 2016 the Federal Aviation Administration (FAA) conducted full-scale traffic tests of flexible pavements at its National Airport Pavement Test Facility (NAPTF) at the William J. Hughes Technical Center, Atlantic City International Airport, NJ, U.S. The purpose of these tests, part of NAPTF Construction Cycle 7 (CC7), was to evaluate the International Civil Aviation Organization’s (ICAO) existing criteria for allowable occasional aircraft overloads on flexible airport pavements. ICAO Annex 14 currently limits such overloads to 10 percent above the published pavement classification number (PCN). The applied traffic consisted of the design gear loads alternating with increasing levels of overloads (2-wheel, 4-wheel, and 6-wheel) in a specific sequence. FAA tests confirmed that the ICAO criteria are highly conservative. While higher traffic loads led to earlier failures, overloads of up to 50% above PCN did not alter the parameters of the failure curve, suggesting that for overloads up to this magnitude, the cumulative damage factor (CDF)-based failure model can be used reliably to compute reduced life. However, very high overloads of 90–100% above PCN caused more rapid acceleration of the failure. The findings of this full-scale test will be used to support future revisions to the existing overload criteria.

In recent years, the Alaskan Region of the Federal Aviation Administration (FAA) reported performance issues with some flexible airport pavements. The issues were attributed to changes in the thermal regime of the permafrost layers resulting from a warming trend. The poor pavement performance was also caused by such factors as improper design and construction. The FAA Airport Technology Research and Development Branch selected three runways with an asphalt surface from three airports in Alaska and reviewed the pavement failures, design, and construction histories to determine the causes and contributing factors of flexible pavement performance issues. The goal was to determine if and where modifications to FAA guidance concerning design and construction in frost and permafrost zones were needed. This paper focuses on identifying frost and permafrost issues at the airports, identifying the design criteria used at the airports, and determining how closely the design criteria and construction practices followed FAA guidance. The work also recreates the pavement design for each runway, following FAA guidance in effect at the time of the design. Researchers identified areas of the FAA frost and permafrost design criteria that are silent or subject to conflicting interpretation. The paper provides recommendations for possible improvements to current FAA guidance with respect to frost and permafrost design, based on findings from the design reviews. The recommendations target Advisory Circulars 150/5320-6G and 150/5270-10H and are intended to address the design- and construction-related issues.