Pavement Design and Evaluation

RPA P5

REDAC Subcommittee on Airports

David R. Brill, P.E., Ph.D.

August 17, 2016

Presented to:

By:

Date:

Federal Aviation

Administration

Federal Aviation

Administration

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RPA P5 – Pavement Design and Evaluation

Need

There is a need for advanced, computer-based pavement design & evaluation solutions to protect the FAA’s investment in airport pavement. The FAARFIELD program provides confidence that pavements will meet the required service life. Savings to the AIP will result from reduced construction costs and fewer runway closures.

Research Goals

Continue to update and modernize the FAARFIELD design software.

New ACN-PCN system of reporting airport pavement strength by FY17.

Incorporate top-down cracking mode in FAARFIELD rigid design by FY18.

Fully integrate FAARFIELD thickness design with LCCA procedures by FY22.

August 17, 2016

2

FY 2016 Accomplishments

Release FAARFIELD v. 1.4.

New FAARFIELD-based ACN-PCN method for evaluation.

Tech Note on improved treatment of aircraft gears in tandem.

Funding Requirements
| Project                            | Contract Funds ($K) |         |         |
|------------------------------------|---------------------|---------|---------|
|                                    | FY 2016             | FY 2017 | FY 2018 |
| P5. Pavement Design and Evaluation | 2090                | 1200    | 1236    |
| P5.1. Design Improvements          | 875                 | 750     | 771     |
| P5.2. ACN-PCN Improvements         | 250                 | 250     | 250     |
| P5.3. Analysis                     | 965                 | 200     | 215     |

Pavement Design & Evaluation

Federal Aviation

Administration

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Draft AC 150/5320-6F

August 17, 2016

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Posted 1 June 2016 for comment: http://www.faa.gov/airports/resources/draft_advisory_circulars/

Includes FAARFIELD 1.4

Federal Aviation

Administration

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FAARFIELD 1.4 – Release Version

August 17, 2016

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Federal Aviation

Administration

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FAARFIELD 1.4 – What’s New?

Completely revised flexible and rigid failure models based on current NAPTF full-scale test data.

Reduced excess stabilized base thickness requirement.

Improved, more accurate 3D finite element model.

Completely rewritten concrete overlay design procedure.

Automatically generates PDF design report.

Automated, software-based compaction criteria.

Updated aircraft library aligned with COMFAA 3.0.

Include non-airplane vehicles in library (ARFF vehicles, etc.)

Support for user-defined gear configurations.

Advanced, energy-based asphalt fatigue models.

All data files now stored in document directories.

August 17, 2016

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Federal Aviation

Administration

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Improved 3D Finite Element Mesh

August 17, 2016

Pavement Design & Evaluation

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FAARFIELD 1.41

FAARFIELD 1.305

More accurate stress results.

Improved infinite foundation model.

Still one slab model with assumed 25% load transfer.

Federal Aviation

Administration

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Rigid Pavements

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Effect of Concrete Flex Strength

Effect of Traffic

New thickness designs are generally less conservative than FAARFIELD 1.3 designs for the same inputs.

Sensitivity to factors such as concrete strength, traffic level and subgrade support is similar to FAARFIELD 1.3.

19 November 2015

FAARFIELD 1.4 Intro & Updates

Federal Aviation

Administration

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Flexible Pavements

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Conventional Flexible Pavement Comparison

Stabilized Flexible Pavement Comparison

New thickness designs are generally less conservative than FAARFIELD 1.305 designs for the same inputs.

Reduced stabilized base thickness requirements on P-209 subbase.

19 November 2015

FAARFIELD 1.4 Intro & Updates

Federal Aviation

Administration

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Automated Compaction Criteria

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Computes compaction control points for rigid & flexible pavements.

August 17, 2016

Pavement Design & Evaluation

Federal Aviation

Administration

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Direct Evaluation of Tandem Gear Damage(Flexible)

Old method was a two-part pass/coverage (P/C) ratio consisting of a wander-related factor multiplied by a tandem factor.

New method: Compute CDF for multiple wheels in tandem by numerical integration of the longitudinal strain profile.

Similar to method used by French DGAC (Alizé).

Displayed P/C ratio now relates only to wander. 

August 17, 2016

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Old Method

New Method

Federal Aviation

Administration

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Report in Publication

Technical Report “Replacement of FAARFIELD Tandem Factors with CDF Methodology”

Documents changes to evaluation of tandem gear damage.

In final editing.

August 17, 2016

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Federal Aviation

Administration

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Legacy Fortran Libraries

Existing Fortran libraries are modified from original 1995 programs.

Still distributed by FAA under a software sharing agreement with Lawrence Livermore National Laboratory, the original NIKE3D developer.

Very significant limitations for .NET programming.

Unmanaged code.

Not under the control of .NET memory management services.

May lead to memory conflicts or crashes at runtime. 

Obsolete data storage and retrieval methods.

Few young programmers have knowledge of Fortran.

August 17, 2016

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Federal Aviation

Administration

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FAARFIELD Calling Structure

August 17, 2016

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Federal Aviation

Administration

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Short-Term Improvement

Enforce data type consistency.

Legacy program uses a single common array to store dissimilar data types.

Replace with multiple common arrays targeted to specific data types.

Better error handling.

Recompile existing Fortran libraries to fixed memory space.

August 17, 2016

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Improvement to NIKE3D Common Storage Arrays (in progress)

Federal Aviation

Administration

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Long-Term Solution

The FAA needs modern replacements for its legacy finite element libraries Ingrid.dll and Nike3d.dll. 

Similar to LEAF, the new libraries should be:

Open-source.

Freely distributable – could be shared with third parties.

Compatible with modern computing systems.

Keep the functionality of current NIKE3D.

Retain only element types, material libraries, etc., that are needed for design and analysis of pavements.

In progress: VB.NET replacement for Ingrid.dll.

August 17, 2016

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Federal Aviation

Administration

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Further Improvements

Modernize the FAARFIELD graphical user interface (GUI).

Job and section entry.

Improved start-up screen.

Improved screen re-sizing and appearance.

Improved flow between screens.

Rationalize data file structure.

August 17, 2016

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Federal Aviation

Administration

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Top-Down Cracking Mode (Rigid)

Current efforts are focused on artificial neural networks (ANN) for multi-slab model with curling.

Fast, accurate solutions within the defined problem space.

Grant to Iowa State U.

P.I. Dr. Halil Ceylan

1st year of 3-year project.

August 17, 2016

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ANN Development: Input Parameters

Federal Aviation

Administration

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Questions?

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August 17, 2016

Pavement Design & Evaluation

Federal Aviation

Administration

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