FEAFAA Software Update - Asociación Latino … Software Update.pdf · 2010-02-11 · FEAFAA...

Presented to: VI ALACPA Airport Pavements Seminar & IV FAA Workshop

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

Date: 29 October, 2009

Federal AviationAdministrationFEAFAA Software

Update

2Federal AviationAdministration

FEAFAA Software UpdateOctober 29, 2009

FEAFAA - Introduction

FINITEELEMENTANALYSIS -FEDERALAVIATIONADMINISTRATION

• Developed by the FAA Airport Technology R&D Branch

• Stand-alone tool for 3D finite element analysis of multiple-slab rigid airport pavements and overlays.

• Use FEAFAA to compute accurate responses of rigid pavement structures to individual aircraft landing gear loads.

• FEAFAA is not intended as a design procedure.



Acknowledgments

• SRA International Corp.– Dr. Izydor Kawa– Dr. Qiang Wang



FEAFAA – Major Features

• 9-slab jointed rigid pavement model

• Up to 6 structural layers• Infinite subgrade model• Arbitrary gear loading

capability• Overlay modeling capability• User-defined slab size• Customizable aircraft library



FEAFAA – Major Revisions (ver. 1.42)

• Pavement Mesh Model– The gear can now be

repositioned anywhere on the surface.

– Uniform 3D mesh.– User-variable mesh size. – Improved mesh boundary

constraints prevent “spurious” stresses from being induced at the slab corners.

“Old” Model with spurious stresses



FEAFAA – Major Revisions (ver. 1.42)

• Windows Interface– The internal airplane library has

been updated.– The 2D Shell model for slabs is

no longer supported.– Controls allow the user to define

the position of the gear using an x,y coordinate system and a variable gear angle.

– The x-offset is now given relative to the coordinate origin at the edge of the slab (same as mesh coordinate system).

– Interior Load/Edge Load option.



NIKE3D Finite Element Processor

• FEAFAA drives a modified version of the 3D finite element program NIKE3D, originally developed by the U.S. Department of Energy, Lawrence Livermore National Laboratory (LLNL).– Same program used in FAARFIELD.– The FAA-modified NIKE3D and INGRID mesh

generation programs are distributed in compiled forms under a software sharing agreement between the FAA and LLNL.



NIKE3D Recent Changes

• Recompiled the NIKE3D processor to remove the size limitation on the output file.

• Corrected an error in the infinite element formulation.

• Improved the contact surface algorithm.– This results in a better solution for cases where

slab/base separation is likely to occur (e.g., on the unloaded side of a joint.).



FEAFAA 3D Rigid Pavement Mesh

9 Slabs

Up to 6 structural layers

Infinite ElementsMathematically represent a subgrade of infinite depth

Sliding Interface



Running FEAFAA –1. Airplane Selection Window



Running FEAFAA –2. Pavement Structure Window

Edge Load (Longitudinal




Edge Load (Transverse)




Interior Load




Skew Load



Running FEAFAA –3. Joint Modeling Window



Running FEAFAA –4. 3D Mesh Generation Window

Generates NIKE3D Input File



Running FEAFAA –4. 3D Mesh Generation Window

Executes NIKE3D Session



Running FEAFAA –5. NIKE3D Execution Window

• Execution time depends on the problem – 20-30 minutes is typical.

• DOS window will continue to display execution progress.– Session information (screen

display) is written to a file called Nike3d.txt.

– Solution is written to a file called n3dhsp.



Analyzing FEAFAA Results

• FEAFAA does not include a visual post-processing capability.

• Finite element results can be viewed using commercially available software, e.g., TecPlot or MatLab.

• FEAFAA includes a utility program, NikePlot, that converts the output file to a simple text format readable by TecPlot.



NikePlot Utility

• Make sure output file n3dhsp is in the same directory as NikePlot1-5.exe.

• Run NikePlot1-5.exe.• Enter the vertical scale

factor when prompted.• NikePlot generates 2

text files:– model_load.dat– model_stress_1.dat



FEAFAA Example

• Airplane Gear Load– B777-200 Baseline

(6 wheels)– Gross Weight

= 537,000 lbs.– Tire Pressure = 185 psi– Rectangular tire footprint

(PCA)– Gear position:

Longitudinal joint along inside tire edge.

• Pavement Structure– Slab size 20 × 18.75 feet– 14 in. PCC Overlay

• E = 4,000,000 psi– 12 in. Existing PCC

• E = 4,000,000 psi– 8 in. Subbase

• E = 250,000 psi– Subgrade, E = 8,000 psi– No symmetry– Joint: 1.25 in. diameter

dowels @ 15 in. spacing



FEAFAA Example – Airplane Selection



FEAFAA Example – Pavement Structure



FEAFAA Example – Joint Modeling



FEAFAA Example – 3D Mesh



FEAFAA Stress ResultsPlotted Using NikePlot Utility and and TecPlotTM

Stress-z Stress-x

Stress-yDetail of Stress-y

Overlay

Base PCC

Compression

Tension

Longitudinal Joint



FEAFAA Example - Statistics

• Number of Finite Elements = 18,781• Number of Equations = 84,540• Number of Iterations = 32• Total Run Time Charged = 43.07 minutes*

*Intel® Pentium 4® Processor, 3 GHz, 2 MB RAM



Where to Obtain

• Download FEAFAA from:http://www.airporttech.tc.faa.gov/naptf/download/

• Current version: FEAFAA 1.401• Check back for new updates• More Information: [email protected]



Current Limitations• Rigid pavement analysis only.• No metric option at this time.• Restricted to 9 slabs.

– Overlay joints must coincide with base slabs. – Joint stiffness is variable, but all joints must have the

same stiffness.

• Gear loading only.– Future versions will introduce combined temperature

and wheel loads.

• FAA is continuing to add improvements.

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FEAFAA Software Update - Asociación Latino … Software Update.pdf · 2010-02-11 · FEAFAA...

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