Rut Depth Measurement Method at FAA's National Airport Pavement Test Facility
This study discusses the rut depth measurement method used at the FAA's National Airport Pavement Test Facility. It covers how test conditions, loading conditions, data collections, transverse profiler usage, data processing, and profile processing software contribute to the evaluation and analysis of pavement conditions.
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Rut Depth Measurement Method at the FAA s National Airport Pavement Test Facility (NAPTF) Injun Song, Ph.D., P.E. SRA International, Inc. Gordon Hayhoe, Ph.D. FAA William J. Hughes Technical Center Transportation Systems Workshop 2012 5 8 March 2012 Renaissance Austin Hotel, Austin, Texas
Test Conditions Data from High Tire Pressure (HTP) Test items were used as an example test pavement. The 5-inch HMA pavement with PG 64-22 and PG 76-22 were tested. Wheel loads were 52,500 lbs (23.8 MT) and 61,300 lbs (27.8 MT). The loads were applied at a trafficking speed of 1 ft/s (0.305 m/s). The -7, 0, +7 inches wander patterns were used.
Loading Conditions CL 254 psi 218 psi North South 1.37 m (=54.00 ) 185 205 225 242.5 (73.9m) 260 280 300 Station: (56.3m) (62.4m) (68.5m) (79.2m) (85.3m) (91.4m) CL 195 215 232 253 270 290 PG 76-22 [61.3k] -Unheated- PG 76-22 [61.3k] -Heated- PG 76-22 [52.5k] -Heated- PG 64-22 [52.5k] -Heated- PG 64-22 [61.3k] -Heated- PG 64-22 [61.3k] -Unheated- 57.5 feet (17.5m) 57.5 feet (17.5m)
Data Collections Transverse profiles were measured during trafficking at the middle of each test item, 20 feet (6.09 m) apart. 66 feet (20 m) long truss profiler equipped with a non- contact vertical displacement transducer were used. The supporting points are capable of maintaining the same vertical reference points for the transverse profiles with pavement surface condition changes.
Transverse Profiler Encoder (DMI) Infrared Laser
Data Processing The collected profile data is processed using FAA developed processing software. Reference profile lines were taken at a designated calibration section without any loading applications. The straightedge simulation is performed on each profile line to compute the amount of maximum depression and upheavals in the pavement items. Any specific section of the profiles were cut and rotated for geometric comparisons.
Profile Processing Software EXAMPLE
Calibration of Beam Curvature Steel Aluminum Laser Ground
Calibration of Beam Curvature ??= ?? ? is thermal expansion coefficient and approximately 7.3*10-6 in/in F and 12.3*10-6 in/in F for steel and aluminum respectively. ??,n xi,n where ??,n is (processed) reference profile data at pass number ?, x?,n is profile data at pass number ?, and ? is profile data sequences from 1st to ?? data.
Cut and Rotate EXAMPLE
Cut and Rotate The sectioned profiles for target pavement area were first shifted vertically and rotated to make both start and end elevations equal at zero. A vector rotation can be conducted in terms of a typical linear transform matrix. A = cos sin cos sin Matrix A rotates each vector by an angle in the clockwise direction cos sin sin A = cos Matrix A rotates each vector by an angle in the counterclockwise direction
Straightedge Simulation EXAMPLE
Rut Depth Measurements (254 psi) (218 psi) 735 passes 840 passes
Thank You! Injun Song SRA International, Inc. Email: injun_song@sra.com Gordon Hayhoe FAA William J. Hughes Technical Center Email: gordon.hayhoe@faa.gov
