Proposed Changes to the

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• Proposed Changes to the
• AASHTO PDDX-1 File Format
• Presented to the
• AASHTO Joint Technical Committee on Pavements
• Williamsburg, Virginia
• December 8, 2006
• Eric Weaver - FHWA

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What is It?

• Pavement Deflection Data Exchange (PDDX), .ddx
• A text data file format that can unify data
  reporting among different equipment, software and
  manufacturers
• A text data file format that also contains
  important information about equipment calibration

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What is the Problem?

• Current standard, PDDX-1, is incompatible with
  DARWin
• Manufacturers offer inconsistent versions of the
  DDX format.
• Current DDX does not include important
  calibration information
• Terminology within the standard is inaccurate or
  misleading

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What is the Significance?

• Unified file format allows sharing among
  different sources
• Unified file format allows transfer of data among
  different analysis applications
• Unified file format allows tracking equipment
  calibration information with time
• Deflection data is needed for rational design

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Recommended Changes

• Make compatible with DARWin move or repeat
  Delimiter and Decimal Symbol
• Add reference calibration information from the
  calibration centers
• Differentiate between manufacturer and
  calibration center information
• Remove information not stored by the FWD computer
• Include calibration center report information in
  the file or as an appendix to the standard

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What has been done?

• A new calibration system has been developed
• A file converter has been developed
• LTPP changed to DDX
• The PDDX-1 standard has been marked up with the
  recommended changes and recommendations
• FWD manufacturers have been consulted about the
  potential changes

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Related Efforts

• Use of FWD data with the MEPDG
• NCHRP 20-5(38-15) FWD Usage
• TPF-5(039) FWD Calibration
• FLHD FWD Operations and Analysis Guidelines
• LTPP FWD Maintenance and Operations Manuals
  January 2007

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Benefits

• Increased use of deflection data
• Enable sharing of deflection data
• Direct transfer of calibration results to FWD
  computer
• Better user access to LTPP FWD data sets
• Tracking of calibration information over time

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Path Forward

• Submit to Mergenmeier and let him handle it from
  here.
• Await SoM recommendation and include feedback
• Make adjustments to PDDX file converter and LTPP
  DDX file extractor
• Coordinate with FWD manufacturers to make
  adjustments to their software

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