A MICROCOMPUTER BASED PROCEDURE FOR BACKCALCULATING LAYER MODULI FROM FWD DATA. INTERIM REPORT

The purpose of this report is to describe a backcalculation procedure (MODULUS) developed to interpret Falling Weight Deflectometer (FWD) data and to illustrate how this procedure was built into a pavement analysis system for the Texas State Department of Highways and Public Transportation. MODULUS is microcomputer based and can be used on 2-, 3-, or 4-layer pavement systems. It used a linear-elastic program to generate a database of deflection bowls; in a four-layer system, a minimum of 27 runs (3 x 3 x 3 moduli values for surface, base, and subgrade) would be performed. The size of the database depends on the user-supplied range of acceptable modulus values for each layer. Once the database is generated, a pattern search routine is used to fit measured and calculated bowls; error minimization is very rapid, less than 5 seconds per bowl on a 386-type microcomputer.

• Supplemental Notes:
  • Research study title: Nondestructive Test Procedures for Analyzing the Structural Condition of Pavements.
• Corporate Authors:

  Texas Transportation Institute

  Texas A&M University System, 1600 E Lamar Boulevard
  Arlington, TX  United States  76011

  Texas State Department of Highways & Public Transportation

  Transportation Planning Division, P.O. Box 5051
  Austin, TX  United States  78763

  Federal Highway Administration

  1200 New Jersey Avenue, SE
  Washington, DC  United States  20590
• Authors:
  • Uzan, J
  • Scullion, T
  • Michalek, C H
  • Parades, M
  • Lytton, R L
• Publication Date: 1988-9

Media Info

• Features: Appendices; Figures; References; Tables;
• Pagination: 82 p.

Subject/Index Terms

• TRT Terms: Backcalculation; Case studies; Databases; Deflection; Falling weight deflectometers; Information processing; Linear elasticity; Microcomputers; Modulus of elasticity; Pavement layers; Pavements
• Old TRIS Terms: Pavement deflection
• Subject Areas: Data and Information Technology; Design; Highways; Pavements; I22: Design of Pavements, Railways and Guideways;

Filing Info

• Accession Number: 00482291
• Record Type: Publication
• Report/Paper Numbers: FHWA/TX-88/1123-1, Res Rept 1123-1, TTI: 2-18-87-1123-1
• Contract Numbers: Study 2-18-87-1123
• Files: TRIS, USDOT, STATEDOT
• Created Date: Apr 30 1989 12:00AM