MODIFIED NEWTON ALGORITHM FOR BACKCALCULATION OF PAVEMENT LAYER PROPERTIES

An efficient algorithm for the backcalculation of pavement layer moduli from measured surface deflections is presented. The algorithm is an iterative one and can use any mechanistic analysis program for forward calculations (presently an extended precision CHEVRON program is used for this purpose). Most mechanistic-based backcalculation methods attempt to find the layer moduli that minimize the weighted sum of the relative or absolute errors between measured and predicted surface deflections. Using a search technique to achieve such a minimization sometimes requires hundreds of calls to a mechanistic analysis program, and some programs try to speed this up by using a previously created data base. The algorithm presented here is different in that it uses a modified Newton method to obtain the least-squares solution of an overdetermined set of equations. This gives the proposed algorithm a robustness that some other approaches appear to lack. For example, the predicted moduli are not too sensitive to the initially assumed seed moduli or the location of the stiff layers (e.g., CRAM section, composite pavements, shallow or deep bedrock, etc.). Further, a set of auxiliary equations that are totally independent of those used in the modified Newton method and that relate surface deflections to the compressions in each pavement layer are used to improve the speed of convergence. The algorithm is also extended to improve incorrectly specified layer thicknesses. The algorithm is being implemented in a new backcalculation program named MICHBACK.

• Record URL:
  http://onlinepubs.trb.org/Onlinepubs/trr/1993/1384/1384-003.pdf
• Record URL:
  https://scholar.google.com/scholar_lookup?title=MODIFIED+NEWTON+ALGORITHM+FOR+BACKCALCULATION+OF+PAVEMENT+LAYER+PROPERTIES&author=R.+Harichandran&author=T.+Mahmood&author=A.+Raab&author=G.+Baladi&publication_year=1993
• Availability:
  • Find a library where document is available. Order URL: http://worldcat.org/isbn/0309054540
• Supplemental Notes:
  • This paper appears in Transportation Research Record No. 1384, Strength and Deformation Characteristics of Pavement Structures. Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. Copyright © National Academy of Sciences. All rights reserved
• Authors:
  • Harichandran, Ronald S
  • Mahmood, Tariq
  • Raab, A Robert
  • Baladi, Gilbert Y
• Publication Date: 1993

Language

• English

Media Info

• Features: Figures; References; Tables;
• Pagination: p. 15-22
• Monograph Title: Strength and deformation characteristics of pavement structures
• Serial:
  • Transportation Research Record
  • Issue Number: 1384
  • Publisher: Transportation Research Board
  • ISSN: 0361-1981

Subject/Index Terms

• TRT Terms: Algorithms; Backcalculation; Computer programs; Layer coefficient (Pavements); Mechanical analysis; Mechanistic design; Modulus; Pavement layers
• Uncontrolled Terms: Layer moduli
• Old TRIS Terms: Layer thicknesses
• Subject Areas: Data and Information Technology; Design; Highways; Pavements; I22: Design of Pavements, Railways and Guideways; I23: Properties of Road Surfaces;

Filing Info

• Accession Number: 00634494
• Record Type: Publication
• ISBN: 0309054540
• Files: TRIS, TRB, ATRI
• Created Date: Aug 18 1993 12:00AM