Determination of layer moduli from falling weight deflectometer measurements

Antti Ruotoistenmäki

Research output: Book/ReportReportProfessional

Abstract

Backcalculation programs are used for evaluation of pavement layer moduli from falling weight deflectometer (FWD) measurements. In this study, a comparison of two programs with different calculation methods, Modulus and Elmod, is made using deflection data derived from 43 SHRP-LTPP (Strategic Highway Research Program, Long-Term Pavement Performance) test sections. First, a brief look is made into the material models, which describe the behaviour of pavement layer materials. Basic concepts of the two backcalculation programs used in this study, Modulus and Elmod, are discussed, and collection of input data for the programs is described. From a comparison of backcalculated layer moduli from the two programs at Finnish standard wheel load of 50 kN, it is concluded that higher subgrade modulus values are obtained with the Elmod-program than with the Modulus-program. Consequently, the Modulus-program yields higher values for asphalt layer modulus than the Elmod-program. Variation in backcalculated layer moduli is somewhat greater within the Modulus-program than the Elmod-program. Stress-sensitivity of paving materials was studied by using the FWD at four different loading levels. The base course modulus was found to be the most stress-sensitive of pavement layers, since the stress level is also highest in the base course of unbound pavement layers. Critical strains were calculated using the linear program (BISAR) with layer moduli from the Modulus-program as input and with the Elmod-program. It was found, that calculated strains from the two programs agree very well, even though the calculated moduli are quite different. Calculated strains from FWD loading were compared with measured strains under moving wheel load from the field at Virttaa test site. The differences between the two are most likely due to differences in the loading conditions and in the method of analysis.
Original languageEnglish
Place of PublicationEspoo
PublisherVTT Technical Research Centre of Finland
Number of pages68
ISBN (Print)951-38-4486-2
Publication statusPublished - 1994
MoE publication typeNot Eligible

Publication series

NameVTT Tiedotteita - Meddelanden - Research Notes
PublisherVTT
No.1552
ISSN (Print)1235-0605
ISSN (Electronic)1455-0865

Fingerprint

Weighing
Pavements
Wheels
Asphalt
Loads (forces)

Keywords

  • backcalculation
  • flexible pavements
  • Falling weight deflectometer
  • FWD
  • measurement
  • layers
  • modulus of elasticity
  • models
  • deflection
  • comparison
  • subgrades
  • Elmod
  • Modulus
  • strains
  • SHRP
  • LTPP
  • stress sensitivity
  • nondestructive testing
  • NDT

Cite this

Ruotoistenmäki, A. (1994). Determination of layer moduli from falling weight deflectometer measurements. Espoo: VTT Technical Research Centre of Finland. VTT Tiedotteita - Meddelanden - Research Notes, No. 1552
Ruotoistenmäki, Antti. / Determination of layer moduli from falling weight deflectometer measurements. Espoo : VTT Technical Research Centre of Finland, 1994. 68 p. (VTT Tiedotteita - Meddelanden - Research Notes; No. 1552).
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Ruotoistenmäki, A 1994, Determination of layer moduli from falling weight deflectometer measurements. VTT Tiedotteita - Meddelanden - Research Notes, no. 1552, VTT Technical Research Centre of Finland, Espoo.

Determination of layer moduli from falling weight deflectometer measurements. / Ruotoistenmäki, Antti.

Espoo : VTT Technical Research Centre of Finland, 1994. 68 p. (VTT Tiedotteita - Meddelanden - Research Notes; No. 1552).

Research output: Book/ReportReportProfessional

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N2 - Backcalculation programs are used for evaluation of pavement layer moduli from falling weight deflectometer (FWD) measurements. In this study, a comparison of two programs with different calculation methods, Modulus and Elmod, is made using deflection data derived from 43 SHRP-LTPP (Strategic Highway Research Program, Long-Term Pavement Performance) test sections. First, a brief look is made into the material models, which describe the behaviour of pavement layer materials. Basic concepts of the two backcalculation programs used in this study, Modulus and Elmod, are discussed, and collection of input data for the programs is described. From a comparison of backcalculated layer moduli from the two programs at Finnish standard wheel load of 50 kN, it is concluded that higher subgrade modulus values are obtained with the Elmod-program than with the Modulus-program. Consequently, the Modulus-program yields higher values for asphalt layer modulus than the Elmod-program. Variation in backcalculated layer moduli is somewhat greater within the Modulus-program than the Elmod-program. Stress-sensitivity of paving materials was studied by using the FWD at four different loading levels. The base course modulus was found to be the most stress-sensitive of pavement layers, since the stress level is also highest in the base course of unbound pavement layers. Critical strains were calculated using the linear program (BISAR) with layer moduli from the Modulus-program as input and with the Elmod-program. It was found, that calculated strains from the two programs agree very well, even though the calculated moduli are quite different. Calculated strains from FWD loading were compared with measured strains under moving wheel load from the field at Virttaa test site. The differences between the two are most likely due to differences in the loading conditions and in the method of analysis.

AB - Backcalculation programs are used for evaluation of pavement layer moduli from falling weight deflectometer (FWD) measurements. In this study, a comparison of two programs with different calculation methods, Modulus and Elmod, is made using deflection data derived from 43 SHRP-LTPP (Strategic Highway Research Program, Long-Term Pavement Performance) test sections. First, a brief look is made into the material models, which describe the behaviour of pavement layer materials. Basic concepts of the two backcalculation programs used in this study, Modulus and Elmod, are discussed, and collection of input data for the programs is described. From a comparison of backcalculated layer moduli from the two programs at Finnish standard wheel load of 50 kN, it is concluded that higher subgrade modulus values are obtained with the Elmod-program than with the Modulus-program. Consequently, the Modulus-program yields higher values for asphalt layer modulus than the Elmod-program. Variation in backcalculated layer moduli is somewhat greater within the Modulus-program than the Elmod-program. Stress-sensitivity of paving materials was studied by using the FWD at four different loading levels. The base course modulus was found to be the most stress-sensitive of pavement layers, since the stress level is also highest in the base course of unbound pavement layers. Critical strains were calculated using the linear program (BISAR) with layer moduli from the Modulus-program as input and with the Elmod-program. It was found, that calculated strains from the two programs agree very well, even though the calculated moduli are quite different. Calculated strains from FWD loading were compared with measured strains under moving wheel load from the field at Virttaa test site. The differences between the two are most likely due to differences in the loading conditions and in the method of analysis.

KW - backcalculation

KW - flexible pavements

KW - Falling weight deflectometer

KW - FWD

KW - measurement

KW - layers

KW - modulus of elasticity

KW - models

KW - deflection

KW - comparison

KW - subgrades

KW - Elmod

KW - Modulus

KW - strains

KW - SHRP

KW - LTPP

KW - stress sensitivity

KW - nondestructive testing

KW - NDT

M3 - Report

SN - 951-38-4486-2

T3 - VTT Tiedotteita - Meddelanden - Research Notes

BT - Determination of layer moduli from falling weight deflectometer measurements

PB - VTT Technical Research Centre of Finland

CY - Espoo

ER -

Ruotoistenmäki A. Determination of layer moduli from falling weight deflectometer measurements. Espoo: VTT Technical Research Centre of Finland, 1994. 68 p. (VTT Tiedotteita - Meddelanden - Research Notes; No. 1552).