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    <copyright>Copyright © 2026. National Academy of Sciences. All rights reserved.</copyright>
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    <managingEditor>tris-trb@nas.edu (Bill McLeod)</managingEditor>
    <webMaster>tris-trb@nas.edu (Bill McLeod)</webMaster>
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      <title>Transport Research International Documentation (TRID)</title>
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      <title>THE DEVELOPMENT OF ROADHOG, A FLEXIBLE PAVEMENT OVERLAY DESIGN PROCEDURE. NDT OVERLAY DESIGN. FINAL REPORT</title>
      <link>https://trid.trb.org/View/363892</link>
      <description><![CDATA[A flexible pavement overlay thickness design procedure was developed.  The procedure follows the AASHTO structural number approach to flexible pavement design and uses the structural deficiency concept in selecting the overlay thickness.  The subgrade resilient modulus (M sub r) and existing pavement structural capacity (effective structural number or SN sub eff) are determined from NDT data obtained using a falling weight deflectometer.  M sub r is calculated using the deflection measured 3 ft from the FWD center of loading.  This method of calculation is based on ILLIPAVE finite element pavement analyses and was selected following an evaluation of various available NDT backcalculation methods.  SN sub eff is determined from the difference between the deflections at the center of loading and the deflection at a distance from the center equal to the total pavement thickness.  The SN sub eff determination method was developed under this study.  The complete procedure is programmed for use on an IBM PC, XT, AT, or any compatible system having at least one floppy disk drive and a minimum of 384K of available RAM.  The program is user friendly and runs interactively.  It is menu-driven and features on-line help facilities.]]></description>
      <pubDate>Fri, 31 May 1996 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/363892</guid>
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      <title>COMPARISON OF AASHTO AND ROADHOG FLEXIBLE PAVEMENT OVERLAY DESIGN PROCEDURES</title>
      <link>https://trid.trb.org/View/451809</link>
      <description><![CDATA[A comparison of the ROADHOG and AASHTO (1993) overlay design procedures for conventional flexible pavements is presented. Both procedures use a structural deficiency approach to overlay design yet differ in the methods used to estimate the effective structural number of an existing pavement and to estimate the in situ subgrade resilient modulus.  Both methods use pavement surface deflections to backcalculate or estimate required design parameters.  Specific comparisons include backcalculated subgrade resilient modulus, effective structural number, and recommended overlay thickness for a number of conventional flexible pavement configurations.  Pavement surface deflections are generated using the ILLI-PAVE finite-element pavement model and the ELSYM5 elastic layer model.  Pavement parameters varied to establish the deflection data base, including asphalt concrete surface thickness and resilient modulus, base course thickness and resilient modulus, and subgrade resilient modulus. The comparisons show that the AASHTO overlay design procedure recommends thicker overlays than does the ROADHOG procedure for pavements overlying relatively stiff subgrade soils.  The difference in recommended overlay thickness is linked to differences in the estimates of both SN sub f, the structural number required to carry future traffic, and SN sub eff, the effective structural number of the existing pavement.  The two design procedures recommend similar overlay thicknesses for pavements overlying soils with relatively low resilient modulus values.  The analyses also show that the backcalculated value of subgrade resilient modulus plays a larger role in determining the overlay thickness for the AASHTO procedure than for the ROADHOG procedure.]]></description>
      <pubDate>Tue, 07 Nov 1995 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/451809</guid>
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      <title>EFFECTIVE STRUCTURAL NUMBER ALGORITHM ENHANCEMENTS TO ROADHOG</title>
      <link>https://trid.trb.org/View/427211</link>
      <description><![CDATA[ROADHOG is a deflection-based flexible pavement overlay design procedure used by the Arkansas Highway and Transportation Department.  It uses a structural deficiency approach to overlay design modeled after the guidelines given in the 1986 AASHTO "Guide for Design of Pavement Structures".  The effective structural capacity of the existing pavement (SN sub eff) is calculated as a function of the difference in the maximum pavement deflection and a deflection at some radial distance from the point of loading.  This deflection difference is termed delta-D.  As originally developed ROADHOG is limited to the structural thickness design of asphalt concrete (AC) overlays for existing conventional flexible pavements (AC surface, granular base, subgrade).  Research has enhanced ROADHOG by adding capabilities to determine the SN sub eff for full-depth asphalt (FDA) pavements and surface-treated pavements (STPs). These enhancements allow the use of ROADHOG for any flexible pavement.  The SN sub eff algorithm for FDA pavements uses a delta-D approach similar to the algorithm currently used in ROADHOG for conventional flexible payments.  SN sub eff is determined for STPs by using a deflection ratio, delta-D/D0, in which D0 is the maximum pavement deflection under load.  The algorithms are developed by using a comprehensive deflection basin data base generated by the finite-element pavement model ILLI-PAVE, varying surface and base course thickness and stiffness and subgrade stiffness.  In both the FDA and STP algorithms the subgrade stiffness is not considered explicitly for estimating SN sub eff.  SN sub eff estimates for surface-treated pavements also do not explicitly include the granular layer thickness of the STP.  Comparisons of the new SN sub eff algorithms with the current procedures in ROADHOG indicate that the new algorithms give more consistent and accurate estimates of the effective structural number of the existing pavement.]]></description>
      <pubDate>Thu, 24 Aug 1995 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/427211</guid>
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      <title>INFLUENCE OF STRESS LEVELS AND SEASONAL VARIATIONS ON IN SITU PAVEMENT LAYER PROPERTIES</title>
      <link>https://trid.trb.org/View/415071</link>
      <description><![CDATA[Presented is a small-scale investigation of how stress levels and seasonal variations affect pavement layer characteristics. Monitoring such effects is basic to the effort conducted under the Strategic Highway Research Program (SHRP) Long-Term Pavement Performance (LTPP) studies currently under the FHWA jurisdiction.  Illustrated are the influences of stress levels, seasonal temperature variations, seasonal moisture variations, and accumulated equivalent single axle loads (ESALs) on (a) center deflection (D sub o) measured by the falling-weight deflectometer; (b) in situ asphalt concrete modulus (E sub AC); (c) in situ granular layer modulus (E sub g); (d) in situ subgrade resilient modulus (MR); (e) in situ AASHTO effective structural number (SN sub eff); and (f) variability within a section for each of the structural factors above.  Analysis of results suggests that MR is the parameter most affected by a change in stress level, followed by E sub g, E sub AC, and SN sub eff.  On the other hand, E sub AC is the parameter most affected by the change in temperature, followed by D sub o, SN sub eff, E sub g and MR.  Variations in MR and E sub g with temperature are believed to be associated indirectly with variations in E sub AC and temperature.  Changes in E sub AC and temperature result in changes in stress levels imposed on the underlying pavement layers that cause variations in MR and E sub g.  Accumulation of ESALs under dry conditions affect E sub AC, followed by D sub o, E sub g, SN sub eff, and MR, in order of diminishing effect.  In addition, seasonal moisture variations affect D sub o and MR, followed by E sub g, E sub AC and SN sub eff.  And variability within a section for each of the structural factors increases with an increase in temperature, moisture level, or accumulated ESALs.  Among the structural factors, SN sub eff has the lowest within-section variability, whereas E sub g has the greater within-section variability.]]></description>
      <pubDate>Thu, 23 Feb 1995 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/415071</guid>
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      <title>ROADHOG.EXE USER'S MANUAL</title>
      <link>https://trid.trb.org/View/363893</link>
      <description><![CDATA[This report is a user's manual for ROADHOG, a computerized procedure for the structural design of asphalt overlays for flexible pavements.  The procedure, developed for the Arkansas State Highway and Transportation Department, uses NDT data from a falling weight deflectometer.  It follows the AASHTO structural number approach to flexible pavement design and uses the structural deficiency concept in selecting the overlay thickness.  The total required structural number is determined using the design-performance equation contained in the 1986 AASHTO Guide.  The subgrade resilient modulus is determined from NDT data using equations developed from ILLIPAVE.  The effective structural number of the existing pavement is determined from a procedure developed for ROADHOG involving a relationship between the effective structural number and a quantity "delta D".  Delta D is defined as the difference between the surface deflections at the center of loading and at a distance from the center of loading equal to the total pavement thickness.  The ROADHOG program is user friendly and runs interactively.  It is menu-driven and features on-line help screens.  It will run on an an IBM PC, XT, AT, or any 100% compatible system having at least one floppy disk drive and a minimum of 384K of available RAM.]]></description>
      <pubDate>Sun, 31 May 1992 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/363893</guid>
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