Topic Notes 6--Rigid - TOPIC NOTES 6 THE AASHTO RIGID...

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1 TOPIC NOTES 6 THE AASHTO RIGID PAVEMENT DESIGN PROCEDURE (NEW OR RECONSTRUCTED) This SECTION is used to describe the AASHTO rigid pavement design procedure. Information is provided relative to the development of this procedure, as are various design examples. The required design input values are described and illustrated. U.S. customary units are used throughout these notes since the AASHTO design procedure currently uses these units. 1. BACKGROUND 1.1 AASHO ROAD TEST The basic information concerning the AASHO Road Test will not be repeated here; however, relevant information specific to how the rigid pavements performed at the Road Test will be. It is helpful in one's understanding of the AASHTO Design Guide to have such background information. 1.2 AASHTO DESIGN CRITERIA The primary design criterion is Present Serviceability Index (PSI). PSI was estimated for the Road Test pavement sections by use of the following equation [1]: PSI = 5.41 - 1.80 log(1 + SV ) - 0.9 C + P Eq. 6.1 where PSI = Present serviceability index, __ SV = mean of the slope variance in the two wheelpaths (measured with the CHLOE profilometer or BPR Roughometer), and C, P = measures of cracking and patching in the pavement surface, C = total linear feet of Class 3 and Class 4 cracks per 1000 ft 2 of pavement area. A Class 3 crack is defined as opened or spalled (at the surface) to a width of 0.25 in. (6 mm) or more over a distance equal to at least one-half the crack length. A Class 4 is defined as any crack which has been sealed. P = expressed in terms of ft 2 per 1000 ft 2 of pavement surfacing. The summary statistics for the above equation are: R 2 = 91.6 percent
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2 RMSE = 0.32 n = 49 data points The original data used to develop this equation is shown as Table 1 and is a good illustration of regression analysis (using actual data to develop a predictive equation). Were other forms of this equation possible? Certainly! Some of the different, possible regression equations follow: (a) PSR vs. log 10 (1 + __ SV ) Eq. 2 PSI = 5.92 - 2.61 log 10 (1 + __ SV ) R 2 = 88.8% RMSE = 0.37 n = 49 (b) PSR vs. C + P Eq. 3 PSI = 4.01 - 0.23 C + P R 2 = 81.2% RMSE = 0.48 n = 49 (c) PSR vs. __ SV Eq. 4 PSI = 3.84 - 0.05 __ SV R 2 = 73.9% RMSE = 0.57 n = 49 (d) PSR vs. C Eq. 5 PSI = 3.64 - 0.03C R 2 = 59.4% RMSE = 0.71 n = 49 (e) PSR vs. P Eq. 6 PSI = 3.08 - 0.02P R 2 = 26.2% RMSE = 0.95 n = 49
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3 Table 1. Data Used in the Development of AASHO Road Test Correlation Between PSR and PSI for Rigid Pavements [from Ref. 6.1] Transformations State Mean Panel PSR Mean Slope Variance in Wheelpath ( __ SV ) Cracking — Class 3 and Sealed cracks ft/1000 ft 2 (C) Patching — Patched Area ft/1000 ft 2 (P) log (1 + __ SV ) C + P Illinois 2.0 52.0 53 8 1.72 7.8 4.2 6.5 4 0 0.88 2.0 2.6 22.2 42 11 1.37 7.3 2.3 26.2 46 7 1.44 7.3 1.2 47.8 102 28 1.69 11.4 2.8 25.5 15 1 1.42 4.0 4.4 3.2 0 0 0.63 0.0 1.1 50.8 65 5 1.71 8.4 0.9 76.8 74 85 1.89 12.6 Minnesota 1.3 43.3 40 59 1.65 10.0 1.8 24.2 23 66 1.40 9.4 2.1 24.7 47 41 1.41 9.4 4.1 2.4 4 0 0.54 2.0 3.8 4.0 2 0 0.70 1.4 3.0 7.8 14 1 0.95 3.9 3.0 7.5 22 0 0.93 4.7 2.9 9.7 14 0 1.03 3.7 2.5 17.6 34 0 1.27 5.8 1.4 59.2 16 12 1.78 5.3 4.3 3.0 0 0 0 60 0.0 4.3 4.0 0 0 0.70 0.0 3.7 5.3 0 0 0.80 0.0 3.6 4.4 0 0 0.73 0.0 3.9 5.3 0 0 0.80 0.0 3.9 6.3 0 0 0.87 0.0 1.3 32.3 76 1 1.52 8.8 1.2 27.8 64 0 1.46 8.0 2.2 25.6 97 1 1.42 9.9 4.4 4.0 0 0 0.70 0.0 Indiana 4.0 6.6 0 0 0.88 0.0 3.8 6.6 11 0 0.88 3.3 3.6 6.8 2 0 0.89 1.4 3.2 9.8 1 2 1.03 1.7 2.6 14.6 72 0 1.19 8.5 2.8 10.4 70 1 1.06 8.4 1.8 49.4 41 29 1.70 8.4 1.8 54.5 42 37 1.74 8.9 2.1 36.6 50 29 1.58 8.9 2.2 25.1 86 33 1.42 10.9 1.8 45.4 40 65 1.67 10.2 2.7 9.9 81 5 1.04 9.3 4.2 6.1 0 0 0.85 0.0 4.3 5.2 0 0 0.79 0.0 4.3 7.1 0 0 0.91 0.0 1.2 81.9 54 219 1.92 16.5 2.2 32.2 36 0 1.52 6.0 4.3 4.6 0 0 0.75 0.0 2.8 12.6 5 13 1.13 4.2 2.7 17.8 5 16 1.27 4.6
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Topic Notes 6--Rigid - TOPIC NOTES 6 THE AASHTO RIGID...

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