Pavement Design - II.pdf
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(2) FUNDEMENTALS. Mechanistic-Empirical (M-E) Design . Primary advantage is the consideration of the state of stress. HMA Base Subbase Subgrade Soil. FUNDEMENTALS. Mechanistic-Empirical (M-E) Design . Establishes connection between distress and distress mechanism. FUNDEMENTALS. Mechanistic-Empirical (M-E) Design Accounts for new materials, traffic loads, and construction procedures All design features affecting pavement performance considered Relies more on fundamental engineering mechanics Primary focus on pavement performance . 2.
(3) FUNDEMENTALS. Mechanistic-Empirical (M-E) Design . 1993 AASHTO Guide Design Variables – – – – – –. Time Traffic Reliability Environment Serviceability Structural Number. FUNDEMENTALS. Mechanistic-Empirical (M-E) Design. FUNDEMENTALS. AASHTO Design Time. Constraints. – Performance Period Refers. to the time that an initial pavement structure will last before rehab. – Analysis Period Refers. to the period of time that any design strategy must cover. 3.
(4) FUNDEMENTALS. AASHTO Design . Traffic – Equivalent Single Axle Load (ESAL) Converts. wheel loads of various magnitudes and repetitions to an equivalent number of "standard" or "equivalent" loads based on the amount of damage they do to the pavement. FUNDEMENTALS. AASHTO Design . Equivalent Axle Load Factor (EALF) – Damage per pass to a pavement by the axle in question relative to the damage per pass of a standard axle load – Depends of type of pavements, thickness or structural capacity and terminal conditions. FUNDEMENTALS. EALF Table for Flexible Pavement, Single Axle & pt of 2.5 Pavement Structural Number (SN) Axle Load (kips) 2 4 6 8 10 12 14 16. 1. 2. 3. 4. 5. 6. 0.004 0.003 0.011 0.032 0.078 0.168 0.328 0.591. 0.004 0.004 0.017 0.047 0.102 0.198 0.358 0.613. 0.003 0.004 0.017 0.051 0.118 0.229 0.399 0.646. 0.002 0.003 0.013 0.041 0.102 0.213 0.388 0.645. 0.002 0.002 0.010 0.034 0.088 0.189 0.360 0.623. 0.002 0.002 0.009 0.031 0.080 0.176 0.342 0.606. 4.
(5) FUNDEMENTALS. AASHTO Design . m. . i =1. . ESAL = ∑ Fi ni. m = number of axle load groups Fi = the EALF for the ith axle load group ni = number of passes of the ith axle load group. FUNDEMENTALS. 200X AASHTO Design Guide . . No more ESALs Traffic input – Vehicle type (number of axles) – Axle weight Quantity and quality of raw traffic data similar to that used to compute ESALS – Consistent with FHWA Traffic Monitoring Guide. FUNDEMENTALS. Traffic Hierarchical Input Levels. Input Level. Input Values. Knowledge of Parameters. 1. Site specific WIM & AVC. Good. 2 3. Regional Default WIM & AVC, Vehicle Counts National Default WIM & AVC, Vehicle Counts. Modest Poor. 5.
(6) 200X AASHTO Design Guide Load Spectra – Axle weight frequencies for each common axle combination (e.g. single axle, tandem axle, tridem axle, quad axle).. 800. 700. 600. Number of Axles. FUNDEMENTALS. . 500. 400 300. 200. 100. 0 0. 5000. 10000. 15000. 20000. 25000. 30000. 35000. 40000. 45000. 50000. 55000. 60000. 65000. 70000. 75000. 80000. Axle Load (lbs). FUNDEMENTALS. AASHTO Design . Reliability - Incorporating some degree of certainty into the design process to ensure that various design alternatives will last the Analysis Period Recommended Level of Reliability Functional Classificaiton. Urban. Rural. Interstate Arterials Collectors Local. 85 - 99.9 80 - 99 80 - 95 50 - 80. 80 - 99.9 75 - 95 75 - 95 50 - 80. FUNDEMENTALS. AASHTO Design Environmental. – Temperature Stresses. induced by thermal action Changes in creep properties Effect of freezing and thawing of subgrade. – Rainfall Penetration. of surface water into underlying. materials. 6.
(7) FUNDEMENTALS. AASHTO Design Serviceability. – Initial serviceability index is function of pavement type and construction quality – Terminal serviceability index is lowest index that will be tolerated before rehab, resurfacing, or reconstruction. SURFACE (AC). AASHTO Design. BASE. FUNDEMENTALS. SUBBASE (OPTIONAL). . Structural Number. SUBGRADE. – mi = drainage coefficient for layer i – a1, a2, a3 = layer coefficient representative of surface, base, and subbase course, respectively – D1, D2, D3 = thickness representative of surface, base, and subbase course, respectively. SN = a1D1 + a2 D2 m2 + a3 D3 m3. FUNDEMENTALS. AASHTO Design Example Ridgeview. Dr. Rehabilitation. – 20-year flexible pavement analysis period – Low volume road with limited growth potential. 7.
(8) NAM ED. M PLU. VIEW. COPPER POINT. R IDGE. AS. FUNDEMENTALS. C OPP. ER PO INT. COPPER POINT. GREEN RANCH. V GE IE W. D ME TA. ADO W HEIG. IN VIS. WINDY M. MOU N TA. NS CR EE. HTS. GREEN RA NCH. RID. NA UN. RIDGEVIEW. UM PL. W VIE GE. AS. RID COPPER. Traffic. – 72-hour vehicle counts were conducted directionally at three locations within the project boundaries using machine traffic counters – Manual classification counts were conducted at the machine count locations to “calibrate” the machine count data and categorize into the FHWA 13 vehicle classification scheme. Vehicle Classification. FUNDEMENTALS. AASHTO Design Example. 8.
(9) Adjusted Traffic Volumes and Vehicle Classification Year 2005 Through 2010 Road Segment:. Ridgeview Drive @ Plumas Street Class 1. EB. Class 2. % Volume. WB. Volume. Class 3. Class 4. Class 5. Class 6 0.15. Class 9. Total. 43.64. 54.11. 0.35. 1.60. 0.15. 100. 1132.30. 1404.00. 9.10. 41.60. 3.90. 3.90. 2594.8. 43.29. 54.11. 0.70. 1.60. 0.15. 0.15. 100. 1123.20. 1404.00. 18.20. 41.60. 3.90. 3.90. 2594.8. %. 5189.6 Road Segment:. Class 1. FUNDEMENTALS. Total ADT. Ridgeview Drive @ Mountain Vista Way. EB. Class 2. %. 43.44. Volume WB. Class 3. 823.65. 54.11 1026.00. Class 4. Class 5. 0.45. 1.60. 8.55. 30.40. Class 6 0.20. Class 9. Total. 0.20. 100. 3.80. 3.80. %. 42.94. 54.11. 0.95. 1.60. 0.20. 0.20. 100. Volume. 814.15. 1026.00. 18.05. 30.40. 3.80. 3.80. 1896.2. 1896.2. 3792.4. Total ADT. Adjusted Traffic Volumes and Vehicle Classification Year 2011 Through 2025 Road Segment:. Ridgeview Drive @ Plumas Street Class 1. EB. % Volume. WB. % Volume. Class 2. Class 3. Class 4. Class 5. 43.94. 54.11. 0.35. 1.60. 1140.10. 1404.00. 9.10. 41.60. 43.59. 54.11. 0.70. 1.60. 1131.00. 1404.00. 18.20. 41.60. Class 6. Class 9. 0.00. 0.00. 0.00. 0.00. Total 100 2594.8 100 2594.8 5189.6. Road Segment:. Total ADT. Ridgeview Drive @ Mountain Vista Way Class 1. EB WB. Class 2. Class 3. Class 4. Class 5. %. 43.84. 54.11. 0.45. 1.60. Volume. 831.25. 1026.00. 8.55. 30.40. %. 43.34. 54.11. 0.95. 1.60. Volume. 821.75. 1026.00. 18.05. 30.40. Class 6. Class 9. 0.00. 0.00. 0.00. 0.00. Total 100 1896.2 100 1896.2 3792.4. Total ADT. AASHTO Design Example FUNDEMENTALS. Compute ESALs using EALFs from AASHTO Tables in Appendix D Assumptions . – Typical axle weights for each vehicle class – SN of 3.0 – pt of 2.5. WB Daily ESALs. 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025. 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20. WB Yearly ESALs. Cumulative ESALs. Plumas. Mountain Vista. Plumas. Mountain Vista. Plumas. Mountain Vista. 90 90 90 90 90 90 75 75 75 75 75 75 75 75 75 75 75 75 75 75 75. 81 81 81 81 81 81 66 66 66 66 66 66 66 66 66 66 66 66 66 66 66. 33,031 33,031 33,031 33,031 33,031 33,031 27,362 27,362 27,362 27,362 27,362 27,362 27,362 27,362 27,362 27,362 27,362 27,362 27,362 27,362 27,362. 29,487 29,487 29,487 29,487 29,487 29,487 23,963 23,963 23,963 23,963 23,963 23,963 23,963 23,963 23,963 23,963 23,963 23,963 23,963 23,963 23,963. 33,031 66,062 99,093 132,124 165,155 198,187 225,548 252,910 280,271 307,633 334,994 362,356 389,717 417,079 444,441 471,802 499,164 526,525 553,887 581,248 608,610. 29,487 58,973 88,460 117,947 147,433 176,920 200,882 224,845 248,807 272,770 296,732 320,695 344,657 368,620 392,582 416,545 440,507 464,470 488,432 512,395 536,357. 9.
(10) FUNDEMENTALS. AASHTO Design Example . Materials – R-value data was collected at five sample locations (8, 7, 10, 20, 8) – Resilient Modulus (MR) relationship. R-value ≤ 20 MR = 1000 + 555 x R-value (psi). Parameter Design Life, years Traffic (ESALs), W18 Reliability, R (%). Average 20 610,000 80%. Standard Deviation (New Construction), So. 0.45. Subgrade R-value. 10.60. Subgrade Resilient Modulus, MR (ksi). 6.9. Initial Serviceability, P0. 4.2. Terminal Serviceability, Pt. 2.5. Modulus of Elasticity for New AC (ksi). 350. Layer Coefficient for New Plant Mix Surface (AC), a1. 0.39. Layer Coefficient for Gravel Base, a2. 0.14. Layer Coefficient for Subbase (Borrow), a3. 0.08. Drainage Coefficient for AC layer, m1. 1.0. Drainage Coefficient for Base layer, m2. 1.1. Drainage Coefficient for SB layer, m3. 1.1. SN ≈ 3.1. 10.
(11) AASHTO Design. SURFACE (AC) BASE. FUNDEMENTALS. SUBGRADE. . Assume D values for surface and base – Asphalt is 4 inches – Base is 10 inches. . Calculate SN - Is it acceptable?. SN = a1D1 + a2 D2 m2 SN = 0.39 × 4.0 in + 0.14 × 10 in × 1.1 SN = 3.1. Topics . Introduction – Design Factors – Pavement Types. . Fundamentals of Pavement Design – AASHTO – Asphalt Institute. FUNDEMENTALS. Asphalt Institute (AI) Design . Determine minimum thickness of asphalt layer that will adequately withstand the stresses that develop for two strain criteria – Vertical compressive strain at surface of subgrade – Horizontal tensile strain at bottom of asphalt layer. 11.
(12) Asphalt Institute (AI) Design FUNDEMENTALS. Wheel load. P0 P1. P1 SUBGRADE. Stress distribution within different layers of the pavement structure. General form of stress reduction. Asphalt Institute (AI) Design FUNDEMENTALS. Wheel load. SUBGRADE. Tension Compression. FUNDEMENTALS. Asphalt Institute (AI) Design . 20% Fatigue. Design Criteria – Fatigue Nf. = allowable number of load repetitions = dynamic modulus ∈t = horizontal tensile strain at the bottom of the asphalt layer Assumes asphalt volume of 11% and air void volume of 5% |E*|. Nf = 0.0796(∈t)-3.291 |E*|-0.854. 12.
(13) FUNDEMENTALS. Asphalt Institute (AI) Design . 0.5 inch. Design Criteria – Permanent Deformation Nd. = allowable number of load repetitions = vertical compressive strain on the surface of the subgrade. ∈c. Nd = 1.365 x 10-9 (∈c)-4.477. FUNDEMENTALS. Asphalt Institute (AI) Design . Five main steps 1. 2. 3. 4.. Select or determine input data Select surface and base materials Determine minimum thickness required Evaluate feasibility of staged construction and prepare plan, if necessary 5. Carry out economic analyses. NAM ED. M PLU. VIEW. COPPER POINT. R IDGE. AS. C OPP. ER PO INT. IE W. TA. ADO W HEIG. IN VIS. WINDY M. MOU N TA. NS CR EE. HTS. GREEN RA NCH. V GE. D ME. RIDGEVIEW. COPPER POINT. GREEN RANCH. RID. NA UN. FUNDEMENTALS. UM PL. W VIE GE. AS. RID COPPER. 13.
(14) FUNDEMENTALS. Asphalt Institute (AI) Design Example Gross . Select or determine input data – Traffic Characteristics – ESALs similar to AASHTO. WB Daily ESALs. 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025. 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20. Axle Load (kips) 1 2 4 6 8 10 12 14 16. WB Yearly ESALs. Single Tandem Tridem Axles Axles Axles 0.00002 0.00018 0.00209 0.0003 0.01043 0.001 0.00030 0.0343 0.003 0.001 0.0877 0.007 0.002 0.189 0.014 0.003 0.360 0.027 0.006 0.623 0.047 0.011. Cumulative ESALs. Plumas 2. Plumas 2. Plumas 2. 118 118 118 118 118 118 72 72 72 72 72 72 72 72 72 72 72 72 72 72 72. 43,110 43,110 43,110 43,110 43,110 43,110 26,197 26,197 26,197 26,197 26,197 26,197 26,197 26,197 26,197 26,197 26,197 26,197 26,197 26,197 26,197. 43,110 86,221 129,331 172,441 215,552 258,662 284,859 311,057 337,254 363,451 389,649 415,846 442,043 468,241 494,438 520,635 546,833 573,030 599,227 625,425 651,622. FUNDEMENTALS. Asphalt Institute (AI) Design Example Select. or determine input data. – R-value data was collected at five sample locations (8, 7, 10, 20, 8) – Resilient Modulus (MR) relationship MR = 1155 + 555 x R-value (psi). 14.
(15) FUNDEMENTALS. Asphalt Institute (AI) Design Example Select. surface and base materials. – Asphalt concrete surface or emulsified asphalt surface – Asphalt concrete base, emulsified asphalt base, or untreated aggregate base. FUNDEMENTALS. Asphalt Institute (AI) Design Example . Determine minimum thickness required – Obtained by computer program – Entering the appropriate table or chart Assume. 10 inch untreated aggregate base MR of 7 psi Design ESAL of 655,000 Subgrade. 6.5 inch. 15.
(16) FUNDEMENTALS. Asphalt Institute (AI) Design Example Evaluate. feasibility of staged construction and prepare plan, if necessary – Used when adequate funds are not available to construct the pavement to the “required” depth. FUNDEMENTALS. Asphalt Institute (AI) Design Example Carry. out economic analyses. – Evaluate alternative designs based on the type of pavement, type of materials used, whether or not staged construction is used, etc.. FUNDEMENTALS. Questions. 16.
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