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Dr. Wa'el M. Albawwab ECGD4228 Transportation Engineering II Summer 2008 Saturdays 15:30-18:30 PM K204.

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Presentation on theme: "Dr. Wa'el M. Albawwab ECGD4228 Transportation Engineering II Summer 2008 Saturdays 15:30-18:30 PM K204."— Presentation transcript:

1 Dr. Wa'el M. Albawwab ECGD4228 Transportation Engineering II Summer 2008 Saturdays 15:30-18:30 PM K204

2 Dr. Wa'el M. Albawwab  Pavement Design Methods  Design Parameters  Flexible Pavement  Rigid Pavement Lecture 6

3 Dr. Wa'el M. Albawwab A pavement consists of a number of layers of different materials A pavement consists of a number of layers of different materials Pavement Design Methods: Pavement Design Methods:  AASHTO Method  The Asphalt Institute Method for Flexible Pavements  Portland Cement Association (PCA) Method for Concrete Pavements  Texas DOT Method  Other methods Pavement Design Methods

4 Dr. Wa'el M. Albawwab AASHTO Road Test AASHTO: American Association of State Highway and Transportation Officials AASHTO: American Association of State Highway and Transportation Officials Objective: To relate axle load repetitions, pavement design configurations & distresses Objective: To relate axle load repetitions, pavement design configurations & distresses

5 Dr. Wa'el M. Albawwab ASSHTO Design Method  Pavement Performance  Traffic  Roadbed soils (subgrade materials)  Materials of construction  Environment  Drainage  Reliability  Shoulder Design  Life-Cycle Costs

6 Dr. Wa'el M. Albawwab AASHTO’s Formula Considers: (1) Pavement Performance Based on Pavement Serviceability conceptBased on Pavement Serviceability concept  Serviceability was defined as the ability of a pavement to serve its intended function under existing conditions During the test, road users rated pavementsDuring the test, road users rated pavements  Pavement Serviceability Rating (PSR)  Based on the pavement roughness  0-1: Very Poor; 1-2: Poor; 2-3: Fair; 3-4: Good; and 4-5: Very Good 4-5: Very Good

7 Dr. Wa'el M. Albawwab  PSR’s used to develop design equations to predict  Present Serviceability Index (PSI) Initial Serviceability Index = p 0 (the servceability immediately after the construction of the pavement, recommended Terminal Serviceability = p t (2.5-major, 2.0-other), the minimum acceptable serviceability before resurfacing or reconstruction is needed. In the formula: Serviceability loss (  PSI) = p 0 – p t AASHTO’s Formula Considers: (1) Pavement Performance

8 Dr. Wa'el M. Albawwab Pavement Condition Defined by users (drivers) Defined by users (drivers) Develop methods to relate physical attributes to driver ratings Develop methods to relate physical attributes to driver ratings Result is usually a numerical scale Result is usually a numerical scale From the AASHO Road Test (1956 – 1961)

9 Dr. Wa'el M. Albawwab Typical PSI vs. Time Time Serviceability (PSI) p0p0 ptpt p 0 - p t Terminal Serviceability Level

10 Dr. Wa'el M. Albawwab The concept of ESAL – Equivalent Single-Axel Load The concept of ESAL – Equivalent Single-Axel Load  The traffic characteristics are determined in terms of the number of repetitions of an 18,000 single-axle load applied to the pavement on two sets of dual tires.  Expressed in Equivalent 18-kip Single Axle Loads (W 18 )  Axle load equivalency factor was introduced to convert different axle loads to Equivalent 18,000 lb (18-kip) Single Axle Loads. AASHTO’s Formula Considers: (2) Traffic

11 Dr. Wa'el M. Albawwab Vehicle Types

12 Dr. Wa'el M. Albawwab Vehicle Weight & Size Limits Weight limits for whole vehicle, single axles & tandem axles Size limits for length, width & height

13 Dr. Wa'el M. Albawwab By Load Equivalency Factors (F E ), i.e., number of repetition of 18 kip single-axle load. By Load Equivalency Factors (F E ), i.e., number of repetition of 18 kip single-axle load. ESAL Determination Axels (lb) SingleTandemTridem

14 Dr. Wa'el M. Albawwab Load Quantification Load Equivalency Load Equivalency –Generalized fourth power approximation

15 Dr. Wa'el M. Albawwab For each axle category i; (single, tandem, tridem) For each axle category i; (single, tandem, tridem) For all categories: For all categories: ESAL Determination

16 Dr. Wa'el M. Albawwab f d – design lane factor, which is the portion of total ESAL acting on the design lane (any lane of two lane highway and outside lane of multilane highway), from field data. G – traffic growth factor for a specific design period AADT – first year AADT N – number of axles (each axle will repeat one load when vehicle is moving) F E – Load equivalency factor ESAL Determination

17 Dr. Wa'el M. Albawwab Resilient Modulus (Mr) of the soil is considered in design, the value of Mr is normally known/given for design Resilient Modulus (Mr) of the soil is considered in design, the value of Mr is normally known/given for design Another parameter needs to know but not directly used in the AASHTO’s formula is CBR – California Bearing Ratio, which is a parameter indicative of soil’s strength. Relationship between Mr and CBR (or R value) is given by: Another parameter needs to know but not directly used in the AASHTO’s formula is CBR – California Bearing Ratio, which is a parameter indicative of soil’s strength. Relationship between Mr and CBR (or R value) is given by: Mr = 1500 CBR (for soils with CBR ≤ 10) Mr = 1500 CBR (for soils with CBR ≤ 10) Mr = CBR ( for 10 < CBR ≤ 20) Mr = CBR ( for 10 < CBR ≤ 20) AASHTO’s formula considers: (3) Subgrade materials

18 Dr. Wa'el M. Albawwab SN – The Structural Number SN – The Structural Number AASHTO’s formula considers: (4) Materials of construction

19 Dr. Wa'el M. Albawwab SN – The Structural Number for the road profile SN – The Structural Number for the road profile D i – depth of layer i D i – depth of layer i m i – drainage coefficient for layer i m i – drainage coefficient for layer i AASHTO’s formula considers: (4) Materials of construction

20 Dr. Wa'el M. Albawwab Subbase construction materials: layer coefficient a 3 is used to represent the quality of the material AND convert the actual thickness of the subbase to Structural Number (SN, is an engineering term indicative of the total pavement thickness). Subbase construction materials: layer coefficient a 3 is used to represent the quality of the material AND convert the actual thickness of the subbase to Structural Number (SN, is an engineering term indicative of the total pavement thickness). Base construction materials: a2, and Base construction materials: a2, and Surface Course Construction materials: a1. Surface Course Construction materials: a1. AASHTO’s formula considers: (4) Materials of construction

21 Dr. Wa'el M. Albawwab AASHTO’s formula considers: (5) Drainage Purpose: consider the effect of drainage on the performance of flexible pavement Purpose: consider the effect of drainage on the performance of flexible pavement Represented by: m i, i =2,3 (represents the base and subbase layer. Represented by: m i, i =2,3 (represents the base and subbase layer.

22 Dr. Wa'el M. Albawwab AASHTO’s formula considers: (6) Reliability Reliability level: the reliability that the pavement designed will survive for its design period. Reliability level: the reliability that the pavement designed will survive for its design period. E.g., a 50 percent reliability design level implies a 50% chance for successful pavement performance. E.g., a 50 percent reliability design level implies a 50% chance for successful pavement performance. Presented by F R. Presented by F R.

23 Dr. Wa'el M. Albawwab AASHTO’s formula considers: (6) Reliability Z R : Standard normal variation for a given reliability Z R : Standard normal variation for a given reliability S 0 : Estimated overall standard deviation S 0 : Estimated overall standard deviation

24 Dr. Wa'el M. Albawwab Other Issues Drainage Drainage Joints Joints Grooving (noise vs. hydroplaning) Grooving (noise vs. hydroplaning) Rumble strips Rumble strips Climate Climate Level and type of usage Level and type of usage Failure examples are primarily related to design or life- cycle, not construction Failure examples are primarily related to design or life- cycle, not construction

25 Dr. Wa'el M. Albawwab Primary References Mannering, F.L.; Kilareski, W.P. and Washburn, S.S. (2005). Principles of Highway Engineering and Traffic Analysis, Third Edition. Chapter 4 Mannering, F.L.; Kilareski, W.P. and Washburn, S.S. (2005). Principles of Highway Engineering and Traffic Analysis, Third Edition. Chapter 4 Muench, S.T.; Mahoney, J.P. and Pierce, L.M. (2003) The WSDOT Pavement Guide Interactive. WSDOT, Olympia, WA. Muench, S.T.; Mahoney, J.P. and Pierce, L.M. (2003) The WSDOT Pavement Guide Interactive. WSDOT, Olympia, WA. Muench, S.T. (2002) WAPA Asphalt Pavement Guide. WAPA, Seattle, WA. Muench, S.T. (2002) WAPA Asphalt Pavement Guide. WAPA, Seattle, WA.


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