Lecture 2 (CE-860).ppt
Download as PPT, PDF0 likes109 views
This document provides an overview of pavement design and analysis. It describes the two main types of pavements - flexible and rigid. Flexible pavements use asphalt and distribute loads through layered systems, while rigid pavements use concrete and distribute loads through slab bending. The document outlines the typical components and structures of each pavement type. It also discusses serviceability measures and causes of pavement distress.
Lecture 2 (CE-860).ppt
- 2. PAVEMENT DESIGN AND ANALYSIS (CE-860) LEC-02 Fall Semester 2017 Dr. Arshad Hussain arshad_nit@yahoo.com , Office Room#111, Tel: 05190854163, Cell: 03419756251 National Institute of Transportation (NIT) School of Civil & Environmental Engineering (SCEE) National University of Science and Technology (NUST) NUST Campus, Sector H-12, Islamabad
- 3. PAVEMENT TYPES Flexible Pavements Rigid Pavements
- 4. FLEXIBLE PAVEMENT Based on Structural Response flexible pavements normally use asphaltic concrete (AC) as the surface, and sometimes underlying layers. Flexible pavements are made of a series of layers with the strongest material layers at or near the surface.
- 5. FLEXIBLE PAVEMENT The load-carrying capacity of flexible pavements is brought about by the load-distributing characteristics of the layered system, thereby, distributing the load over the subgrade, rather than by the bending action of the slab.
- 6. FLEXIBLE PAVEMENT Structure ◦ Surface course ◦ Base course ◦ Subbase course ◦ Subgrade
- 7. COMPONENTS OF FLEXIBLE PAVEMENT Seal Coat Surface Course Binder Course Base Course Subbase Course Compacted Subgrade Natural Subgrade
- 9. RIGID PAVEMENT Rigid pavements are made up of Portland Cement Concrete and may or may not have a base course between the pavement and the subgrade. The rigid pavement, because of its rigidity and high modulus of elasticity, tends to distribute the load over a relatively wide area of soil; thus, a major portion of the structure capacity is supplied by the slab itself.
- 10. RIGID PAVEMENT The major factor considered for the design of rigid pavements is the structural strength of concrete. Minor variations in the subgrade strength have little influence on the structural Capacity of Concrete Pavements.
- 11. RIGID PAVEMENT Base course are provided under rigid pavements for various reasons: Control of Pumping Control of Frost Action Drainage Control of Shrinkage & Swell potential of the subgrade Construction facilitation
- 13. RIGID PAVEMENT Provision of Base/Subbase Course lends some structural capacity to the pavement. However, its contribution to the load carrying capacity may be relatively minor. Load Carrying Capacity of rigid pavements is due to BENDING of slabs.
- 14. RIGID PAVEMENT Structure ◦ Surface course ◦ Base course ◦ Subbase course ◦ Subgrade
- 15. COMPONENTS OF RIGID PAVEMENT PCC Slab Granular Base/Subbase Layer Subgrade
- 16. HIGHWAY AND AIRFIELD PAVEMENTS Highways are generally 24 feet wide Runways are 150 feet wide Taxiways 75 feet wide Runways are always crowned, whereas, highways may or may not. Taxiways and runway ends are constructed using thicker section than the central portion, due to high concentration of traffic.
- 17. HIGHWAY AND AIRFIELD PAVEMENTS Rigid Highways, if without base/subbase layer, due to heavy distresses always show pumping. Airfield pavements comparatively show less pumping. Highways; more distresses at the edge of the pavement. Airfield pavements do not show edge distresses.
- 18. HIGHWAY AND AIRFIELD PAVEMENTS Major differences are repetition of load, distribution of traffic and geometry of pavement. For a given wheel load and tire pressure, Highway Pavements are thicker than Airfield Pavements. Due to high repetition of load on highway pavements and due to close application to the edges.
- 19. HIGHWAY AND AIRFIELD PAVEMENTS However, as the gross weight of aircraft is very high with the result that airfield pavements are actually thicker in practice.
- 20. FRAMEWORK OF PAVEMENT DESIGN TYPES OF FAILURES Structural Failure Functional Failure
- 21. STRUCTURAL FAILURE Collapse or a breakdown of one or more of the pavement components of such magnitude to make the pavement incapable of sustaining loads imposed on the surface.
- 22. FUNCTIONAL FAILURE May or may not include structural failure, however, the pavement will not carry out its intended function without causing distress and discomfort to passengers or high stresses to the vehicle due to surface roughness.
- 23. CAUSES OF DISTRESS Overloading High load repetitions High tire pressure Climatic and environmental conditions Freeze-Thaw or Dry-Wet
- 24. SERVICEABILITY Serviceability is used to describe how “GOOD” a pavement is. Developed during AASHTO Road Tests. Present Serviceability Index (PSI) Used as a measure of serviceability. Rating scale 0 to 5. PSI = 5 – Perfect pavement PSI = 0 – Imperfect pavement Done by a panel of individuals. Based on objective measurements made on pavement surface.
- 25. SERVICEABILITY Longitudinal Roughness. Amount of Cracking and Patching. Rut Depth for Flexible Pavements.
- 26. PSI EQUATION For Flexible Pavement PSI = 5.03 - 1.9 log(1+SV) - 0.01√(C+P) – 1.38(RD)² For Rigid Pavement PSI = 5.41-1.8 log(1+SV)-0.09√(C+P)
- 27. ABBREVIATIONS PSI – Pavement serviceability index C – Linear feet of cracking per 1000 sq feet area P – Bituminous patching in sq ft / 1000 sq ft area SV – Slope Variance RD – Rut Depth in inches (both wheel tracks) measured with 4 feet straight edge
- 28. AGENCY ABBREVIATIONS AASHTO – American Association of State Highway and Transportation Officials FAA – Federal Aviation Administration AI – Asphalt Institute TRL – Transportation Research Laboratory ARRB – Australian Road Research Board FHWA – Federal Highway Administration
- 29. AGENCY ABBREVIATIONS NCHRP – National Cooperative Highway Research Program TRB – Transportation Research Board NHA – National Highway Authority NTRC – National Transportation Research Centre ASTM – American Standards for Testing Materials BSS – British Standard Specifications ACI – American Concrete Institute
- 30. Thanks