Pavement Analysis and Design

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Pavement Analysis and Design

• Definition
• Pavement
• Pavement is the upper part of roadway, airport
  or parking area structure
• It includes all layers resting on the original
  ground
• It consists of all structural elements or
  layers, including shoulders

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• What is Design?
• Conceived/developed plan for something to serve
  a specific function.
• What is a pavement design?
• It is the process by which the structural
  components a road segment are determined taking
  into account the nature of the subgrade, density
  and traffic composition.

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Functions of the Pavement

• Reduce and distribute the traffic loading so as
  not to damage the subgrade
• Provide vehicle access between two points under
  all-weather conditions
• Provide safe, smooth and comfortable ride to
  road users without undue delays and excessive
  wear tear
• Meet environmental and aesthetics requirement
• Limited noise and air pollution
• Reasonable economy

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Pavement Design Phases

• Highway design consists of three stages
• Geometric design (route selection or alignment
  design)
• Capacity design (number of lanes to meet
  traffic demand)
• Structural design to withstand loads and
  environment
• Structural design consists of 3 steps
• Selection of materials (types of pavement)
• Proportioning of materials
• Layer thickness design

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Requirement of pavement structure

• 1. Sufficient thickness to spread loading to a
  pressure intensity tolerable by subgade
• 2. Sufficiently strong to carry imposed stress
  due to traffic load
• 3. Sufficient thickness to prevent the effect of
  frost susceptible subgade
• 4. Pavement material should be impervious to
  penetration of surface water which could weaken
  subgade and subsequently pavement
• 5. Pavement mat. shd be non-frost susceptible
• 6. Pavement surface shd. be skid resistant

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Types of Pavement Failure

• Failure criteria
• Flexible Pavements
• Fatigue Cracking,
• Rutting,
• Thermal Cracking,
• Rigid Pavements
• Fatigue Cracking,
• Pumping or Erosion
• Others Faulting, spalling, joint deterioration

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Stresses and Strains in Asphalt Pavements
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Stresses and Strains inFlexible Pavements

• Pavement response to applied wheel load
• Stress strain are produced in each layer
• Pavement vertically deflects
• Location and magnitude of responses determine
  type and extent of pavement deterioration and the
  rapidity of deterioration.
• Determined using the theory of elasticity
  (Hooks Law)

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Pavement Responses

• Stresses, Strains, Deflections
• Load-Related
• Vertical
• Shear
• Tensile
• Compression
• Non-Load-Related
• Tensile

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Structural Response Models

• Help determine pavement responses as a function
  of applied load (traffic or environmental)
• Stress, Strain , Deflection

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• Responses are needed for two reasons
• 1. Material characterization, and
• 2. Predicting pavement distress.

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Tension
Compression
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Stresses and Strains Flexible Pavements

• Sources of Stress and Strain
• - Load related
• Vertical Stress and strain (rutting)
• Shear Stresses and strain
• Radial stresses and strain
• Shrinkage stresses and strain (cracking)
• Temperature-Induced Stresses and strains
  (cracking)

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