CELE Transportation & Highway Engineering — Pavement Design (Flexible and Rigid)Concept Map

Concept

Flexible Pavements

Sub Concepts

• Asphalt Concrete Surface
• Base Layer
• Subbase Layer
• Load Distribution Mechanism
• Rutting Failure
• Fatigue Cracking
• CBR Design Method
• Layer Thickness Design

Relationship To Central

One of two primary pavement types; asphalt-based system distributing loads through layered structure

Concept

Rigid Pavements

Sub Concepts

• Portland Cement Concrete Slab
• Subbase Layer
• Load Spreading by Bending
• Joint Design and Control
• Flexural Stress Analysis
• Modulus of Subgrade Reaction (k)
• Westergaard Analysis
• Slab Thickness Design

Relationship To Central

One of two primary pavement types; concrete slab system using bending to carry loads

Concept

Subgrade Strength Assessment

Sub Concepts

• California Bearing Ratio (CBR)
• CBR Test Procedure
• CBR Interpretation
• Modulus of Subgrade Reaction (k)
• Plate Load Test
• k-value Correlation
• Subgrade Classification

Relationship To Central

Foundation capacity measurement; determines pavement thickness requirements

Concept

Traffic Loading Analysis

Sub Concepts

• Equivalent Single Axle Load (ESAL)
• Load Equivalency Factor (LEF)
• Fourth-Power Law
• Axle Load Classification
• Single Axle
• Tandem Axle
• Tridem Axle
• Design ESAL Accumulation
• Traffic Growth Factors

Relationship To Central

Quantifies cumulative vehicle damage; basis for design life calculations

Concept

Tire-Pavement Interaction

Sub Concepts

• Tire Contact Area Calculation
• Wheel Load (P)
• Tire Inflation Pressure (p)
• Contact Stress Distribution
• Tire Type Considerations
• Dual Wheel vs Single Wheel

Relationship To Central

Interface mechanics determining load transfer and contact pressure distribution

Concept

Design Formulations and Methods

Sub Concepts

• AASHTO Design Guide
• CBR Method (Flexible)
• Structural Number (SN)
• NSCP 2015 Provisions
• Westergaard Theory (Rigid)
• Flexural Strength Requirements
• Design Life Selection
• Reliability and Safety Factors

Relationship To Central

Mathematical frameworks and standards for pavement thickness determination

Concept

Pavement Failure Modes

Sub Concepts

• Flexible Pavement Failures
• Rutting (Permanent Deformation)
• Fatigue Cracking
• Alligator Cracking
• Rigid Pavement Failures
• Flexural Cracking
• Faulting at Joints
• Corner Breaking
• Pumping

Relationship To Central

Mechanisms by which pavements deteriorate under service loads

Concept

Material Properties

Sub Concepts

• Asphalt Binder Properties
• Aggregate Characteristics
• Concrete Compressive Strength (f'c)
• Concrete Flexural Strength (MR)
• Base Course Material Modulus
• Subgrade Resilient Modulus (MR)
• Thermal Properties

Relationship To Central

Physical and mechanical characteristics influencing design decisions

To

CBR Design Method

From

Flexible Pavements

Strength

strong

Relationship

CBR test determines subgrade strength, which directly controls required layer thickness for flexible pavements

To

Modulus of Subgrade Reaction (k)

From

Rigid Pavements

Strength

strong

Relationship

k-value is essential input for Westergaard analysis to compute flexural stresses in rigid slab

To

Load Equivalency Factor (LEF)

From

Traffic Loading Analysis

Strength

strong

Relationship

LEF converts heterogeneous vehicle loads to standard 80 kN single axle equivalents for design ESAL calculation

To

Load Equivalency Factor (LEF)

From

Fourth-Power Law

Strength

strong

Relationship

LEF for single axles follows fourth-power relationship (W/80)^4, showing nonlinear damage accumulation

To

Contact Stress Distribution

From

Tire-Pavement Interaction

Strength

moderate

Relationship

Contact area (A = P/p) and pressure distribution affect stress patterns in pavement layers directly beneath tire

To

Flexible Pavements

From

Design ESAL Accumulation

Strength

strong

Relationship

Total accumulated ESAL over design life is input to structural number (SN) calculation for layer thickness

To

Rigid Pavements

From

Design ESAL Accumulation

Strength

strong

Relationship

Total accumulated ESAL determines flexural fatigue analysis requirement and slab thickness in Westergaard design

To

Flexible Pavements

From

Rutting Failure

Strength

strong

Relationship

Permanent deformation is primary failure mode in flexible pavements under repeated heavy axle loads

To

Flexible Pavements

From

Fatigue Cracking

Strength

strong

Relationship

Flexural fatigue of asphalt and base layers causes alligator cracking failure in flexible pavements

To

Rigid Pavements

From

Flexural Cracking

Strength

strong

Relationship

Tensile stresses exceed concrete flexural strength, initiating cracks perpendicular to load direction in rigid slabs

To

Rigid Pavements

From

Joint Design and Control

Strength

strong

Relationship

Joints control crack location and relieve thermal stresses; critical design element in rigid pavement systems

To

Rigid Pavements

From

Westergaard Analysis

Strength

strong

Relationship

Westergaard theory mathematically models slab bending and stress distribution for rigid pavement design

To

California Bearing Ratio (CBR)

From

Subgrade Strength Assessment

Strength

strong

Relationship

CBR is primary strength parameter for flexible pavement design; correlates to layer modulus

To

Modulus of Subgrade Reaction (k)

From

Subgrade Strength Assessment

Strength

strong

Relationship

k-value quantifies subgrade stiffness from plate load test; essential for rigid pavement design

To

Design Standards

From

NSCP 2015 Provisions

Strength

moderate

Relationship

NSCP 2015 provides Philippine-specific requirements and modifications to pavement design methods

To

Design Standards

From

AASHTO Design Guide

Strength

strong

Relationship

AASHTO is foundational design methodology adopted and adapted in Philippine and international practice

To

Flexible Pavements

From

Structural Number (SN)

Strength

strong

Relationship

SN quantifies structural adequacy; product of layer thickness and material coefficients in flexible design

To

Structural Number (SN)

From

Layer Coefficients

Strength

strong

Relationship

Material-specific coefficients (a1, a2, a3) weight contributions of surface, base, and subbase to SN

To

Flexible Pavements

From

Drainage Factors

Strength

moderate

Relationship

Drainage conditions and moisture affect layer moduli and long-term performance of flexible pavements

To

Rigid Pavements

From

Pumping

Strength

strong

Relationship

Water-induced ejection of fine subgrade material through joints; critical failure mechanism in rigid pavements

To

Rigid Pavements

From

Faulting at Joints

Strength

strong

Relationship

Differential vertical displacement at joints due to erosion and consolidation; limits load transfer and rideability

To

Rigid Pavements

From

Corner Breaking

Strength

moderate

Relationship

Fatigue cracking initiating at slab corners under combined traffic and thermal stresses

To

Rigid Pavements

From

Concrete Flexural Strength (MR)

Strength

strong

Relationship

Modulus of rupture determines maximum allowable flexural stress in slab; critical design input

To

Rigid Pavements

From

Concrete Compressive Strength (f'c)

Strength

moderate

Relationship

Compressive strength correlates to flexural strength and durability; typical requirement 28–35 MPa

To

Flexible Pavements

From

Asphalt Binder Properties

Strength

strong

Relationship

Binder grade (PG or AC) controls temperature susceptibility and fatigue resistance of asphalt layer

To

Material Properties

From

Aggregate Characteristics

Strength

moderate

Relationship

Aggregate size, shape, and gradation affect friction, modulus, and workability in all pavement types

To

Material Properties

From

Subgrade Resilient Modulus (MR)

Strength

moderate

Relationship

Subgrade resilient modulus relates to CBR and affects layer stiffness inputs in flexible design

To

Material Properties

From

Thermal Properties

Strength

weak

Relationship

Temperature-induced expansion/contraction affects joint spacing and stress in rigid; rutting in flexible

To

Traffic Loading Analysis

From

Design Life Selection

Strength

strong

Relationship

Design period (10, 20, 30 years) determines cumulative traffic volume and ESAL target

To

Design Formulations and Methods

From

Reliability and Safety Factors

Strength

moderate

Relationship

Design reliability levels (80–99%) build in safety margins against uncertainties in traffic and materials