{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

chapter4_notes_

# chapter4_notes_ - Chapter 4 Pavement Design 1.1...

This preview shows pages 1–4. Sign up to view the full content.

Chapter 4 Pavement Design 1.1 INTRODUCTION Over 3 million miles (4.8 million kilometers) of highways in US (55% are paved). Several states (Pennsylvania, Texas, Illinois, and California) have pavement construction and rehabilitation budgets that exceed a billion dollars per year 1.2 PAVEMENT TYPES Why pavements? Typical soil-bearing capacities can be less than 50 lb/in 2 (345 kPa) and in some cases as low as 2 to 3 lb/in 2 (14 to 21 kPa). Typical automobile weighs approximately 2700 lb (12 kN), with tire pressures of 35 lb/in 2 (241 kPa). Typical tractor semi-trailer truck that can weigh up to 80,000 lb (355.8 kN), the legal limit in many states, on five axles with tire pressures of 100 lb/in 2 (690 kPa) or higher. 1.2.1 Flexible Pavements Figure 4.1 Typical flexible-pavement cross section. Components: Top layer made of asphaltic concrete, which is a mixture of asphalt cement and aggregates. The purpose of the wearing layer: Protect the base layer from wheel abrasion and to waterproof the entire pavement structure. Provides a skid-resistant surface for vehicle performance. Other layers (Fig. 4.1) – thicknesses vary with the type of axle loading, available materials, and expected pavement design life. 1.2.2 Rigid Pavements Rigid pavement is constructed with Portland cement concrete (PCC) and aggregates: Figure 4.2 Typical rigid-pavement cross section. 1.3 PAVEMENT SYSTEM DESIGN: PRINCIPLES FOR FLEXIBLE PAVEMENTS Assumed load distribution: Figure 4.3 Distribution of load on a flexible pavement.

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
A and B = function values, as presented in Table 4.1, that depend on z/a and r/a , the depth in radii and offset distance in radii, respectively, Where: z = depth of the point in question in inches (mm), r = radial distance in inches (mm) from the centerline of the point load to the point in question, and a = equivalent load radius of the tire footprint in inches (mm).

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### Page1 / 14

chapter4_notes_ - Chapter 4 Pavement Design 1.1...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online