Highway Engineering

1. أ.د.سعد الحمـراوى أستاذ هندسة الطرق والمطارات أستشارى تصميم المنشآت الخرسانية رئيس قسم هندسة وادارة التشييد Highway Engineering

2. 1-Geometric Design# Introduction# Design Controls and Criteria for Geometric Design# Cross Section Design# Sight Distance# Highway Vertical Alignment# Horizontal Alignment# Design of Highway At-Grade Intersections# Grade Separations- and interchanges Intersections

3. 2- STRUCTURE DESIGN 1- Introduction 2-Soil Engineering of Highways 3-Strength and Density of Soils 4-Pavement Components 5-Highway Materials 6-Flexible Pavement Design 7-Design of Rigid Pavements

4. Teaching and Learning Methods: I- Methods Lectures Laboratory work. Tutorial –problem solving II- Instruments White board presentations Power Point presentations Interactive discussions

5. Schedule: 1- Drop Quizzes Random 2- Solving Assignment Problems Every Week 3- Reports & Presentations & IT applications As per lecturer schedule 4- Practical Works Reports & Exam 13thto 15th Weeks 5- Mid-term written exams 9thWeek 6- Final written exams 16thWeek

8. Procedures Used: I- Class Works: Drop Quizzes. Solving Assignment Problems Reports. Practical Works. II- Written Exams: Mid-term written exams. Final written exams.

9. PART II STRUCTURE DESIGN OF HIGHWAYS

10. The structure design of highway pavements comprises studying soil and paving materials; their behavior under wheel loads, and the design of a pavement to carry that load under all climatic conditions CHAPTER 1INTRODUCTION

11. Right-of-way The right-of-way includes the following: -The roadway (Traffic lanes and shoulders) -Drainage system (ditches, drains, culverts and bridges). Structures such as guard rails, side slopes, retaining walls, road signs, light signals and traffic control devices at intersections. General Definitions:

12. Fig.1: Highway Structure (Right of Way)

13. Two types of pavements are commonly used, flexible- and rigid pavements as shown in Figure 2 1-Flexible Pavement: Flexible pavements consist of a layered system in which wheel load effects are progressively reduced with depth. The flexible pavement structure consists of three layers, wearing course, base course and subbase. Under subbase laying the subgrade soil. Pavement Types

15. 2.Rigid Pavement:Rigid pavements have relatively high resistance to bending such as Portland cements concrete pavements. The essential difference between the two types of pavements, is the manner in which they distribute the loads over the subgrade. High modules of elasticity for rigid pavement tend 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

17. 1) Surface course: It is the top layer of the pavement directly in contact with traffic and has the following functions: 1. It acts as a wearing surface which resists the abrasion and direct traffic effects and pressure. 2. It transmits the wheel loads to the base and subgrade without cracking or disintegration. 3. It reduces the tractive resistance of traffic. 4. It protects the base course from the action of water and climatic affect. Structural Components of Pavements

18. 2-Base Course: It is a layer of high quality material below the wearing course through which the wheel loads are transmitted to the subgrade soil or subbase. The main functions of base course are: 1.It acts as a foundation to the top surface course; 2. It distributes the wheel load into a greater area; 3. It protects the surface course against the volume changes of clay subgrades; 4. It prevents the capillary rise.

19. Base courses are used under rigid pavements for various reasons as: • 1. control of pumping; • 2. control of frost action; • 3.drainage; • 4.control of the subgrade swelling.

20. 3- Subbase Course: It is a layer of material may be used between base course and subgrade. The functions of subbase are: 1-It drains the water and prevents the rise of capillary water, and subsequently protects the base course against the volume changes of subgrade.

21. 2. In soft clay subgrades, a sand or stabilized soil subbase must be used to prevent the working of clay subgrade into the voids of the crushed stone or gravel above it. • 3. It transmits the wheel load to subgrade and protect it against frost action in freezing weather. • Subbase are usually from granular materials as gravel, sand, crushed stones, and stabilized soil.

22. 4- Subgrade The subgrade is the top layer of embankment in fill soil or the top portion in the cut over which the pavement are placed. It has a depth of 30-50 cm and acts as the foundation, and must be compacted to max. dry density by artificial means of compaction.

23. 1.The wheel load, W, is transmitted to the surface of pavement through the tire as a uniform vertical pressurePo . The stresses are spread through the pavement structure to producea reduced vertical stress, P1 at the base surface, P2 at the subbase surface and P3 at the subgrade surface 2.The deflection in pavement structure leads to creating compressive and tensile stresses

26. The primary loading factors in flexible pavement design are: 1. Amount of axle (and wheel) loads; 2. Volume and composition of axle loads; 3. Tire pressure and contact area. 1.2. Traffic Loading:

27. 1. single and dual wheels; 2. single and tandem axles. 1.2.1. Wheel Loads

29. The asphalt Institute and also the AASHO recommend that the effects of traffic on structural design of the pavement be expressed in terms of the number equivalent single axle loads (ESAL). 1.2.2.Volume and Composition of axle loads:

30. The radius of contact area is as follows: a =  P/Pt .  where: a = radius of contact area; P = total tire load, Pt= contact pressure. 3.Tire Pressure and Contact Area: