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Highway Engineering

Mohd Hazri bin Abdan

Amar Ezhar bin Rosli

Rukaine

Engku Nor Hafiza (CE089034)

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Contents1.0 Introduction ............................................................................................................................................... 32.0 Horizontal Curve ........................................................................................................................................ 3

2.1 Design Speed ......................................................................................................................................... 32.2 Design Superelevation .................................................................................................................................. 32.3 Side Friction .................................................................................................................................................. 42.4 Curve Centerline Radius ................................................................................................................................ 42.5 Curve Tangent Length ...................................................... ................................................................. ............ 52.6 Curve Length ................................................................................................................................................. 52.7 The angle subtended by the curve and stations of PI, PC and PT................................................................. 6

3.0 Vertical Curve ............................................................ ................................................................. ....................... 74.0 Cross Section ..................................................................................................................................................... 75.0 Pavement Design .............................................................................................................................................. 7Questions ................................................................................................................................................................ 8APPENDIX ................................................................ .............................................................. .................................. 8

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1.0 Introduction

This project is part of 30% of the assement for the highway engineering course. In this report, there will be 4

short design report, mainly the horizontal curve, the vertical curve, the cross section and the pavement design.

Salam please tambah intro nitak tau nk tulis ape dahhh

2.0 Horizontal Curve

The horizontal alignment of a road is usually a series of straights tangents and circular curves connected by

transition curves. It is the most important elements in road design that affect the safety of the road. The ideal

alignment is that which follows the natural topography as close as possible without any compromise of the

design standards. A circular horizontal curve is designed by determining an appropriate radius that will provide

a smooth flow around the curve. This radius mainly depends on the maximum speed at which the vehicle

transverses the curve and the maximum allowable superelevation.

2.1 Design Speed

The design speed is selected by the designer as a basis for designing the individual geometric design that is the

curves. REAM defined the design speed as a speed selected to establish specific minimum geometric design

elements for a particular section of highway .

In this design project, we select the design speed 80 kph based on the design speed for urban roads (Appendix

1).This design speed falls under the U4 design standards where it provides medium geometric standards and

serve intermediate lengths with medium travelling speeds.

2.2 Design Superelevation

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The superelevation to be adopted is chosen primarily on the basis of safety, but other factors are comfort and

appearance. The superelevation applied to road should take into account

the design speed of the curve, where speed at which the 85 percentile driver is expected to negotiate the length available to introduce necessary superelevation.

In this design project, we choose a maximum superelevation rate of 0.06for urban road areas.

2.3 Side Friction

The side friction (f) is the coefficient of friction between tires and roadway. The maximum permissible

coefficient varies with design speed. From Figure 1, using speed 80 kph , the side friction factor is 0.16. But

According to values of side friction recommended by AASHTO (Appendix 2), the friction factor for design speed

for 80 kph is 0.14 . In this design project, the side friction factor is 0.14

Figure 1: Comparison of side friction factor

2.4 Curve Centerline RadiusMinimum curve radius can be derived to take into account the limit value of superelevation. Equation of

minimum horizontal curve radius depend on the superelevation value is given by American Association of State

Highway and Transportation Officials A Policy on Geometric Design of Highways and Streets (AASHTO Green

Book, 2001) as follows:

R = V2/ 127 (e + f)

= 80 / 127 ( 0.06 + 0.14)

= 251.9 252 m

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2.5 Curve Tangent Length

From Figure 2 of the curve geometry, the following parameters can be determined:

Tangent distance , T = R tan I / 2

External Distance , E = R [ 1 / cos ( /2) 1]

Length of curve , L = R / 180

so the tangent length is , T = 252 tan 70 /2 = 176 m

Figure 2: Horizontal Curve

2.6 Curve Length

Using the following formula, the curve length is

Length of curve , L = R / 180 = 252 x 70 x /180

= 308 m

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2.7 The angle subtended by the curve and stations of PI, PC and PT

From the Figure 3 below, the angle is 70 and the stations of PI, PC and PT are ( 100 + 00), (105 + 50) and (106

+ 182) respectively.

Calculation for station PT = ( 105 +50) + (0 + 308) 176 = ( 106 + 182)

Figure 3:Horizontal curve stations

110

I = 180 110 = 70

PC

PI

PT

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3.0 Vertical Curve

4.0 Cross Section

5.0 Pavement Design

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Questions

1. What is the highest safe speed for which the curve can be designed?

The calculation of safe speed can be calculated by using the following formula, using 0.10 for maximum side

friction ;

Vsafe = ( ) = 252 x 9.81 ( 0.10 + 0.14) x 3.6 = 87.66 kph

APPENDIX

APPENDIX 1

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APPENDIX 2