{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

Route_alignment_new - 7.1 Introduction CHAPTER 7...

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

View Full Document Right Arrow Icon
7.1 Introduction 7-1 CHAPTER 7 Transportation Route Alignments 7.1 Introduction The famous “Silk Road” has been one of the best known ancient trade routes. This route consisted of many sections, links, and alternates. The “Silk Road” was built as a caravan route connecting China and Western Europe. The route was more than 6,000 kilometers long. First Egyptians, then Romans, and other westerners established trade relationships with China. Far East products (primarily silk, paper, and spices) were transported along this route for many centuries. Caravan “rest areas” were built at distances 30-40 km. from one another. In this way, it was possible to travel between two caravan stations in eight to ten hours on foot. The “Silk Road”, as well as many other ancient and modern roads have ben highly influenced by terrain, and they followed the most convenient path, i.e. the “path of least resistance”. Clearly, the ideal alignment would be a great circle from the point of origin to the point of destination . The most convenient path is usually that one that follows the natural alignment of the countryside. A route alignment represents a defined three-dimensional path. It is usual and convenient to present route alignments in two dimensions: horizontal and vertical alignments . Vertical alignment (also called profile grade line) is composed of a sequence of straight line profiles connected by vertical parabolic curves. In some cases the profile grade increases from a flat alignment. In some other cases, profile grade decreases from a flat alignment. A “ plus grade ” denotes the situation when profile grade is increasing from a flat alignment (Figure 7.1). The opposite situation is known as a “ minus grade (Figure 7.1).
Image of page 1

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

View Full Document Right Arrow Icon
7.1 Introduction 7-2 Figure 7.1 De fi nition of Vertical Pro fi les (Plus Grade and Minus Grade ). Grades are expressed in [%] or in [m/m]. Horizontal alignment represents projection of the alignment onto xy plane (Figure 7.2). Figure 7.2 Horizontal Alignment. The position of a specific point on a highway is traditionally determined using concept of stations . A datum point on a highway alignment is specified. This initial point is designated station 0 + 000.000. The positions of all other points on the highway are calculated by measuring corresponding distances on a horizontal plane along the highway from the initial point. Each station contains one kilometer of highway alignment distance. For example, the point on a highway located 2345.6 m from the previously specified point, is designated station 2 + 345.600. The station 3 + 465.800 corresponds to the highway point located 3465.8 meters from the initial point. + - G 2 G 1 Tangent Tangent Curve Curve G 1 G 2 x y z (0,0,0) Horizontal alignment L L xy
Image of page 2
7.2 Vertical Alignment 7-3 Let us create along horizontal alignment the surface orthogonal to the plane. Let us also denote the distance measured along the horizontal alignment . When we stretch this surface, it becomes flat. We call it plane. The vertical alignment represents the projection of the alignment onto plane (Figure 7.3).
Image of page 3

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

View Full Document Right Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern