Chap 3 Curve PDF

UNIT THREE CURVE 3.1 General Introduction to Curve Route Surveying includes all the surveying & mapping activates (the field and office work) required to plan, design, and layout (construct) and any "Long and narrow" transportation facility. This transportation facility could be road (high way), ra...

UNIT THREE CURVE 3.1 General Introduction to Curve Route Surveying includes all the surveying & mapping activates (the field and office work) required to plan, design, and layout (construct) and any "Long and narrow" transportation facility. This transportation facility could be road (high way), railways, pipeline, and power transmission lines. The "Shape" or geometry of any transportation route is called its alignment. This includes both its horizontal alignment (i.e. a plan view), and its vertical alignment (i.e., a profile view). The vertical alignment is also called the grade line. The centerline of highway, railroad, or canal consists of series of straight lines, (tangents) connected by curves for safe and Bearing of the Geometric data for each horizontal comfortable ride. The plan view should tangents Angle of curve Topography adjacent to the include: intersection center line Existing structures Stationing The vertical affected by connected alignment consists of straights (gradients) the projectby vertical curves in a vertical plane. The profile view should tations (chainages) include: The existing Location of drainage structures ground surface Proposed Elevations of existing ground surface & route grade line Grades proposed grade lines (slopes) of the tangents Vertical curve data 1 3.2 Types of Curves and Their Uses Curves are provided in the line of communication like roads, railways, canals etc. to bring about the change of direction gradually. The two types of curves are horizontal curve and vertical curve. Fig. 3- 1: Types of Curves Horizontal Curve Horizontal curves are curves that are used to connect straight line called tangent in horizontal plane. The curves employed normally are circular although spiral curves may be used to provide gradual transitions to or from the circular curves. Their design & their construction are considered in the horizontal plane. The sharpness of circular curve may be described by their radius (R) or their degree of curve (D0). Therefore curves are designated either by either of them. E.g. a 750m curve or a 20 curve The followings are the types of horizontal curve 3.3 Simple Circular Curve A Simple Curve is a circular arc joining two intersecting tangents. The radius of the circle determines the sharpness or flatness of the curve. Elements of the simple circular curve Vertex (V) - the point of intersection (PI) of two intersecting tangents. Point of curvature (PC) - the point of tangency where the curve leaves the tangent. Point of tangency (PT) - the point of tangency where the curve meat the other tangent. Tangent distance (T) - the distance from the vertex to the PC or PT. Intersection angle (I) or Δ- the angle by which the forward tangent deflects from the back tangent Radius (R) - the radius of the circle of which the curve is made. External distance (E) is the distance from the vertex to the mid- point of the circular curve. Long chord (C) - is the distance from the point of curvature (PC) to the point of tangency (PT).  Only two pages were converted. Please Sign Up to convert the full document. www.freepdfconvert.com/membership