Vertical curves can be one of two basic types: crest curves or sag curves.
■
A crest curve exists at a hilltop, or wherever the incoming tangent has a
higher grade than the outgoing tangent. There are three types of crest
curves: a positive to negative grade transition, positive to positive, and
negative to negative. The point of vertical intersection (PVI) of a crest curve
is above the curve.
■
A sag curve exists at the bottom of a valley, or wherever the incoming
tangent has a lower grade than the outgoing tangent. There are three types
of sag curves: a negative to positive grade transition, negative to negative,
and positive to positive. The PVI of a sag curve is below the curve.
The vertical curves on a layout profile can be designed in relation to
engineering speed tables for safe vehicular travel at a particular maximum
speed. Other tables can be used to design vertical curves so that the distance
illuminated by the headlights of a vehicle at night is always greater than the
stopping distance at the maximum design speed.
For more information, see the AutoCAD Civil 3D Help topics Creating Layout
Profiles and Vertical Curve Design.
Exercise 1: Creating a Layout Profile
In this exercise, you will create the layout profile. Typically, this profile is used
to show the elevations along a proposed road surface or a finished grade.
The layout profile is similar to a horizontal alignment, in that it is constructed
of straight tangents with optional curves placed where the tangents intersect.
These tangents and curves on a layout profile are located in the vertical plane
and the intersection points are called points of vertical intersection (PVI).
For more information, see the AutoCAD Civil 3D Help topic Creating Layout
Profiles.
This exercise continues from the
Using Surface Profiles
(page 279) tutorial.
Hide the offset profiles
1
Open Profile-2C.dwg, which is located in the
tutorial drawings folder
(page
819)
.
2
Click the bottom grid to select profile view PV-1. Right-click. Click Profile
View Properties.
288 | Chapter 9 Profiles Tutorials
Summary of Contents for AUTOCAD PLANT 3D 2011 - SYSTEM REQUIREMENTS
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Page 385: ...8 Press Enter Exercise 2 Swinging One End of a Parcel Lot Line 373 ...
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