De6202 Highway Engineering 2 Assessment Answer

Problem 1

The general form of the parabolic equation, as applied to vertical curves, i

y=ax^2+bx+c

Where 

y= roadway elevation at station distance x from the beginning of the vertical curve

x= station distance from the beginning of the vertical curve

c= elevation of the Point of Vertical Curve(PVC)

Show that the parabolic vertical curve provides a constant rate of change in slope;

Let G_1 be the initial roadway grade, and G_2 be the final roadway grade, and L be the length of the curve measured in a constant-elevation horizontal plane. Express  a and b as functions of G_1,G_2, and L.Calculate offsets at PVI and at PVT.Show that the parabolic vertical curve implies equal curve tangents, i.e., the station distance from the Point of Vertical Intersection (PVI) to the PVC equals the station distance from the Point of Vertical Tangent (PVT) to the PVI. 

Problem 2

Using NZTA State Highway Geometric Design Manual you are required to design road realignment (see figures below). 

The station value at the start of the transition curve (TS) is 5100m and the PVC (of the vertical curve) is at station 5135m (51+35). The elevation at the PVC is 25.050m.

The design should include:

horizontal curve calculations, where R=700m, SL(or Lp) =100m 

check R > R(min), find I, edes(%), P, Lc(length of curve), Lcr, K, TT, ET. 

superelevation design at key points along the curve and every 20m. Superelevation should be presented in a table with station values. 

the vertical curve calculations including low point and finish levels at 20m intervals. The vertical curve proposed length L is 650m (check against minimum requirements).

The design should show all calculations including references to tables used from SHGDM.