Course:
TTE 4804/5805—Highway Geometric Design
Homework No.:
Four
Due Date:
Thursday, February 17, 2011
1.
An existing simple horizontal curve is to have spirals added to the ends.
The center portion of
the curve is to remain unshifted.
The curve has the following characteristics:
Degree of curve
5
0
Design speed
50 mph
Length of spiral transition
200 ft
Approximately how much should the tangents be shifted in order to accommodate the spirals?
Hint: spiral offset is the same as p for a spiral.
2.
An existing simple curve has
Δ
= 32
0
12’ 30”,
D
c
= 5
0
and
PC
is at sta. 81+11.40.
It is desired to
realign the curve and put in equal spirals on each end of the curve such that
s
θ
= 6
0
.
Determine:
(a)
the station for the point of intersection,
PI
(b)
the offset distance,
p
(c)
the tangent distance,
T
s
(d)
the distance,
x
s
, for the spiral
(e)
the offset distance, y
s
, for the spiral
(f)
the station for the point of tangent to spiral,
TS
(g)
the station for point of spiral to curve,
SC
(h)
the station for the point of curve to spiral,
CS
(i)
the station for the point of spiral to tangent,
ST
3.
Show on a sketch how to achieve full superelevation (
e
max
) of 10 percent of a 24foot pavement by
revolving the pavement about the centerline.
This is a fourlane divided highway with a design
speed of 60 mph.
The grade of the roadway is 3 percent.
The
TS
is at Sta. 1501+40 at an
elevation of 1,000.00’. The external angle,
Δ
, is 25
0
.
Normal crown is 0.02 ft/ft.
Show edge and
centerline elevations at the
TS
,
SC
, and at Sta. 1535+40.
Also, indicate cross sections at all
major points.
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Repeat Problem 3 by revolving the pavement about the inside edge.
5.
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 Spring '11
 Moses
 design speed, ft/ft

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