Curve 2
11
SETTING OUT OF SIMPLE CURVE Mainly divided into 2 heads: Linear methods High degree of accuracy not required. The curve is short. Angular methods/ Instrument methods Theodolite is used with or without Tape/chain.
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Transcript of Curve 2
SETTING OUT OF SIMPLE CURVE
Mainly divided into 2 heads:Linear methods High degree of accuracy not required. The curve is short.
Angular methods/ Instrument methods Theodolite is used with or without Tape/chain.
Initials of Setting out• Measuring Deflection Angle (∆)• Measuring Tangent Length (T) • Locating PC• Computing Length of the curve (l)• Deciding the Peg Interval • Calculating Chainage of PC• Calculating Chainage of PT• Length of 1st sub chord• Length of Last sub chord• Number of Full chords
Complete Sketch for Elements of Simple Curve
Δ
Δ/2
R
R
E
M
L
l
T T
Δ
PCPT
PIV
V´
A
T1 T2D
C
O
PC PT
d1 DD D D d2
100’
100’ 100’
100’
Sub-chordSub-ch
ord
SETTING OUT OF CURVE
Stationing(usually every 100 feet)
0+00
.00
PIT
1+00
.00
2+00
.00
3+00
.00
4+00
.00
PC
4+
86.7
5
L
5+00
.00
6+00
.007+00.00
PT 7+27.87
8+00.00
9+00.00
10+00.00
11+00.00
PC sta = PI sta – TPT sta = PC sta + L
Linear Methods By ordinates or offsets from long
chord By successive bisection of arcs By offsets from tangents By offsets from chord produced
Instrument Methods Rankins methods of tangential (or
deflection) angleTwo theodolite methodTacheometric method
LOCATION OF TANGENT POINT
Δ
Δ/2R
R
D
Δ
C
E GF
V
O
PI
PC PT
T1T2
ΔVEF and ΔVT1O are similar triangle
VT1/OT1 = VF/EFVT1 = T = (VF/EF)xOT1
As we will be knowing the chainage of V we can locate T1 by deducting T from V.
BY ORDINATE FROM LONG CHORD
O
Δ
Δ/2R
R
D
Δ
C
VPI
PCPT
T1T2
R = Radius of the Curve
Oo= Mid Ordinate
Ox = Ordinate at a dist x from Mid point of the chord
T1 and T2 are Tangent point.
L= T1T2=Length of Long Chord
From ΔODT1
OT12 =DT1
2 + OD2
Or, R2=(L/2)2+(OC-DC)2 = (L/2)2+ (R-O0)2
OO=R - Root {R2-(L/2)}
OX
x
E1
O0
E
FL
Ox=EF=E1D=E1O – DO
Root(EO2 - EE12) - ( CO- DO)
Thus, Ox = Root(R2-x2)-(R-OO)
x
RR
T1
A
V’
E
OX
D
O
RADIAL OFFSETS FROM TANGENT
Ox = Radial Offset at dist x from PC or T1
From Triangle T1DO
DO2=T1O2+T1D2
(DE+EO)2=T1O2+T1D2
(Ox+R)2 = R2+x2
Ox= Root(R2+x2)-R
x
RR
T1
A
V’
E
OX
D
O
PERPENDICULAR OFFSETS FROM TANGENT
Ox = Perpendicular Offset at dist x from PC or T1
T1D=x = E1E
From Triangle EE1O
E1O2 = EO2- E1E2
(T1O - E1O)2 = EO2 - E1E2
(R - Ox)2 = R2 - x2
Ox= R - Root(R2 - x2)
E1
