sj-5112 1011 3b horizontal alignment

SJ-5112 Perancangan Geometrik Jalan

Element of Design Sony Sulaksono Wibowo, Ph.D

Element of Design

o Sight Distance

o Horizontal Alignment

o Vertical Alignment

o Cross Section

Horizontal AlignmentConcept of Superelevation and Simple Horizontal Curves

Principles of Highway Alignment

o The alignment of a highway is a three dimensional problem with measurement in x, y, and z dimensions

Principles of Highway Alignment

PROVINSI NADKP2T JALAN/JEMBATAN

HORIZONTAL = 1 : 1000

VERTIKAL = 1 : 100

STA

AN

TO

DA

DA

NG

13NAD2006

STA. 3+403,35 - 4+000

PENAMPANG MEMANJANG JALAN (SEKSI 02)

LEMBAR NOJML LEMBARPROVINSIK P / THNPROYEK

NO

MO

R

ME

MA

NJA

NG

NO

TA

SI

BA

NG

UN

AN

DIP

ER

IKS

A

PA

TO

K-P

AT

OK

DIP

ER

IKS

A

KE

MIR

ING

AN

DIP

ER

IKS

A

DIG

AM

BAR

BU

KU

UK

UR

DIU

KU

R

PO

TO

NG

AN

T

AN

GG

AL

OLE

HP

EK

ER

JAAN

120

PI 1

PI 2

PI 3PI 4

PVI 1

PVI 2PVI 3

PVI 4

3+403,35

9,052 9,052W

2,263 2,263

6 (-)

6 (+)TC CT

- 2 %0 %

6,7896,789

7,784

41,909 41,909W

10,477 10,477

6 (-)

6 (+)TC CT

- 2 %0 %

31,43231,432

34,782

53,633 53,633W

10,477 10,477

6 (-)

6 (+)TC CT

- 2 %0 %

31,43231,432

30,206

21,458 21,458W

5,364 5,364

6 (-)

6 (+)TC CT

- 2 %0 %

16,09316,093

12,122

BRG

MAKAM ISLAM

3+

403.3

5

3+

500

3+550

3+

60

0

3+

65

0

3+700

3+750

3+80

0

3+

85

0

3+

900 3+9

50 4+

000

3+350

3+400

3+

403.3

53+350

3+400

3+

403.3

5

PC

= 3

+500.6

6P

T =

3+516

.20 P

C =

3+564

.65

PT

= 3

+6

31.6

0

PC = 3+775.54

PT

= 3

+8

27

.28

PC

= 3

+8

46

.51

PT

= 3

+8

70.6

3

2

4

6

8

10

12

14

16

18

20

22

24

3+500 3+600 3+700 3+800 3+900 4+000

10.2

86

10.4

44

10.2

33

9.7

88

9.3

82

9.1

53

9.0

62

9.3

33

9.5

42

9.4

95

9.4

05

9.0

44

9.0

00

9.0

00

7 0. 0 00 0 m VC

BV

CS

: 3

+42

5

BV

CE

: 10

.35

3

EV

CS

: 3

+49

5

EV

CE

: 1

0.2

37

10

.38

8

5 0 .0 00 0 m VC

BV

CS

: 3

+6

56

.50

BV

CE

: 9

.20

5

EV

CS

: 3

+70

6.5

0

EV

CE

: 9.1

65

9.1

39

10

.20

5

9.8

86

9.5

66

9.2

47

5 0. 00 0 0 m VC

BV

CS

: 3

+7

64.3

9

BV

CE

: 9.4

42

EV

CS

: 3

+81

4.3

9

EV

CE

: 9.5

01

9.5

21

9.3

74

6 0 .0 0 0 0m VC

BV

CS

: 3

+9

90

BV

CE

: 9.0

73

EV

CS

: 4

+0

50

EV

CE

: 8.9

99

9.0

51

8.9

99

9.4

14

9.2

93

9.1

71

8.9

99

Horizontal Alignment

o Design based on appropriate relationship between design speed and curvature and their relationship with side friction and superelevation

o Along circular path, vehicle attempts to maintain its direction (via inertia)

o Turning the front wheels, side friction and superelevation generate an acceleration to offset inertia


o ‘Components’ of Horizontal Alignment

� Tangents

� Curves � need superelevation

� TransitionsNC

RC


o The critical aspect of horizontal alignment is the horizontal curve that focuses on the design of the directional transition of the roadway in the horizontal plane.

o A horizontal curve provides a transition between the straight (or tangent) sections of roadways.


o The highway engineer must design a horizontal alignment to accommodate a variety of vehicles cornering capabilities that range from nimble sport cars to ponderous trucks.

o Horizontal alignment deals with the positioning, layout, and design of different types of curves and their features (superelevation)


R

Vf

jamkmVdtkmg

gR

VfGf

gR

GV

127

/,/8,9

.

2

2

22

=∴

==

=⇒=

Stadium I:Gaya sentrifugal diimbangi gesekan ban dengan perkerasan sajaG = berat kendaraan; g = percepatan gravitasi


Stadium II:Gaya sentrifugal diimbangi kemiringan melintang jalan

R

Vee

gR

V

e

gR

V

GgR

GV

127

tan

tancos/sin

sincos

22

2

2

=→=

≡≅⇒<<

==

=

ααα

ααα

αα


Stadium III:Gaya sentrifugal diimbangi oleh gaya gesek melintang dan kemiringan melintang jalan

R

Vfeef

gR

V

efgR

V

GGfgR

GV

GGfgR

GV

127

maka ,tan bila ,tan

)cos/(sin

sincoscos

22

2

2

2

=+→+=

=+=

+=

+=

αα

αα

ααα


o if the increases the increases as well

o thus, for a value of V:

feR

V+=

127

2

fe +R

V

127

2

maxmax

min

2

127fe

R

V+=

how to determine superelevation since there are many possibilities of f values?

Side Friction Factor, f

o Representing the lateral acceleration that acts on the vehicle

o Wide variation in vehicle speed � unbalanced force whether the curve is superelevated or not

o The upper limit � point at which the tire would begin to skid (point of impending skid, ‘kondisi dimanaterjadinya slip’)

o Note that highway curves are design to avoid skidding (‘slip’ in Indonesia terminology) condition with a margin of safety

� The f in design should be substantially less than the coeff. of friction at impending skid


o The side friction factor at impending skid depends on a number of factors

� Speed of the vehicle

� Type and condition of the roadway surface

� Type and condition of the vehicle tires

o Study results:

� Max. side friction factors b/w new tires and wet concrete pavements range from about 0.5 at 30 km/h to approx. 0.35 at 100 km/h

� Wet concrete pavements and smooth tires � about 0.35 at 70 km/h

� In all cases, a decrease in friction values as speeds increase


o Key consideration in selecting maximum side friction

� The condition that drivers experiences a feeling of discomfort and reacting instinctively to avoid higher speed

� The speed on a curve (tikungan) at which discomfort emerging could be accepted as a design control for the maximum side friction factor

� Ball-bank indicator:

Various Values of Side Friction, f

Recommended Values of Side Friction, f

Recommended value of fmax is the thick line

o 0,17 for speed of 30 km/jam

o 0.14 for speed of 80 km/jam

o 0.08 for speed of 130 km/jam

Maximum Superelevation, e

o The maximum rates of superelevation (kemiringan permukaanjalan) on highways are controlled by four factors:

� Climate condition, i.e. freq. and amount of snow and ice

� Terrain conditions, i.e. flat, rolling, or mountainous

� Type of area, i.e. rural or urban

� Freq. of very slow-moving vehicles

o Some notes (cited from AASHTO, 2001):

� Suggested value of emax : 4%; 6%; 8%; 10%; 12%

� Common use for highways is emax = 10%

� emax = 12% � where snow and ice do not exist

� emax = 12% � snow and ice exist

� emax = 4% to 6% � traffic congestion or a restriction of top speed

Maximum Superelevation, e

o Other notes:

� Several rates rather than a single rate of maximum superelevation

� A rate of 12% should not be exceeded

� A rate of 4% to 6% is applicable for urban design

� Superelevation may be omitted on low-speed urban streets where severe constraints are present

o Common uses in Indonesia:

� Rural area: emax = 10%

� Urban area: emax = 6%

� In urban built-up areas might not need superelevation

� In toll road design, it is commonly used 8%

Notes on Superelevation

o The minimum rate of cross slope (kemiringanmelintang jalan) applicable to the travelled way id determined by drainage needs

� The minimum values range from 1.5% (high-type surfaces) to 2.0% (low-type surfaces)

o Indonesia:

� Commonly use 2% for all surfaces

� 3% to 4% might be applied on gravel roads (known in Indonesia as ‘Makadam’ or ‘Penetrasi Makadam’)

Minimum Radius, Rmin, of Curvature

o The minimum radius is a limiting value of curvature for a given design speed

o It is determined from maximum rate of superelevation and the maximum side friction factor

o Based on a threshold of driver comfort, rather than safety – why?

o An important control value for determination of superelevation rates for flatter curve – how?

Minimum Radius for Design of Rural Highway, Urban Freeways, and High-Speed Urban Street using Limiting value of e and f

Methods of Distributing e and f

Methods of Distributing e and fo Method 1:

� Superelevation and side friction are directly proportional to the inverse of the radius (i.e. a straight-line relation exists between 1/R = 0 and 1/R = l/Rmin)

o Method 2:

� For sharper curves, f remains equal to fmax and superelevation is then used to sustain lateral acceleration until e reaches emax. In this method, first f and then e are increased in inverse proportion to the radius of curvature.

o Method 3:

� For sharper curves, e remains at emax and side friction is then used to sustain lateral acceleration until, f reaches fmax. In this method, first e and then f are increased in inverse proportion to the radius of curvature.

o Method 4:

� This method is the same as method 3, except that it is based on average running speed instead of design speed.

o Method 5:

� Superelevation and side friction are in a curvilinear relation with the inverse of the radius of the curve, with values between those of methods 1 and 3.

Methods of Distributing

Superelevation and Side Friction

Method 5 Procedure for Development of the Finalized e Distribution

Design Superelevation Rates

Design Superelevation Tables

o Based on Method 5

o Vehicles can travel safely at speeds higher than the design speed on horizontal curves with superelevationrates indicated in the tables

o The use of side friction factors are generally considerably less than can be achieved – why?

o “Normal cross slope” (NC) � curves that are so flat that the elimination of adverse slope is not considered

o “Remove cross slope” (RC) � it is adequate to eliminate the adverse cross slope by superelevating the entire roadway at the normal cross slope

Tangent-to-Curve Transition

o Tangent Runout Section (potongan melintang bagianlurus):

o Superelevation (Curvature) Runout Section (potongan melintang bagian tikungan):

length of roadway is needed to accomplish a change from normal section to rotated section and back to normal section

Superelevation

o Transitions from crowned sections to superelevations sections should be gradual

o Superelevation introduced and removed uniformly over the length of the curve

o To superelevate – rotate about an axis on the cross-section

Superelevation

o Superelevation Transition Distance:

(jarak untuk merubah dari bentuk normal ke superelevasi)

Superelevation – runoff length

o In AASHTO 1994, the runoff length should be at least 2.0 sec. at the design speed

� This criterion gives small superelevation rates

� Problems associated with pavement drainage in the transition section

� Some agencies (among US agencies) do not this control

o AASHTO 2001:

� It is comfortable and aesthetically pleasing runoff design attaining by using maximum relative gradient or suprelevation runoff rate

Superelevation

o Tangent Runout, Lt� Tangent Runoff, Crown Runoff

� Gradual change from normal crowned section to a point where the adverse cross slope is removed

� Adverse cross slope is removed when elevation of outside of pavement is equal to the centerline elevation

� Inside pavement is unchanged

Superelevation - Tangent Runout

Superelevation - Tangent Runout

o Minimum Length of Tangent Runout (AASHTO, 2001)

� eNC: Rate of Normal Cross Slope

� ed: Design Superelevation Rate

� Lr: Minimum Length of Superelevation Runoff

r

d

NCt L

e

eL =

Superelevation

o Superelevation Runoff, Lr� Gradual change from end of tangent runout to a cross section that is fully superelevated

� Rate of transition, Relative Gradient = superelevationrunoff rate (SRR)

Superelevation - Superelevation Runoff


o Minimum Length (AASHTO, 2001)

� w: width of one travel lane, m

� nl: number of lane(s) rotated

� ed: Design Superelevation Rate

� bw: adjustment factor for number of lanes rotated

� ∆: Maximum Relative Gradient or superelevation runoff rate (SRR)

( )( )w

dlr b

ewnL

∆=


o Maximum Relative Gradient


o Adjustment factor for number of lanes rotated, bw:

Superelevation Profile

Two-Lane Highway – Centerline Rotation

Normal Crown

Horizontal

Tangent Runout/Crown Runoff

Superelevation Runoff

Superelevation Achieved

Visual Effect of Having a Spiral Curvebefore a simple horizontal curve

Smooth transition from tangent to curve

The sharp “corners” at the juncture of curve and tangent section may become obvious to from the driver’s seat especially

when the radius is small.

Example:

o A horizontal curve on radius of 800 meters has 3.6 meters lane and crown cross-slope of 0.02 m/m (kemiringan melintang normal, NC, 2%). The design speed is 80 km/h and according to the maximum superelevation of 10%, the required superelevation is 0.043 (4.3%).

o Determine Superelevation Runoff and Tangent Runout for two-lane and four-lane highway.

Answer:

o Data:

� Vdesign = 80 km/h � ∆ = 0.50 (see the previous slide)

� emax = 10%

� eNC = 2%

� ed = 4.3%

� w = 3.6 m

� n1 for two-lane = 1 � bw = 1.00 (see the previous slide)

� n1 for four-lane = 2 � bw = 0.75

o Formula:

� Superelevation Runoff:

� Tangent Runout:

( )( )w

dlr b

ewnL

∆=

r

d

NCt L

e

eL =

Answer:

o Answer:

� Superelevation Runoff:

� two-lane:

� four-lane:

� Tangent Runout:

� two-lane:

� four-lane:

( )( )

( )( ) meters 3196.3000.1

5.0

3.416.3≈=

⋅⋅=

∆= w

dlr b

ewnL

( )( )

( )( ) meters 4644.4675.0

5.0

3.426.3≈=

⋅⋅=

∆= w

dlr b

ewnL

( ) meters 0.144.1496.303.4

0.2≈=== r

d

NCt L

e

eL

( ) meters 0.276.2144.463.4

0.2≈=== r

d

NCt L

e

eL

Tangent-to-Curve Transition

Diagrammatic of Attaining Superevelation

Applying the Superelevation

Simple Horizontal Curves

o Based on how the final superelevation being developed:

� Circular Curves

� Superelevation runoff developed 2/3 on tangent and 1/3 on curve

� Spiral Curves

� The superelevation runoff completely developed on length of spiral

Circular Curve with Spiral (S-C-S)

( )

( )

( )

LsLcL

RpR

Es

kpRTs

sRYcp

sRXck

R

LsLsXc

R

LsYc

Rc

Lc

sc

R

Lss

total 2

2cos

2tan

cos1

sin

40

6

2360

2

2

360

2

2

3

2

+=

−∆

+=

+∆

+=

−−=

−=

−=

=

∆=

−∆=∆

=

θ

θ

π

θ

πθ

Full Spiral Curve (S-S)

( )

( )

( )

LsL

RpR

Es

kpRTs

sRYcp

sRXck

R

LsLsXc

R

LsYc

Lc

c

s

total 2

2cos

2tan

cos1

sin

40

6

0

0

2

3

2

2

1

=

−∆

+=

+∆

+=

−−=

−=

−=

=

=

=∆

∆=

θ

θ

θ

Simple Circular Curve (FC-Full Circle)

∆=

∆=

∆=

∆=

4

1

4

1

0

2

1

tan

tan

2360

tan

TcEc

atau

TcEc

RLc

RTc

πR

O

TCCT

Ec

PI

R

∆∆∆∆

∆∆∆∆/2∆∆∆∆/2

Tc

Lc

Combined Curves

o Combined Curves atau Tikungan gabungan adalah dua atau lebih tikungan yang bersebelahan

o Dapat dibedakan menjadi Tikungan Gabungan Searah dan Tikungan Gabungan Balik Arah

� Tikungan Gabungan Searah yaitu gabungan dua atau lebih tikungan dengan arah putar yang sama

� Tikungan Gabungan Balik Arah yaitu gabungan dua tikungan dengan arah putar yang berbeda.

� Pada dasarnya tikungan gabungan searah kurang disarankan untuk digunakan.

� Penggunaan tikungan gabungan searah pada kondisi khusus dapat diterapkan dengan menyediakan bagian lurus atau spiral diantara dua tikungan yang bersebelahan.

Stationing

Stationing and Stacking Out

o Stationing:

� Straight lines with distances continuous from the beginning to the end of planned road

� Specific station labels are given into vital points on the planned road

� The distances with interval of 50 m or 100 m

� Points of intersection (PI), Points of Vertical Intersection (PVI), Transition points, etc.

� Format of stationing label: X+YYY,ZZZ km

� e.g.12+345,600 means a 12, 345.600 km away from the beginning.

o Stacking Out

� “A drawing” of station points on the land surface

� Locking in reference points � azimuth, distance, GPS coordinates

Stationing for Horizontal and Vertical Alignment


Vertical Alignment

Stasioning

o Jarak A-PI1=d1, PI1-PI2=d2 dan PI2-D=d3

o A = titik awal dan D = titik akhir

o TS – SC = CS – ST = Ls

o SC – CS = Lc

o TS – PI = Ts

A

d1d2

Tikungan 1

Tikungan 2

D

Stasioning:

o Sta A = 1+234,567

o Sta TS1= Sta A + d1– Ts1

o Sta SC1 = Sta TS1 + Ls1

o Sta CS1 = Sta SC1 + Lc1

o Sta ST1 = Sta CS1 + Ls1

1

11

1

1

Pelebaran Perkerasan Jalan di Tikungan

Pelebaran Perkerasan (Jalur) di Tikungan

o Untuk memberikan kebebasan mengemudi di tikungan (jejak kendaraan tetap di dalam tikungan dan dalam lajurnya).

o Besar Lebar total:B = n (b' + C) + (n-1) Td + z

dimana :

n = Jumlah lajur Ialu lintas

b’ = Lebar lintasan truk di tikungan

T = Lebar melintang akibat tonjolan depan

z = Lebar tambahan akibat kelainan pengemudi

C = Kebebasan samping = 0,8 m

o Untuk B ada > B perlu � tidak perlu pelebaran

o Umunya terjadi bila R besar (>1200m) dan atau ∆ kecil (10°)

Pelebaran (Jalur) di Tikungan

Pelebaran di TikunganKebebasan Pandangan

Pandangan Bebas di Tikungan

o Jarak yang diperlukan untuk memenuhi syarat jarak pandang

o Panjangnya tergantung jari-jari (R ), Kecepatan Rencana (V) dan keadaan lapangan.

o Terdapat dua kemungkinan keadaan.


o Jarak pandangan < panjang tikungan;

o S<L):Jarak Pandang > Panjang Tikungan; S>L):

−=

Rπ

S90cos1R

o

M

( )

−+

−=

Rπ

S90sinLS

Rπ

S90cos1RM

o

2

1o

dengan:

R:Jari-jari tikungan (m)

S:Jarak pandang henti (m)

L:Panjang Tikungan (m)

E:Jarak Pandangan Bebas (m)

Length of Superelevation Run Off atau Lengkung Peralihan

Special Notes

Panjang Lengkung Peralihan, LsPanjang Lengkung Transisi, Panjang Lengkung Spiral

o Panjang lengkung peralihan ditetapkan atas pertimbangan bahwa:

� Untuk menghindari kesan perubahan mendadak, nilai Ls dibatasi dan ditetapkan 3 detik dari kecepatan rencana.

� Antisipasi terhadap berangsurnya gaya sentrifugal yang terjadi pada Ls.

� Tingkat perubahan kelandaian melintang jalan (re) dari bentuk enormal

ke e rencana tidak boleh melebihi re-maks

o Tata Perencanaan Geometrik Jalan Antar Kota, Departemen PU, Ditjen Bina Marga, 1997

� untuk kecepatan rencana < 70 km/jam, re-maks = 0,035 m/m/detik

� untuk kecepatan rencana > 80 km/jam, re-maks = 0,025 m/m/detik.


o Percapaian kemiringan

� Panjang jalan yang diperlukan untuk melakukan perubahan superelevasi jalan dari en (normal crown) sampai ep (superelevasi penuh) atau sebaliknya.

o Panjang lengkung peralihan harus:

� Memenuhi kenyamanan dan keamanan pencapaian kemiringan

� Pencapaian kemiringan terjadi secara teratur/seragam

� Tepi perkerasan kelihatan tidak patah-patah (appearance yg bagus)


o Kelandaian relatif, (1/m), yaitu kemiringan tepi perkerasan relatif terhadap sumbu putar perkerasan jalan (sumbu jalan)

o Bila b adalah lebar lajur jalan dan ep adalah superelevasi penuh jalan maka panjang lengkung peralihan adalah:

Lsmin = b . m . e

Panjang Lengkung Peralihan, LsKonsep percapaian kemiringan

ep= h1 /b dan en = h2 /b

h = h1+ h2 = (ep + en).b

Kelandaian relatif, 1/m, = h / Ls

Ls = h.m = (ep + en).b.mMetoda BM - lama

Panjang Lengkung Peralihan, Ls

Dengan konsep percapaian kemiringan

ep= h1 /b dan en = h2 /b

h = h1 = (ep).b

Kelandaian relatif, 1/m, = h / Ls

Ls = h.m = (ep ).b.mMetoda BM - baru

Kelandaian RelatifAASHTO, 2001

Kecepatan Rencana

(km/jam)

Gradient relatif

maksimum (%)

Kelandaian Relatitf

maksimum

20 0,80 1 : 125

30 0,75 1 : 133

40 0,70 1 : 143

50 0,65 1 : 150

60 0,60 1 : 167

70 0,55 1 : 182

80 0,50 1 : 200

90 0,47 1 : 213

100 0,44 1 : 227

110 0,41 1 : 244

120 0,38 1 : 263

130 0,35 1 : 286

Konsep Lengkung Peralihan, Lsmin

AASHTO, 2001

wdl

r benw

L ⋅∆

⋅⋅=

dimana:

w : width of one travel lane, m

nl : number of lane(s) rotated

ed : Design Superelevation Rate

bw : adjustment factor for number of lanes rotated

∆ : Maximum Relative Gradient or

superelevation runoff rate (SRR)

Parameter Perhitungan Lsmin

AASHTO, 2001

Panjang Lengkung Peralihan, LsKonsep Perubahan Percepatan

o Di sepanjang lengkung spiral, Ls, kendaraan mengalami 2 macam perubahan, yaitu:

� perubahan gaya sentrifugal, atau tepatnya percepatan sentrifugal karena massa tetap, dari nol di awal lengkung peralihan menjadi sebesar V2/R di akhir lengkung peralihan

� perubahan kedudukan dari datar (en) di awal lengkung menjadi sebesar superelevasi penuh ep di akhir lengkung peralihan.

Panjang Lengkung Peralihan, LsKonsep Perubahan Percepatan

LsR

V

Ls/V

/RVC

⋅==

32

waktu sepanjang lengkung peralihan: t = Ls/V

percepatan arah radial: V2/R

perubahan percepatan radial terhadap waktu:

atau

CR

V

CR

VLs

⋅=

⋅=

33

021,0

dengan V = kecepatan rencana , km/jam

R = jari-jari busur lingkaran, meter

C = perubahan percepatan, m/det3

Ls = panjang spiral, meter

Shortt Formula: umum digunakan di jalan rel

Panjang Lengkung Peralihan, LsKonsep Perubahan Percepatan dg Pengaruh Kemiringan

Ls

gVk

LsR

V

Ls/V

kg/RVC −

⋅=

⋅−=

32

waktu sepanjang lengkung peralihan: t = Ls/V

percepatan arah radial, dg pengaruh superelevasi:

perubahan percepatan radial terhadap waktu:

atau dg g = 9.81 m/s2

C

Vk

CR

VLs 725,2021,0

3

−⋅

=

V2/R – g.k

k ≡ sin ? dan ? sudut kemiringan

Modified Shortt FormulaUntuk jalan

Panjang Lengkung Peralihan, LsMetode-metode Perhitungan

o Berdasarkan waktu tempuh di lengkung peralihan:

o Berdasarkan perubahan gaya sentrifugal:

TV

Ls r

6,3=

dengan:

Vr = kecepatan rencana (km/jam)

Ls = panjang lengkung peralihan (m)

T = waktu tempuh di Ls, diambil 3 detik

C

eV

CR

VLs rr ⋅

−= 725,2.

021,0

dengan: Vr = kecepatan rencana (km/jam)Ls = panjang lengkung peralihan (m)e = superelevasi penuh

R = jari-jari tikungan (m)C = perubahan percepatan radial (m/s3)

Perubahan Percepatan Radial, C

o Di Amerika nilai C berkisar antara 1,8 - 2,1 m/det3.

o Di Inggris digunakan nilai C = 0,3 m/det.

o Oleh Shortt nilai C dimaksudkan untuk jalan rel tanpa memperhitungkan superelevasi.

o Untuk jalan, digunakan nilai C = 0,6 m/det.

o Rumus Modified Shortt dianjurkan nilai C = 0,4 m/det.


o Berdasarkan tingkat pencapaian perubahan kelandaian

e

rnp

r

VeeLs

⋅

⋅−=

6,3

)(

dengan:

Vr = kecepatan rencana (km/jam)

Ls = panjang lengkung peralihan (m)

ep = superelevasi penuh

en = superelevasi normal (umumnya 2%)

re = tingkat pencapaian perubahan kemiringan melintang jalan,

Vrencana ≤ 70 km/jam re-maks = 0,035 m/m/detik

Vrencana ≥ 80 km/jam re-maks = 0,025 m/m/detik


o Berdasarkan rumus spiral:

o Berdasarkan kelandaian relatif :

RLs s ⋅⋅= θ2 dengan: Ls = lengkung spiral, θs = sudut spiralR = jari-jari tikungan

dengan:

Ls = lengkung spiral,

b = lebar lajur,

m = kelandaian relatif

en = superelevasi normal,

ep = superelevasi penuh.

( )pn eembLs +⋅⋅=

Lengkung Tertajam Tanpa Superelevasi

o Sesuai dengan tipe permukaan, superelevasi normal, enantara 1,5% - 2,0%

o Superelevasi normal ditentukan oleh keperluan drainase permukaan jalan

o Tikungan yang sangat tumpul (radius cukup besar) tidak perlu superelevasi

o Untuk tikungan dengan en

� Mobil di jalur dalam tikungan mempunyai superelevasi positif

� Mobil di jalur luar tikungan mempunyai superelevasi negatif


o Makin tajam lengkungan, makin besar nilai superelevasi.

o Untuk kecepatan yang sama dan radius yang lebih kecil, eneg dan percepatan lateral akan sama dengan nilai f yang timbul

o Hubungan Superelevasi – Kecepatan – Lengkungan digunakan untuk menentukan lengkung minimum yang sudah memerlukan e atau lengkung maksimum dengan en� Untuk tiap kecepatan rencana ditentukan dengan pertimbangan nilai lebih rendah faktor gesekan melintang dengan memperhatikan en dan pergerakan kedua arah lalu-lintas


AASHTO, 2001

end of this part

sj-5112 1011 3b horizontal alignment

Documents