16 Horizontal Alignment

8/19/2019 16 Horizontal Alignment

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Horizontal Alignment

CE 453 Lecture 16


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Objectives1. !enti"# curve t#$es an! curve

com$onents

%ee&

'tt$&(()))."')a.!ot.gov(environment("le

*(c'+5.'tm ,C'a$ter 5 "rom -HA/s -le*ibilit# in

Hig')a# 0esign

http://www.fhwa.dot.gov/environment/flex/ch05.htmhttp://www.fhwa.dot.gov/environment/flex/ch05.htmhttp://www.fhwa.dot.gov/environment/flex/ch05.htmhttp://www.fhwa.dot.gov/environment/flex/ch05.htm


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Horizontal Alignment 0esign base! on a$$ro$riate relations'i$ bet)een

!esign s$ee! an! curvature an! t'eir relations'i$

)it' si!e "riction an! su$erelevation Along circular $at' ve'icle un!ergoes centri$etal

acceleration to)ar! center o" curvature ,lateral

acceleration

alance! b# su$erelevation an! )eig't o" ve'icle

,"riction bet)een tire an! roa!)a#


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Horizontal Alignment

1. angents

2. Curves

3. ransitionsCurves reuire su$erelevation ,ne*t lecture

eason "or su$er& ban7ing o" curve retar!

sli!ing allo) more uni"orm s$ee! alsoallow use of smaller radii curves (less

land)


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a!ius Calculation

min 8 999:2 999999 15,e ; "

'ere&

: 8 velocit# ,m$'

e 8 su$erelevation

" 8 "riction ,15 8 gravit# an! unit conversion


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a!ius Calculation<

min relate! to ma*. " an! ma*. e allo)e!< min use ma* e an! ma* " ,!e"ine! b# AA%HO 0O

an! gra$'e! in =reen oo7 an! !esign s$ee!

< f is a "unction o" s$ee! roa!)a# sur"ace )eat'er

con!ition tire con!ition an! base! on com"ort > !rivers bra7e ma7e su!!en lane c'anges an! c'anges )it'in a

lane )'en acceleration aroun! a curve becomes

?uncom"ortable@

<

AA%HO& +.5 2+ m$' )it' ne) tires an! )et $avement to +.35 6+ m$'

< " !ecreases as s$ee! increases ,less tire($avement

contact


7/27 B

a* e Controlle! b# 4 "actors&

Climate con!itions ,amount o" ice an! sno)

errain ,"lat rolling mountainous

#$e o" area ,rural or urban

-reuenc# o" slo) moving ve'icles )'o

mig't be in"luence! b# 'ig' su$erelevation

rates


8/27 D

a* e Hig'est in common use 8 1+ 12 )it' no

ice an! sno) on lo) volume gravelFsur"ace!

roa!s D is logical ma*imum to minimize sli$$ing

b# sto$$e! ve'icles

-or consistenc# use a single rate )it'in a $roject or on a 'ig')a#


9/27 G

%ource& A

Policy on

Geometric

Design of Highways and

Streets ,'e

=reen oo7.

as'ington

0C. American

Association o"

%tate Hig')a#

an!

rans$ortation

O""icials 2++14t' E!.


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a!ius Calculation ,E*am$le

0esign ra!ius e*am$le& assume a ma*imum eo" D an! !esign s$ee! o" 6+ m$' )'at is

t'e minimum ra!ius

" ma* 8 +.12 ,"rom =reen oo7 min 8 999996+2 999999999 9999999

15,+.+D ; +.12

R min = 1200 feet


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-or ema* 8 4 ,urban situation

min 8 999996+2 999999999 9999999

15,+.+4 ; +.12

R min = 1,500 feet


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-or ema* 8 2 ,rotate! cro)n

min 8 999996+2 999999999 9999999

15,+.+2 ; +.12

R min = 1,714 feet


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-or ema* 8 F2 ,normal cro)n a!verse!irection

min 8 999996+2 999999999 9999999

15,F+.+2 ; +.12

R min = 2,400 feet


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Curve #$es

1. %im$le curves )it' s$irals ,)'# s$irals

2. ro7en ac7 > t)o curves same !irection

,avoi!

3. Com$oun! curves& multi$le curves connecte!!irectl# toget'er ,use )it' caution go "rom

large ra!ii to smaller ra!ii an! 'ave ,large I

1.5 ,small

4. everse curves > t)o curves o$$osite !irection

,reuire se$aration t#$icall# "or su$erelevation

attainment


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m$ortant Com$onents o" %im$le

Circular Curve

%ee& "t$&((165.2+6.254.15+(!otmain(!esign(!manual(Englis'(e+2aF+1.$!"

1. %ee 'an!out

2. JC J J E an! ∆

3. L 8 2,π,∆(36+

4. 8 tan ,∆(2

%ource& o)a 0O0esign anual

0 i r e c

t i o n o

" s t a t

i o n i n g

ftp://165.206.254.150/dotmain/design/dmanual/English/e02a-01.pdfftp://165.206.254.150/dotmain/design/dmanual/English/e02a-01.pdf


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%ig't 0istance "or Horizontal Curves Location o" object along c'or! lengt' t'at bloc7s

line o" sig't aroun! t'e curve

m 8 ,1 > cos K2D.65 %

'ere&

m 8 line o" sig't

% 8 sto$$ing sig't !istance

8 ra!ius


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%ig't 0istance E*am$leA 'orizontal curve )it' 8 D++ "t is $art o" a 2Flane

'ig')a# )it' a $oste! s$ee! limit o" 35 m$'.

'at is t'e minimum !istance t'at a large billboar! can be $lace! "rom t'e centerline o" t'einsi!e lane o" t'e curve )it'out re!ucing reuire!%%0 Assume $(r 82.5 an! a 8 11.2 "t(sec2

%%0 8 1.4Bvt ; 999999999v2 9999 3+,99a999 ± =

32.2


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%ig't 0istance E*am$le%%0 8 1.4B,35 m$',2.5 sec ;

99999,35 m$'2 9999 8 246 "eet

3+,9911.2999 ± +

32.2


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%ig't 0istance E*am$lem 8 ,1 > cos K2D.65 %

m 8 D++ ,1 > cos K2D.65 M246N 8 9.43 feet

D++

,in ra!ians not !egrees


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Horizontal Curve E*am$le 0e"lection angle o" a 4 curve is 5525/ J at

station 245;GB.+4. -in! lengt' o" curve an!

station o" J.

0 8 4

∆ 8 5525/ 8 55.41B

0 8 95B2G.5D9 8 95B2G.5D9 8 1432.4 "t

4


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Horizontal Curve E*am$le 0 8 4

∆ 8 55.41B

8 1432.4 "t

L 8 2π ∆ 8 2π,1432.4 "t,55.41B 8 13D5.42"t

36+ 36+


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Horizontal Curve E*am$le 0 8 4

∆ 8 55.41B

8 1432.4 "t

L 8 13D5.42 "t

8 tan ∆ 8 1432.4 "t tan ,55.41B 8 B52.2G "t 2 2


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%tationing E*am$le%tationing goes aroun! 'orizontal curve.

-or $revious e*am$le )'at is station o" J-irst calculate t'e station o" t'e JC&

J 8 245;GB.+4

JC 8 J >

JC 8 245;GB.+4 > B52.2G 8 23D;44.B5


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%tationing E*am$le ,contJC 8 23D;44.B5

L 8 13D5.42 "t%tation at J 8 JC ; L

J 8 23D;44.B5 ; 13D5.42 8 252;3+.1B


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%uggeste! %te$s in Horizontal

0esign1. %elect tangents Js an! general curves ma7ing

sure #ou meet minimum ra!ius criteria

2. %elect s$eci"ic curve ra!ii(s$iral an! calculateim$ortant $oints ,see lab using "ormula or table

,t'ose nee!e! "or !esign $lans an! labreuirements

3. %tation alignment ,as curves are encountere!

4. 0etermine su$er an! runo"" "or curves an! $ut intable ,see ne*t lecture "or !e".

5. A!! in"ormation to $lans

16 Horizontal Alignment

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