Bridge Planning

8/9/2019 Bridge Planning

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Bridge Engineering-Planning of Bridges-


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Bridge Planning

1. Traffic Studies

2. Hydrotechnical Studies

3. Geotechnical Studies

4. Environental !onsiderations

". #lternatives for Bridge Ty$e

%. Econoic &easi'ility

(. Bridge Selection and )etailed )esign


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1. Traffic Studies

* i v e r

!ity !enter

+e, Bridge

+e, *oad in

E/isting +et,or

P a

s i g*i v er

!ity !enter


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Traffic Studies

0 Traffic studies need to 'e carried out toascertain the aount of traffic that ,illutilie the New or Widened Bridge

0 This is needed to deterine Econoic

&easi'ility of the Bridge0 So for this Services of a Trans$ortation

Planner and or Traffic Engineer are

*euired0 Such Studies are done ,ith hel$ of TrafficSoft,are such as TransCAD, EMME2 etc.


5/56

Traffic Studies

0 Traffic Studies should $rovide follo,ing

inforation 5 Traffic on Bridge iediately after o$ening

5 To no, the aount of traffic at various ties during

life of the Bridge

5 Traffic 6i/ 7i.e. nu'er of otorcars 'uses heavy

trucs and other vehicles8

5 Effect of the ne, lin on e/isting road net,or

5 Predoinant 9rigin and )estination of traffic that ,illuse the Bridge

5 Strategic i$ortance of the ne,:i$roved Bridge


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2. Hydrotechnical Studies

0 # thorough understanding of the river andriver history is crucial to $lanning of Bridgeover a river

0 Hydrotechnical Studies should include:

1.To$ogra$hic Survey 2 u$strea and2 do,nstrea for sall rivers includingongitudinal section and ;-sections

2. &or 'ig rivers "s


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Hydrotechnical Studies

a8 Scale of the to$ogra$hic a$:!onduct

To$o-Survey 5 12=== for sall rivers

5 1"=== for large rivers

'8 The High &lood evels and the 9'served &lood evel should 'e indicated a$

c8 Sufficient +u'er of /-sections should 'e

taen and H& and 9& ared onthe

d8 *iver Bed surveying ,ould reuire

soundings


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e8 !atchent #rea 6a$

Scale recoended 5 1"==== or

5 12"===

f8 #ll *eservoirs *ainGauges Stns. *iverGauge Stns. should 'eared on a$

Catchment of River Indus


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River Catchment Boundaries with Tributaries


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River Catchment Boundaries with Sub-Basin Boundaries


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3. Hydrological )ata

0 The Hydrological )ata to 'e collected are

1. *ainfall )ata fro *ain Gauge Stations

in the !atchent #rea

2. >sohyetal 6a$ of the !atchent #rea

sho,ing contours of #nnual *ainfall

3. Hydrogra$hs of &loods at *iver Gauge

Stations

4. &lo, ?elocities

". Sedient oad in *iver &lo, during

floods


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Hydrologic )ata

!am"le of an IS#H$T%& '%P


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Hydrologic )ata

!am"le of River Hydrogra"h


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Hydrologic )ata

!am"le of a River Hydrogra"h


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)esign &lood evels

0 ##SHT9 Gives &ollo,ing Guidelines for Estiating

)esign &lood evels


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)esign &lood evels

0 %%SHT# (ives )ollowing (uidelines for stimating

*esign )lood &evels


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)esign &lood evels

0 !#+#)>#+ 6>+>ST*@ 9& T*#+SP9*T#T>9+

Gives &ollo,ing Guidelines for Estiating )esign &lood evels


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)esign &lood evels

0 !#+#)>#+ 6>+>ST*@ 9& T*#+SP9*T#T>9+

Gives &ollo,ing Guidelines for Estiating )esign &lood evels


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)esign &lood evels

0 !#+#)>#+ 6>+>ST*@ 9& T*#+SP9*T#T>9+

Gives &ollo,ing Guidelines for Estiating &ree'oard *euireents

)RB#%R* R+,IR'TS


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Estiating )esign &lood

)lood Pea. *ischarge at Stream or River &ocation

*e"ends u"on:1. !atchent #rea !haracteristics

5 Sie and sha$e of catchent area

5 +ature of catchent soil and vegetation

5 Elevation differences in catchent and 'et,een catchentand 'ridge site location

2. *ainfall !liatic !haracteristics

5 *ainfall intensity duration and its s$atial distri'ution

3. Strea:*iver !haracteristics 5 Slo$e of the river

5 *iver 'ed flo, in the river

5 *iver &acilities: )as on the river


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'ethods of stimating *esign )lood

1. E$irical 6ethods

2. &lood &reuency #nalysis

3. *ational 6ethod


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*ational 6ethod of Pea &lood Estiation

0 #tte$ts to give estiate of )esign )ischarge

taing into account 5 The !atchent !haracteristics

5 *ainfall >ntensity

5 )ischarge !haracteristics of the !atchent

A I C Q T =

A )esign )ischarge

>T #verage rainfall intensity 7in:hr8 for soe recurrence interval T

during that $eriod of tie eual to Tc.Tc Tie of !oncentration

# #rea of the catchent in S. iles

! *unoff coefficientC fraction of runoff e/$ressed as a

diensionless decial fraction that a$$ears as surface runoff

fro the contri'uting drainage area.


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*ational 6ethod of Pea &lood Estiation

0 Tie of !oncentration can 'e estiated using

Barns'y Dillias &orula ,hich is ,idely used'y


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*ational &orula 5 *unoff !oefficient

#rea !haracteristic *un-off !oefficient !

Stee$ Bare *oc =.=Stee$ *oc ,ith Doods =.F=

Plateau ,ith light cover =.(=

)ensely 'uilt-u$ areas =.= 5 =.(=

*esidential areas =.(= 5 =."=

Stiff !layey soils =."=

oa =.4= 5 =.3=

Su'ur's ,ith gardens =.3=Sandy soils =.1 5 =.2=

ungle area =.1= 5 =.2"

Pars a,ns &ields =.2" - =."=


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/0 (eotechnical Studies

(eotechnical Studies should "rovide the

following Information:

1.The ty$es of *ocs )i$s &aults and

&issures

2. Su'soil Ground Dater evel Auality

#rtesian !onditions if any

3. ocation and e/tent of soft layers4. >dentification of hard 'earing strata

". Physical $ro$erties of soil layers


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Geotechnical Studies

!am"le: Cross section of the 1ansas River2 west of Silver &a.e2 1ansas

Ty"ical Borehole


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nvironmental Considerations

1. >$act on &ollo,ing &eatures of Environent need toconsidered 5 *iver Ecology ,hich includes

0 6arine ife

0 Dildlife along river 'ans0 *iver'ed0 &lora and fauna along river 'ans

2. >$act u$on d,ellings along the river if any

3. >$act u$on ur'an environent if the 'ridge in an

ur'an area


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Bridge Econoic &easi'ility


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Bridge Econoic &easi'ility

1. Econoic #nalysis is reuired at&easi'ility Stage to ustify e/$enditures of

$u'lic or $rivate funds

2. # Bridge is the ost e/$ensive $art of aroad trans$ortation net,or

3. Ty$es of Econoic #nalyses

a8 !ost Benefit *atio #nalysis

'8 >nternal *ate of *eturn 7>**8 #nalysis

Bridge conomic %nalysis3


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Bridge conomic %nalysis3&ife Cycle Cost %nalysis 4&CC%5

n-years*esign &ife

C o s t s S t r e a m

B e n e f i t s S t r e a m

C

o n s t r u c t i o n

S

t a g e

Pro6ect &ife P r o 6 e c t S t a r t

* a

t e

n d P r o 6 e c t

& i f e

S a l v a g e

7 a l u e

P t ! t B fit # l i


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Proect !ost Benefit #nalysis

0 The ob6ective of &CC% is to

5 Estiate the costs associated ,ith the Proect during!onstruction an its service life. These include routineaintenance costs I 6aor *eha' !osts

5 Estiate the Benefits that ,ill accrue fro the Proect includingtie savings to road users 'enefits to 'usiness activities etc.

5 Bring do,n the costs and 'enefits to a coon reference $t. intie i.e. ust $rior to start of $roect 7decision aing tie8

5 &acilitate decision aing a'out econoic feasi'ility 'ycalculating uantifia'le yardstics such as Benefit to !ost *atio7B!*8 and >nternal *ate of *eturn 7>**8

0 +ote Salvage ?alue ay 'e taen as a Benefit

This includes cost of the *ight-of-Day and su'structure


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8hat is &ife Cycle Cost9

0 #n econoic analysis $rocedure that uses

engineering in$uts

0 !o$ares co$eting alternativesconsidering all significant costs

0 E/$resses results in euivalent dollars7$resent ,orth8

Ti P i d f % l i


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Time Period of %nalysis

0 +orally eual for all alternatives

0 Should include at least one aor

reha'ilitation

0 +eeded to ca$ture the true econoic

'enefit of each alternative

0 Bridge design today is 'ased on a

$ro'a'ilistic odel of 1== years

Bridge Econoic #nalysis:


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Bridge Econoic #nalysis:ife !ycle !ost #nalysis 7!!#8

C o s

t s S t r e a m

B e

n e f i t s S t r e a m

C

o n s t r u c t i o n

S

t a g e Pro6ect &ife P

r o 6 e c t

S t a r t * a t e

n d

P r o 6 e c t

& i f e

S a l v a g e

7 a l u e

0 Costs and Benefits Change over the life of the Pro6ect

0 %mount of 'oney3Benefit accrued some time in future is worth less interms of Todays money

0 Same is the case with the benefits accrued over time

0 The Problem now is as to How to find the 8orth of a )inancial %mount in)uture in terms of Todays 'oney

0 This is accom"lished by using the instrument of ;*ISC#,T R%T<

Problem:

n-years*esign &ife

Bridge Econoic #nalysis:


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Bridge Econoic #nalysis:ife !ycle !ost #nalysis 7!!#8

*ISC#,T R%T:

The annual effective discount rate is the annual interest divided by the ca"italincluding that interest2 which is the interest rate divided by =>>? "lus theinterest rate0 It is the annual discount factor to be a""lied to the future cashflow2 to find the discount2 subtracted from a future value to find the valueone year earlier0

)or e!am"le2 su""ose there is an investment made of @A and "ays @=>> in a

years time0 The discount rate according the given definition is:

%0.5100

95100=

−== d Rate Discount

%26.595

95100 =−== i Rate Interest

Interest Rate is calculated as @ A as Base

Interest Rate and *iscount Rate are Related as )ollows

2

1

ii

i

id Rate Discount −≈

+

==

)i t * t

http://en.wikipedia.org/wiki/Discount_factorhttp://en.wikipedia.org/wiki/Discount_factor


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)iscount *ate0 Thus )iscount *ate is that rate ,hich can 'e

used to o'tain the Present ?alue of 6oney that

is s$ent or collected in future

et Present value of Cost incurred D Co D 4= - d5n Cn

In $ear n

et Present value of Cost incurred D Bo D 4= - d5n Bn

In $ear n

Time

C o s t s

S t r e a m

B e n e f i t s

S t r e a m

Pro6ect

&ife

P r o 6 e c t

S t a r t * a t e

$ear nCn

Bn

Cost3 Benefit Pro6ectedBac.ward

Bo

Co

Dh t )i t * t t < J


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Dhat )iscount *ate to


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!ost !onsiderations

Maintenance andInspectionCost

Initial Cost

C o s t s

Present Worth

Years

Rehabilitation Cost

Salvage Value

Salvage Costs

! t B fit * ti


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!ost Benefit *atio

&orula for !ost

Benefit *atio

Benefit To Cost Ratio D

∑

∑

−

−

= L

n

L

n

Cnd

Bnd

0

0

)1(

)1(

Costsof ValuePresent

Benefitsof ValuePresent

Dhere ife S$an of the Proect in @ears

d )iscount *ate

Bn Benefit in year n !n !ost incurred in year n

+et Present Dorth: ?al e


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+et Present Dorth: ?alue

0 +et Present Dorth: ?alue +PD or +P?

is defined as follo,s

P8 D P7 D Present 7alue of Benefits E Present 7alue of Costs

ote: If a umber of alternatives are being com"ared2 the alternativethat has the highest et Present 8orth is the "referable one andwill also have the higher Benefit to Cost Ratio

Dhat is >nternal *ate of *eturn 7>**8


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Dhat is >nternal *ate of *eturn 7>**8

0 >** ay 'e defined as that )iscount *ate

at ,hich the Benefit to !ost *atio 7B!*8of a Proect 'ecoes e/actly 1.=

0 >t is a 'etter easure of econoic via'ility

of a $roect co$ared to Benefit to !ost*atio

0 >t is a good indicator of ho, uch inflation

increase and interest rate hie a $roectcan tolerate and still 'e via'le

Present Dorth &actor


42/56

Present Dorth &actor

pwf = Present Worth Factor for discount rate dand year n

d = Discount raten = Number of year when the cost/ benet will

occur

n

d pwf )1( −=

%lternate )ormula 4,sually %do"ted5

( ) nd pwf

+=

1

1

Present Dorth #nalysis


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Present Dorth #nalysis

• Discounts all future costs and benets to the

present:

t=LPW = F ! Σ pwf "#!$!F%!&' ! pwf "(' t=)

PW = Present Worth/ *alue of the Pro+ect F = First ,$nitial- ost

t = .ime Period of nalysis ,ran0es from ) L-# = #aintenance osts$ = $nspection ostsF% = Future %ehabilitation osts

& = &sers osts( = (al1a0e *alues or ostspwf = Present Worth Factor

Tie Period of #nalysis


44/56

Tie Period of #nalysis

0 +orally eual for all alternatives

0 Should include at least one aor reha'ilitation

5 +eeded to ca$ture the true econoic 'enefit of each

alternative

0 Bridge design today is 'ased on a $ro'a'ilistic odel of

1== years

6aintenance !osts


45/56

6aintenance !osts

0 #nnual cost associated ,ith the u$ee$ of the

structure0 >nforation is difficult to o'tain for a given

$roect

0 !ost varies on the 'asis of sie of the structure

7sft80 Best Guess ?alues

5 &reuency: #nnu

5 !oncrete =.=" K of >nitial !ost 5 Structural Steel=.=" K of >nitial !ost

>ns$ection !osts


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>ns$ection !osts

0 Should 'e taen for all alternatives $refera'ly

every t,o years0 !ost varies on the 'asis of sie of the structure

7sft8 and 'y construction aterial

0 Best Guess ?alues 5 &reuency - Biannual

5 !oncrete =.1" K of >nitial !ost

5Structural Steel =.2= K of >nitial !ost

&uture Painting !osts


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&uture Painting !osts

0 9nly a$$lies to structural steel structures

0 Should occur every 2= years

0 !ost varies on the 'asis of sie of the structure

7sft8

0 Best Guess ?alues 5 &reuency 5 every 2= years

5 !oncrete =.= K of >nitial !ost

5 Structural Steel (.= K of >nitial !ost


48/56

&uture *eha'ilitation !osts

0 The freuency is not only a function of tie 'ut also thegro,ing traffic volue and the structural 'ea syste

0 !ost varies on the 'asis of sie of the structure 7sft8 andstructural 'ea syste

0 Best Guess ?alues

5 &reuency

0 &irst occurrence 5 !oncrete 4= years

0 &irst occurrence 5 Structural Steel 3" years

0 #nnual traffic gro,th rate .(" K 7shortens reha'cycles8

5 !oncrete 2=.= K of >nitial !ost

5 Structural Steel 22.= K of >nitial !ost

Salvage ?alue:!osts


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Salvage ?alue:!osts

0 9ccurs once at end of life of structure

0 )ifference 'et,een

5 *eoval cost

5 Salvage value

0 Best (uess 7alues

5 *eoval cost 1= K of >nitial !ost

5 Salvage ?alue 5 !oncrete - = K of >nitial !ost 5 Salvage ?alue 5 Structural Steel - 2 K of >nitial !ost


50/56

Benefits fro a Bridge

6onetary Benefits

0 Tie savings to road users

0 Gro,th in econoic activity0 Saving of ?ehicular ,ear and tear

0 *eduction of accidents if a$$lica'le

E/a$le of Econoic #nalysis


51/56


Carry out an conomic %nalysis of a Pro"osed Bridge given the following *ata:

Estiated #verage #nnualied )aily Traffic is 12=== ?ehicles $er )ay

Dith the &ollo,ing 6i/ of Traffic

!ars 1====

Trucs 1===

Buses 1===

#ssue that the Traffic Gro,th *ate 1.2 K

is Geoetric over the-ife S$an of the Bridge

Bridge -ife S$an F= years

The !onstruction !ost is 2==.= 6illion *s.

s$read over 2 years

The Trade and econoic 'enefits are 1=.= 6illion *s. $er year

estiated to 'e

#nnual Gro,th *ate of Trade Benefits 2.= Kis Geoetric at the rate of over the

-ife S$an of the Bridge

The Bridge ,ould *esult in Tie Saving of 1 hour

to *oad


52/56


#ssue that the Bridge ,ould reuire4

#nnual 6aintenance =.=3 K of !onstruction !ost

6aHor *eha'ilitation after every 3= years 2=.= K of !onstruction !ost

Salvage ?alue of Piers and #'utents 2" K of !onstruction !ost

Salvage !ost is assued to 'e =.= K

#verage 9ccu$ancy 9f a Single !ar 3.= Passengers #verage 9ccu$ancy 9f a Single Truc 2.= Passengers

#verage 9ccu$ancy 9f a Single Bus "= Passengers

Calculate the Present 8orth2 -et Present 8orth2

Benefit to Cost Ratio of the Bridge at *iscount Rate %.= K

Calculate the Internal Rate of Return of the Bridge


53/56



54/56

!am"le of conomic %nalysis



55/56


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56/56


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2=F2 (2 =.=11% %==== %==== ("44=== 24====== 31"44=== %E( 3%%"41 314F4===

2=F3 (3 =.=1=E %==== %==== ("E32== 242===== 31(E32== %"" 34(2(= 31(332==

2=F4 (4 =.=1=3 %==== %==== (%424== 244===== 32=424== %1% 32FEE3 31EF24==

2=F" (" =.==E( %==== %==== (%E1%== 24%===== 322E1%== "(E 311%"F 32231%==

2=F% (% =.==E1 %==== %==== ((4=F== 24F===== 32"4=F== "44 2E"22= 324F=F==

2=F( (( =.==F" %==== %==== ((E==== 2"====== 32(E==== "12 2(E%32 32(3====

2=FF (F =.==F= %==== %==== (F3E2== 2"2===== 33=3E2== 4F1 2%4F"1 32E(E2==

2=FE (E =.==(" %==== %==== (FFF4== 2"4===== 332FF4== 4"2 2"=F3F 3322F4== 2=E= F= =.==(1 %==== %==== (E3(%== 2"%===== 33"3(%== 42" 23(""3 334((%==

2=E1 F1 =.==%( %==== %==== (EF%F== 2"F===== "======= F3(F%F== 3EE ""(F%F F3(2%F==

Total F>F2=>/2=AG FH=2=H2=GF

Total *iscounted Costs D F>F2=>/2=AG Rs0

Total *iscounted Benefits D FH=2=H2=GF Rs0

Present 8orth D F>F2=>/2=AG Rs0

-et Present 8orth D A2/==2AG/ Rs0

Benefit to Cost Ratio D = FA/

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Bridge Planning