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Case History Analysis of Bridge Failures due to Scour

Cheng Lin1, Jie Han2,Caroline Bennett3, and Robert L. Parsons4

1Project Geotechnical Engineer, Ph.D., Terracon Consultants, nc., !!"1 Ro#land $%e., &a%annah, G$

'1("()clin*terracon.co+!Proessor, Ph.D., P.E., -ni%ersit o /ansas, CE$E De0art+ent, La#rence, /& "(2)

jiehan*3u.edu'$ssociate Proessor, Ph.D., P.E., -ni%ersit o /ansas, CE$E De0art+ent, La#rence, /& "(2)

crb*3u.edu(Proessor, Ph.D., P.E., -ni%ersit o /ansas, CE$E De0art+ent, La#rence, /& "(2)r0arsons*3u.edu

ABSTRACT: &cour is a +ajor cause or bridge ailure. To understand thecharacteristics o bridge ailures under scour conditions and 0ro%ide useul

inor+ation or scour counter+easure, this stud re%ie#ed and anal4ed totall

' historical cases o bridge ailure due to scour, including their hdraulic,geotechnical, and structural conditions and ailure +odes. Based on the collected

data, +ost o scour de0ths 5i.e. u0 to (167 ranged ro+ ".2 to 2 +, but the

+a8i+u+ scour de0th could be u0 to 12 +. Local scour #as accounted or (6bridge ailures, ollo#ed b channel +igration 51(67, and contraction scour

5267. Possible bridge ailure +odes due to scour included %ertical ailure, lateralailure, torsional ailure, and bridge dec3 ailure. $00ro8i+atel 9"6 o bridge

ailures #ere lateral and %ertical. The indings ro+ this stud can be u0dated#hen +ore cases o bridge ailure under scour conditions are collected and:or

beco+e a%ailable.

INTRODUCTION

&cour re+o%es soils around bridge oundations b lo#ing #ater, and thus reducesthe ca0acit o bridge oundations. &cour e%ents can cause da+ages to bridges thus

0osing a 0otential threat to 0ublic saet. $ccording to Lagasse et al. 5!""97, "6

bridge ailures in the -nited &tates resulted ro+ scour.To +ini+i4e bridge ailures, the ;ederal High#a $d+inistration 5;Hsusce0tible. This stud intended to characteri4e

bridge ailures due to scour based on the collected case histories. The bridge ailuresunder scour conditions can result ro+ co+bined actors including hdraulic,

geotechnical, and structural conditions. $nalsis o these actors #ill hel0 understand

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characteristics o bridge ailure due to scour and 0ro%ide useul inor+ation or

selection o a00ro0riate scour counter+easures.

n this stud, ' cases o bridge ailures 0ertaining to scour #ere collected and theirhdraulic, structural, and geotechnical conditions #ere anal4ed. The collected case

histories include !" ro+ ?e# @ealand, 1( ro+ the -&$, and ! ro+ Canada. t

should be 0ointed out that scour characteristics and 0ossible da+ages highl de0endon geological and cli+atic conditions. The conditions in other countries +a be

dierent ro+ those anal4ed in this stud. The results ro+ this stud #ill be

u0dated #hen +ore cases o bridge ailures due to scour are collected and:or beco+ea%ailable. This 0a0er irst re%ie#s t#o classical cases 5i.e. ailures o the &choharie

Cree3 Bridge and the Hatchie Ri%er Bridge7, and then anal4es the conditions or

bridge ailure and bridge ailure +odes in the scour e%ents. This 0a0er also briel

su++ari4es the re+ediation +easures against scour da+age.

FAILURS OF TH SCHOHARI CR! BRID" AND TH HATCHI

RI#R BRID"

;ailures o the &choharie Cree3 Bridge in the ?e# Aor3 &tate and the Hatchie Ri%er

Bridge in Tennessee ha%e been #idel 3no#n in the scour histor and ha%e beenconsidered a dri%ing orce +oti%ating e8tensi%e scour research in the -nited &tates.

These t#o cases are thus discussed belo# in detail.

Failure of t$e Sc$o$arie Cree% Bridge

The &choharie Cree3 Bridge colla0sed in 19, lea%ing 1" 0eo0le dead. This

bridge had t#o s0ans o%er the &choharie Cree3 near $+sterda+, ?e# Aor3. Thebridge suered se%ere scour ater a s0ring lood, #hich caused colla0se o Pier ' and

subse=uent &0ans ' and ( 5&tore and Delatte !""'7. The 2">ear lood e%ent #ith a

%elocit o (. +:s #as a result o a co+bination o hea% rainall and sno#+elt


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utili4ed) the lightl reinorced concrete 0iers had li+ited ductilit) and deicient 0linth

reinorce+ent resulted in sudden crac3ing o the 0linth instead o a hinging ailure.

Failure of t$e Hatc$ie Ri&er Bridge

The Hatchie Ri%er Bridge near Co%ington, Tennessee ailed in 1. The ailure3illed nine %ehicle occu0ants. The bridge colla0sed during a lood e%ent) the ailure

#as characteri4ed b the colla0se o t#o adjacent 0ile>su00orted southbound colu+n

bents. &cour e80osed riction 0iles under one colu+n bent to #ater or a de0th o '+eters, resulting in the 0iles losing ca0acit to su00ort the bent. The ailure o the

bridge #as 0rogressi%e ro+ s0an settle+ent to co+0lete s0an colla0se #ithin a ti+e

s0an o (2 +inutes. $s %ehicles 0assed o%er the s0ans su00orted b one o the

distressed colu+n bents 5Bent 9"7, the bent began to settle and leaned north#ard. naddition to the orces induced b the sliding o the hea% su0erstructure ele+ents 5u0

to 9 tons7, lateral and %ertical loads #ere added to Bent 9", resulting in continuous

settle+ent and buc3ling o the riction 0iles. Later orensic in%estigation re%ealed

that the 0iles deteriorated ater being e80osed to #ater o%er a 0rolonged 0eriod oti+e. $ !26 reduction in the 0ile dia+eter #as noted) this #as h0othesi4ed to be

another 0ri+ar reason or buc3ling ailure 5?T&B 1") Tho+0son 1") Jac3son etal. 117.

t #as deter+ined that a co+bination o channel +igration and local scour directl

contributed to the colla0se o the Hatchie Ri%er Bridge. Ho#e%er, insuicientins0ection #as a hu+an actor res0onsible or the bridge ailure. &cour ins0ection

had not reached the lo#est le%el o the ri%erbed at the ti+e beore the colla0se. n

addition, e%aluators ailed to recogni4e the i+0ortance o the e80osure o the riction

0iles. t is #ell 3no#n that riction 0iles are de0endent on the surrounding soils toattain %ertical ca0acit. ;urther+ore, a %ariet o o%er#eight truc3s 0er+itted to

tra%el across the bridge +ight ha%e aggra%ated the colla0se o the Hatchie Ri%er

Bridge.

CONDITIONS ASSOCIATD 'ITH SCOUR(INDUCD BRID" FAILURS

Bridge scour is a co+0le8 0rocess in%ol%ing the interactions a+ong lo#ing #ater,

soils, and bridge structures. Thus, scour>induced bridge ailures are associated #ith

hdraulic, geotechnical, and structural conditions.

Hydraulic condition

Hdraulic condition consists o scour t0es, scour de0ths, and lo# characteristics.n general, bridge scour includes local scour, contraction scour, general scour, and

channel +igration. Local scour occurs around the bridge 0ier or oundation.

Contraction scour is due to the contraction o lo# area #hen the lo# encountersobstruction. Contraction scour t0icall de%elo0s across the entire channel section.

General scour reers to the long>ter+ scouring o ri%erbed e%en #ithout the e8isting

obstruction such as bridges. Channel +igration is a long>ter+ erosion o ri%er ban3s

due to the lo# tendenc to +igrate laterall.

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$ bridge +a ail due to a co+bination o dierent scour t0es) ho#e%er, one scour

t0e is oten the +ajor cause to the bridge ailure. $s such, the case histor analsis

onl associated the bridge ailure #ith one scour t0e. Table 1 su++ari4es thedistribution o scour t0es a+ong scour>induced bridge ailures. Table 1 sho#s that

local scour is the do+inant scour t0e a+ong all the bridge ailure cases e8a+ined in

this stud 5accounted or a00ro8i+atel (6 bridge ailures7. The second do+inantscour t0e is channel +igration, #hich resulted in a00ro8i+atel 1(6 bridge ailures.

n contrast, contraction and general scour occurred less re=uentl.

Table ! gi%es the range o scour de0th obser%ed at %arious bridges at ailure. &courde0th #as not al#as +easured during or ater bridge ailures. nl !! cases o

bridge ailures re0orted the scour de0ths. Table ! sho#s that the scour de0th ranged

ro+ ".2 to 12 +. $ shallo# scour de0th o ".2 to !." + #as accounted or 16 o

the ' bridge ailures. n these 0rojects, bridges #ere +ostl su00orted b shallo#oundations. Ho#e%er, +ost o bridge ailures 5!26 o total ' cases7 occurred at the

scour de0th ranging bet#een !." and 2." +. Bridge ailures also occurred at greater

scour de0ths but less re=uentl.

Ta)le *+ Scour Ty,es and Nu-)er of Bridge Failures

Ty,es of scour Nu-)er .ercentage

Local scour !' (6

Contraction scour ! 26

General scour 1 '6

Channel +igration 2 1(6

?ot deter+ined 2 1(6

Total ' 1""6

&cour da+age oten e8acerbates #hen lood occurs. High strea+ %elocit causedb lood tends to increase scour de0th around bridge oundation. $s a result,

$$&HT 5!""97 re=uires that bridge scour should be in%estigated under loodconditions, i.e. design lood 51"">ear lood7 and chec3 lood 52"">ear lood7.

;loods are oten acco+0anied b debris such as drits, logs, and other debris along

the ri%er. $ccu+ulation o debris around the bridge li3el directs #ater do#n#ardand thus increases the scour de0th. $lso, debris accu+ulation increases lateral loads

to bridges, and thereore increases the 0ossibilit o bridge ailures. ;igure 1 sho#s

that 926 o scour>induced bridge ailures #ere related to lood. Hal o the bridgeailures e8a+ined #ere bound u0 #ith debris. ;lo# #ith an angle o attac3 to the

bridge also inluenced bridge stabilit because s3e#ed lo#s tend to increase the rate

o scour around the bridge, and also e8ert a torsional orce to bridges. ;lo# to#ard abridge +a start #ith no angle o attac3 but graduall s3e#s to the bridge i channel

+igration occurs. ;igure 1 sho#s ((6 bridge ailures #ere associated #ith s3e#ed

lo#s.

Ta)le /+ Scour De,t$ and Nu-)er of Bridge Failures

Scour de,t$ 0-1 Nu-)er .ercentage

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".2>!." 1

!.">2." !2

2.">9." !

9.">1"." '

1".">12." !

?ot deter+ined 1( 'Total ' 1""

De)ris Flood S%e2 flo2

0

5

10

15

20

25

30

35

Nu-)erof)ridgefailures

926

2"6((6

FI"+ *+ Occurrence of de)ris3 flood3 and s%e2 flo2 during )ridge failures

"eotec$nical condition

Geotechnical condition in%ol%es soil t0es and oundation t0es. Cohesionless soilsare generall erodible as o00osed to silt and cla. The ti+e re=uired to reach the

+a8i+u+ scour de0th is a00ro8i+atel hours in sand, das in clas, +onths in

glacial till and sandstone, ears in li+estone, and centuries in granite 5Richardson and

Da%is !""17. Table ' indicates +ost o bridge ailures occurred in the erodibleri%erbed +aterials, such as cobble:gra%el and sand, #hile silt and cla contributed to

1(6 o total ailures. ;ailure could also occur in +udstone:siltstone and earth loa+

but e#er cases #ere noted. The ar+ored laers o gra%els:cobbles are al#asdee+ed as non>erodible) ho#e%er the +a o%erlie erodible laer 5e.g. silt or sand7.

n this case, scour can 0rogress onto the underling silt or sand

Ta)le 4+ Soil Ty,es and Nu-)er of Bridge Failures

Soil ty,es Nu-)er .ercentage

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Boulders ! 2Cobbles : gra%els !!

$r+ored gra%els : cobbles ( 11

&and or ine &and #ith gra%el or cla 2 1(udstone:siltstone 1 '

&ilt:cla 2 1(thers 5earth loa+7 1 '

?ot deter+ined 1" !Total ' 1""

n ter+s o oundation t0es, shallo# oundations are +ore susce0tible to scour

than dee0 oundations. Table ( sho#s bridges su00orted b reinorced concrete 0ilesha%e the highest 0ercentage o ailures. &0read ootings contributed to the second

highest 0ercentage o bridge ailure under scour e%ents, ollo#ed b ti+ber 0iles.

&teel HP 0iles and un3no#n oundations clai+ed the lo#est ailures under scourconditions in the case studies e8a+ined.

Ta)le 5+ Foundation Ty,es and Nu-)er of Bridge Failures

Foundation ty,es Nu-)er .ercentage

&0read ooting !!

Concrete reinorced 0iles 12 (!

HP &teel Piles ! 2

Ti+ber 0iles 2 1(

-n3no#n oundation 1 '

?ot deter+ined 2 1(

Total ' 1""

Structural condition

Table 2 su++ari4es bridge t0es 0ertinent to scour>induced ailures. n the cases

e8a+ined, bridge t0es ha%e been docu+ented in !! o ' cases. ;ailures o the slab>on>girder bridges #ere +ost encountered during scour e%ents. Girder bridges #ith

si+0l su00orted s0ans #ere +ore susce0tible to scour than those #ith continuous

s0ans. n contrast to girder bridges, arch and truss bridges #ere less encountered in

the cases e8a+ined.&cour can initiate bridge ailure at dierent structural co+0onents such as bridge

dec3, abut+ents, 0iers, or bridge oundations. ;igure ! illustrates ailures o dierent

structural co+0onents #hen the bridges #ere subjected to scour. n +ost casese8a+ined, ailures o bridge oundations triggered ailures o bridge 0iers or

abut+ents. $s such, in ;igure !, oundation ailures #ere considered as a 0art o 0ier

and abut+ent ailure. ;igure ! sho#s that 0ier ailure #as accounted or 16 thetotal ailures, #hich is ollo#ed b abut+ent ailure. $but+ent ailure #as ound to

be inluenced b channel +igration and slo0e ailure at the abut+ent. thers ailures

#ith lo#er 0ercentage consisted o #ashout o bridge dec3 and bridges tendenc to

ail b scour.Page


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Ta)le 6+ Bridge Ty,es and Nu-)er of Bridge Failures

Bridge ty,es -aterials Nu-)er .ercentage

$rch concrete 1 '

>>> steel 1 '

Bea+:Girder concrete 9 1

>>> steel 11 '"

Bo8 girder concrete 1 '

Truss steel 1 '

?ot deter+ined > 1( '

Total ' 1""

A* A/ A4 A50

5

10

15

20

25

1(6

6

$1I Pier ,ailures

$!I $but+ent ,ailuers$'I Gthers

$(I ?ot $%ailable

Nu-)erof)ridgefailures

1B6

16

FI"+ /+ Failures of )ridge co-,onents due to scour

BRID" FAILUR 7ODS UNDR SCOUR CONDITIONS

Based on the assess+ent o the case histories, our ailure +odes #ere identiied,including %ertical ailure, lateral ailure, torsional ailure, and bridge dec3 ailure.

Table indicates that +ost bridge ailures #ere associated #ith lateral ailure,

ollo#ed b %ertical ailure. n co+0arison, torsional ailure and bridge dec3 ailure#ere less encountered. The ter+ othersin Table reers to a non>structural ailure o

a bridge, such as a slo0e ailure at an abut+ent or #ashout o an a00roach to an

abut+ent. ;i%e o the ' cases studied #ere classiied as others,as channel +igration0roduced intense scour to the a00roaches o the abut+ents.

The ollo#ing section #ill characteri4e each o the ailure +odes.

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#ertical failure

Bridge %ertical ailure under scour conditions could be attributed to a co+bination oactors such as inade=uate soil su00ort and 0ile instabilit. n general, bridge %ertical

ailure due to scour could be generali4ed into our categories as noted in ;igure '.

The consisted o inade=uate bearing ca0acit o shallo# oundation 5;igure '5a77,0enetration o riction 0iles 5;igure '5b77, under+ining o 0ile toe 5;igure '5c77, and

0ile buc3ling 5;igure '5d77.

&hallo# oundations tend to lose their %ertical bearing ca0acities #hen scourunder+ines the oundations and results in inade=uate soil su00orts as sho#n in ;igure

'ErrorI Reerence source not ound5a7. The &choharie Cree3 Bridge is an e8a+0le

that scour under+ined the bridge s0read ootings, causing the o%erall bridge ailure.

Ta)le 8+ Failure 7odes and Nu-)er of Bridge Failures

Failure -odes Nu-)er .ercentage

#ertical failure 11 '"6

>>>Buc3ling 5!7 5267

Lateral failure 1( '6

>>>&tructural hinging 527 51(67

>>>Pusho%er ailure 5(7 51167

Torsional failure 1 '6

Bridge dec% failure 1 '6

Ot$ers 2 1(6

Not identified ( 116

Total ' 1""6

Bridges on dee0 oundations can also ail under scour conditions as a result o

inade=uate %ertical bearing ca0acit. ;or riction 0iles, the %ertical bearing ca0acit

is reduced due to the reduction o s3in resistance #hen scour re+o%es soil around the0iles. ;igure 'ErrorI Reerence source not ound5b7 illustrates the 0enetration o

riction 0iles as a result o inade=uate %ertical bearing ca0acit. $s stated 0re%iousl,

the Hatchie Ri%er Bridge ailed because the riction 0iles s3in resistance decreased asa conse=uence o scour. ;or end bearing 0iles, the 0iles lose their %ertical bearing

ca0acit #hen scour under+ines the bearing laer 5e.g. hard laer or bedroc37 that the

0ile ti0s rest on, as seen in ;igure 'ErrorI Reerence source not ound5c7.

Piles +a also ail as a conse=uence o instabilit #hen scour increasingl re+o%esthe soils around the 0iles, resulting in an increase o the unsu00orted 0ile length, as

seen in ;igure 'ErrorI Reerence source not ound 5d7. The slender 0iles tend to

buc3le under the a8ial load ro+ the bridge su0erstructure or a co+bination o a8ial

and lateral loads. oreo%er, corrosion o the 0ile cross>section also contributes to the0ile buc3ling ailure. ;or e8a+0le, corrosion resulted in a00ro8i+atel ((6

reduction o cross>section o ti+ber 0iles in the Hatchie Ri%er Bridge, 5Tho+0son1"7, and 2"6 reduction o cross>section o steel HP 0iles in the >1" Bridge o%er

the Jourdan Ri%er in ississi00i 5$%ent and $la#ad !""27. n ter+s o steel HP

sha0es, buc3ling can occur globall 5le8ural buc3ling7 or locall 5local buc3ling7.

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$s indicated in Table , +ost %ertical ailures #ere associated #ith inade=uate soil

su00orts and to a less e8tent, #ere relati%e to instabilit issue.

Lateral failure

Lateral ailure consists o 0usho%er ailures o 0iers, structural hinging o 0iles,3ic3>out ailures o oundations, and e8cessi%e lateral +o%e+ent o 0iers or

oundations.

Pusho%er ailures occur #hen trans%erse lood and debris loads incre+entall add tobridge 0iers until bridge 0iers ail. Pusho%er analsis is a nonlinear static analsis b

graduall increasing lateral loads until the colla0se o the structure, as sho#n in

;igure (5a7. n addition to causing 0usho%er ailure, debris tends to 0ressure the

hdraulic lo# do#n#ard, resulting in an e%en dee0er scour hole. The greater scourde0th in turns urther lo#ers the 0usho%er ca0acit o the bridge structure.

Griginalground line

ground line

a,ter scour

Griginal

ground line

ground line

a,ter scour

5a7 5b7

Griginal

ground line

PP

bedroc3

Griginal

ground line

ground line

a,ter scour

bedroc3

ground line

a,ter scour

P P

5c7 5d7

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FI"+ 4+ #ertical failure of )ridge foundations 0a1 under-ining of footing )ase3

0)1 ,enetration of friction ,iles3 0c1 under-ining of ,ile ti,3 0d1 )uc%ling of ,iles

&tructural hinging occurs #hen trans%erse loads de%elo0 large bending +o+ents to

the structural ele+ents #hen their boundaries are ull or 0artial i8ed, as seen in

;igure (5b7. n the case studies e8a+ined, this ailure +ode #as obser%ed #ith the0ier ca0 rotating to#ards the u0strea+ direction 5el%ille and Cole+an !"""7. Piles#ith li+ited e+bed+ent into a 0ile ca0 +a ail in a hinging +ode due to inade=uate

bending +o+ent resistance. n addition, loods carring large and hea% debris such

as stones +a attac3 the 0iers or 0iles, resulting in a 0otential structural hinging5el%ille and Cole+an !"""7.

/ic3>out ailure o oundations occurs #hen scour results in #ash out o the 0iles

ro+ the location o 0ile ti0s, as de0icted in ;igure (5c7. Bridge that ails due to 3ic3>out has relati%el high lateral su00orts ro+ su0erstructures but ails to sustain

ade=uate lateral ca0acit at the oundations. &hallo# oundations are e8ce0tionall

susce0tible to 3ic3>out ailures. Piles +a also ail in 3ic3ing out once scour

de%elo0s at a suicient de0th to +obili4e 0ile ti0 laterall.

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FI"+ 5+ Lateral failure -odes of t$e )ridge 0a1 ,us$o&er failure3 0)1 structural

$inging3 0c1 %ic% out of foundations

Table sho#s structural hinging ailures accounted or 1(6 and 0usho%er ailuresor 116 o the total ailures.

Torsional failure

Torsional ailurereers to a torsional 5t#isting7 ailure o the structure or structural

co+0onents attac3ed b s3e#ed lo#s. ;lo#s #ith an angle o attac3 gi%e arise toeccentric lateral loads and de%elo0 tor=ues to bridge 0iers or abut+ents. n Table ,onl one case had the bridge 0iles t#isted 5el%ille and Cole+an !"""7, #hich #as

0ertinent to torsional ailure. $lthough torsional ailure +a not be a do+inant

ailure +ode, the torsion eect could co>e8ist #ith other t0es o bridge ailuresunder s3e# lo# conditions.

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Bridge dec% failure

Bridge dec3 ailures +a occur #hen bridge dec3 is outlan3ed b loods. Debrisloads contribute to the #ashout o bridge dec3 in lood e%ents. Bridge dec3s on

si+0le>su00ort s0ans are susce0tible to the lood i the dec3 is not structurall

attached to the su0erstructure ele+ents. ne a+ong ' e8a+ined cases #as related tobridge dec3 ailure as indicated in Table .

R7DIAL 'OR!

Re+ediation o the bridge da+age due to scour included retroitting the da+aged

su0erstructure and oundation ele+ents o bridges, and i+0le+enting scour

counter+easures. Te+0orar Baile bridges #ere built or those bridges #hose s0ans#ere #ashed out or colla0sed. $lternati%el, so+e da+aged bridges #ere orced to

close and ne# bridges #ere constructed. ;oundation rehabilitation included

under0inning the da+aged 0ile oundations #ith steel HP or 0i0e 0iles e+bedded to

the co+0etent soil laer. Deteriorated 0iles #ere re0laced #ith sound 0iles, and inso+e cases, battered 0iles #ere constructed or the oundations to resist lateral loads.

Grouting techni=ues #ere also used as re+edial +easures to ill the scour holes unders0read ootings.

t is also i+0ortant to include scour 0rotection and channel stabili4ation as a 0art o

re+edial #or3. &cour 0rotection includes 0lacing roc3 ri0ra0 and ilter cloth on theri%erbed under bridges. Channel stabili4ation includes stabili4ing di3es to 0re%ent the

de%elo0+ent o +eander or realigning channels to establish s+ooth lo#s.

CONCLUSIONS

This 0a0er re%ie#ed case histories o bridge ailures under scour conditions.

Totall ' cases #ere gathered and anal4ed in ter+s o structural, hdraulic, andgeotechnical conditions 0ertaining to scour>induced bridge ailures. This 0a0er also

su++ari4ed bridge ailure +odes relati%e to scour and discussed scour re+ediation

+easures. Based on the analses, the ollo#ing conclusions can be dra#nI17 Local scour is the do+inant scour t0e 5i.e. (67 res0onsible or bridge

ailure, ollo#ed b channel +igration 51(67 and contraction scour 5267. ost o

scour de0ths 5i.e. u0 to (167 ranged ro+ ".2 to 2." + but the +a8i+u+ scour

de0th could be u0 to 12 +.!7 Bridges in cohesionless soils #ere +ore susce0tible to scour than cohesi%e

soils. n the cases e8a+ined, +ost bridge oundations encountered #ere concrete

0iles 5(!67 and s0read ootings 5!!67.'7 Bea+:girder bridges #ere +ost encountered in the cases e8a+ined. ore

ailure or da+age occurred at bridge 0iers than bridge abut+ents.

(7 Bridge ailure +odes included %ertical ailure, lateral ailure, torsional ailure,and bridge dec3 ailure. $+ong these ailure +odes, lateral ailure 5'67 #as

+ost 0re%alent, ollo#ed b %ertical ailure 5'"67.

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RFRNCS

$+erican $ssociation o &tate High#a and Trans0ortation icials 5$$&HT75!""97. AASHTO LRFD Bridge Design Specifications. (th Ed., $$&HT,

!".

Lagasse, P. ;., Clo00er, P. E., @e%enbergen, L. 21 bridge ailure.

Transportation Research Board, !(>'2.

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Iscepgi p 21 Lin