Fatigue Effects on Bridges

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PRESENTATION ON

FATIGUE EFFECTS ON BRIDGES

BY

JANARDHAN C N


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I-35W Mississippi River bridge

Loaction : USA

Constructed : 19!


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I-35W Mississippi River bridge

Co""apsed in t#e $ear %&&! serving 'or (& $ears


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)utai )artanegara *ridge

Loaction : Indonesia

Constructed : %&&1


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)utai )artanegara *ridge

Co""apsed in t#e $ear %&11 serving 'or 1& $ears


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Loaction : Sout# )orea

Constructed : 19!9

Seongsu *ridge


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Seongsu *ridge

Co""apsed in t#e $ear 199( serving 'or 15 $ears


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Loaction : USA

Constructed : 195+

Co""apsed : 19+3

Mianus River *ridge

Served 'or %5 $ears


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Loaction : United States

Constructed : 19&&

)in,ua

*ridge


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Co""apsed in t#e $ear %&&3 Served 'or 1&3 $ears

)in,ua

*ridge


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.ie"ding /e'"ection be$ond a certain stage *uc0"ing atigue 2nvironenta" degradation 4ibrationa" Modes Ipact Wear

Some common causes for failure of Bridges


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atigue is de'ined as t#e "oss o' resistance o' a ateria" it#

t#e app"ication o' d$naic or repeated "oads6

7#e 'atigue 'ai"ure is c#aracteri,ed b$ t#e "oss o' strengt#due to t#e crac0s grot#6

A "oad o' insu''icient agnitude to cause 'ai"ure in a sing"eapp"ication a$ "ead to 'ai"ure i' it is reoved and reapp"iedrepeated"$6

atigue is genera""$ caused b$ repeated c$c"es o' tensi"e"oading6

atigue crac0s in an$ cases are ver$ 'ine reaining tig#t"$c"osed at iniu "oad and #ence di''icu"t to 'ind b$ visua"e8aination a"one6

Fatigue


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Characteristics of fatigue

fracture

atigue 'racture ta0e p"ace in t#ree stages during t#e "i'e o' a

structure :16 Initiation o' Microscopic /e'ect

%6 ropagation o' Crac0s in radua" Manner

36 ina" Rupture

Crac0ing originates ost"$ on t#e sur'ace at a point o' stressconcentration6

In ost e"ded stee" structures t#e crac0 initiation p#asedoes not e8ist as crac0;"i0e e"d de'ects are invariab"$present in t#e6 7#us t#e 'atigue "i'e o' a connectioncontaining e"ds is entire"$ due to crac0 grot#6

ina" 'ai"ure usua""$ occurs in a tension region #en t#ereduced section is no ore su''icient to carr$ t#e pea0 "oad.


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A sa"" crac0 initiated gros s"o"$ it# t#e repetition o'stress c$c"es6 As t#e crac0 propagates t#e cross-section

reduces and t#e stress on t#e reduced cross section increases.ina""$ rupture occurs #en t#e reaining area is no "ongersu''icient to support t#e app"ied "oad6


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Mechanism of Crack Initiation

7#e noina" or t#e stress it#out concentration e''ects a$ bebe"o proportiona" "iit6 At t#is stage s"ip ig#t occur in an

cr$sta""ograp#ic p"ane due to e8cessive s#ear stress on t#ep"ane6 7#is ig#t be a 'ine s"ip o' order 1&- be"o ad


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Modes of failure

/epending on t#e t$pe o'opening or disp"aceents o'crac0 'ront t#e t#ree priar$icroscopic 'racture odesare:

Mode I (Tension, Opening)

Mode II (In-Plane Shear, sliding) Mode III (Out-of-Plane Shear, Tearing)


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Types of fatigue Loer t#e stress ranges i6e6 t#e di''erence beteen t#e

a"ternating a8iu and iniu stresses t#e "arger t#enuber o' c$c"es t#e structure can it#stand be'ore t#eoccurrence o' 'racture6

7#e to ain t$pe o' atigue process are:

16 =ig#-C$c"e Lo-Stress atigue

%6 Lo-C$c"e =ig#-Stress atigue


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Types of fatigue (contd…) =ig# C$c"e ; Lo Stress atigue

2"asticit$> =ig# C$c"e 'atigue corresponds to re"ative"$sa"" stress ap"itudes #ic# induce "arge nubers o'c$c"es to 'ai"ure ?greater t#an 1&5@6

Lo C$c"e ; =ig# Stress atigue

2"asto-"asticit$> Lo c$c"e 'atigue corresponds tostresses above t#e $ie"d stress #ic# induce "oernuber o' c$c"es to 'ai"ure ?sa""er t#an 1&5@6


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Types of fatigue loading

Constant Ap"itude atigue Loading

4ariab"e Ap"itude atigue Loading


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Types of fatigue loading

(contd…) Constant ap"itude

"oading re'ers to c$c"ic"oading #ose ap"itudeis constant it# tie

7#is t$pe o' "oadingusua""$ occurs inac#iner$ parts suc# ass#a'ts and rods duringperiods o' stead$-state

rotation6

Constant Ap"itude atigue Loading


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Types of fatigue loading (contd…)


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Types of fatigue loading(contd…)4ariab"e Ap"itude atigue Loading

4ariab"e ap"itude "oading re'ers to c$c"ic "oading#ose ap"itude is variab"e it# tie

7#is t$pe o' "oading usua""$ occurs due to ve#ic"e"oading on bridges ind "oading on aircra't and ave

"oading on s#ips6


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Mec#anica" atigue Creep atigue

7#ero Mec#anica" atigue

Corrosion atigue Contact atigue

retting atigue

Forms of fatigue failures


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Fatigue Life

atigue "i'e is t#e nuber o' repeated c$c"es o' "oading ?A t @

t#at a ateria" i"" undergo be'ore it 'ai"s6

uber o' c$c"es reBuired to initiate a 'atigue crac0 is t#eFatigue Crack Initiation Life A i 6

uber o' c$c"es reBuired to propagate a 'atigue crac0 to acritica" si,e is ca""ed t#e Fatigue Crack Propagation Life p6

A t C A i D A p


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atigue 'ai"ure 2va"uation is in'"uenced b$ a nuber o'

uncertainties an accurate prediction o' 'atigue "i'e is di''icu"teven 'or a ver$ sip"e detai"6

atigue 'ai"ure prediction is di''icu"t in structura" coponents duet#e 'o""oing uncertain 'eatures6

7#e e''ect o' environent in #ic# t#e structure is 'unctioning6

/i''icu"ties in accurate ca"cu"ation o' interna" stresses due toe8terna" 'orces in critica" "ocations in t#e structure6

Fatigue Life !aluation


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"amples for Fatigue facture

Fatigue cracking in a bridge girder starting from weld defects at a weld

intersection point


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Radial and Tangential Crack.


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Fatigue cracking in the hangers of the Mashita Bridge in Japan


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Fatigue Cracking in Stringers at Timber Tie Connections


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Fatigue cracking in the Riveted Connection of CrossBracing !lements


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Fatigue Cracking in Bridge "irders with Cope#oles at Severe Stress

Concentration $ocations


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Fatigue Cracking of Cover%late !nds


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Fatigue #ssessment of $igh%ay Bridges*S 5(&&-1& speci'ies t#e t#ree procedures 'or t#e assessent

o' detai"s in t#e =ig#a$ bridges

Assessent it#out daage ca"cu"ations

/aage ca"cu"ation sing"e #ee" et#od

/aage Ca"cu"ation 4e#ic"e Spectru Met#od

7#e se"ection o' t#e appropriate procedure depends on t#e

detai" c"assi'ication design "i'e "oad spectru and assuedannua" '"o o' coercia" ve#ic"e6


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Classi&cation of 'etails 2ac# part o' a constructiona" detai"s sub


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'etail Type * +on ,elded


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'etail Type- * ,elded details otherthan the nd Connection Mem.er


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'etail Type- * ,elded details at ndConnection of Mem.er

S d d i hi l


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Standard Fatigue /ehicle

A8"e Arrangeent

"an o' Standard A8"e

' i i f l f F i


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7#ree "ane dua" carriagea$s

'esignation of lanes for Fatigue 0urposes

7o Lane S"ip Road 7#ree "ane sing"e carriagea$

7o "ane sing"e carriagea$


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Assessent it#out /aage Ca"cu"ations


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/aage Ca"cu"ation Sing"e 4e#ic"e Met#od

7#is et#od deterines t#e 'atigue "i'e o' t#e detai"s and a$ beused #ere a ore precise assessent is reBuired6

rocedure:

App"$ t#e standard 'atigue ve#ic"e to eac# s"o "ane and eac#ad


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" " " # " # d


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/aage Ca"cu"ation Sing"e 4e#ic"e Met#od /erive t#e stress spectru E v1 E v% etc6 'or eac# stress

#istor$6

/eterine t#e e''ective annua" '"o o' coercia" ve#ic"esnc i""ion appropriate to eac# stress spectru as 'o""os:

Annua" '"o o' coercia" ve#ic"e ? nc 8 1& @

/ C " " " 4 # " M # d


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/aage Ca"cu"ation Sing"e 4e#ic"e Met#od or eac# stress range E v o' eac# stress spectru deterine

t#e appropriate "i'etie daage 'actor d1%& 'ro t#e daage

c#art6


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/aage Ca"cu"ation Sing"e 4e#ic"e Met#od Li'e tie daage 'actor to be u"tip"ied b$ appropriate nc va"ue

/eterine t#e va"ue o' t#e ad


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/aage Ca"cu"ation 4e#ic"e Spectru Met#od7#is et#od invo"ves an e8p"icit ca"cu"ation o' MinerFs suation

and a$ be used 'or an$ detai" 'or #ic# t#e E r ; re"ations#ip

and stress spectru is 0non6

/esign spectru:

7#e individua" stress spectra 'or t#e detai" being assesseds#ou"d be derived b$ traversing eac# ve#ic"e in t#e "oad

spectru a"ong t#e various "anes6 Account s#ou"d a"so be ta0eno' t#e possibi"it$ o' #ig#er stress ranges due to soe o' t#eve#ic"e occurring siu"taneous"$ in one or ore "ane and ina"ternating seBuence in to "anes6

Ca"cu"ation o' daage:Using t#e design spectru t#e va"ue o' MinerFs suation s#ou"dbe ca"cu"ated6 7#is va"ue s#ou"d not be "ess t#an 1 'or t#e'atigue "i'e o' t#e detai" to be e8cepted6

" id #i" d i i "d d


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enera" guidance #i"e designing a e"dedstructure it# respect to 'atigue strengt#

Adopt butt or sing"e and doub"e beve" butt e"ds in pre'erenceto 'i""et e"ds6 Ai to p"ace e"d particu"ar"$ toe root and e"d end in area o'

"o stress6 Avoid detai"s t#at produce severe stress concentration or poor

stress distribution. rovide gradua" transitions in sections and avoid reentrant notc#

"i0e corners6 Use continuous rat#er t#an interittent e"ds6 Avoid a0ing attac#ents on parts sub


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Thank you

Fatigue Effects on Bridges

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