Structures Strengthened with Bonded Composites (Woodhead Publishing Series in Civil and Structural Engineering)

554 Pages·2020·18.827 MB·English

by  Zhishen Wu, Yufei Wu, Mohamed F.M. Fahmy

Structures Strengthened With
Bonded Composites
Woodhead Publishing Series in Civil and
Structural Engineering
Structures Strengthened
With Bonded Composites
Zhishen Wu
Yufei Wu
Mohamed F. M. Fahmy
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Contents
Preface ix
Symbols xi
1 Fundamentalbehavioroffiber-reinforced polymersandtheirbonding
technique 1
1.1 Fiber-reinforcedpolymerconstituents 1
1.2 Characteristicsoffiber-reinforcedpolymercomposites 12
1.3 Fiber-reinforcedpolymerbondingtechniquefortheconcreteand
steelstructures 78
References 83
2 BondcharacteristicsanddebondingmechanismofFRP(cid:1)concrete
interface 87
2.1 Interfacial fracturesanddebondingmodes 87
2.2 StresstransferandfracturepropagationofFRP(cid:1)concretejoints 89
2.3 Short-termbehaviorofFRP(cid:1)concreteinterface 109
2.4 Long-termbehaviorofFRP(cid:1)concreteinterface 134
2.5 DurabilityofFRP(cid:1)concreteinterface 152
2.6 EnhancedFRPbondingsystem 169
References 181
3 Fiber-reinforcedpolymer-strengthenedtensilemembers 187
3.1 ExperimentalinvestigationsofFRP-strengthenedtensilemembers 187
3.2 FractureenergyapproachforanalyzingtensilepropertiesofFRP-
strengthenedtensilemembers 195
3.3 Modelingoftensionstiffeningeffect 205
3.4 Formulationofcrackspacing 218
References 225
Furtherreading 226
4 Flexuralstrengtheningofstructures 227
4.1 Introduction 227
4.2 Flexuralstrengtheningmethodsforstructuralmembers 228
4.3 Effectofflexuralstrengtheningontheperformanceofstructural
members 229
4.4 BondinganddebondingmechanismsinFRP-strengthenedRC
members 245
vi Contents
4.5 Designofflexuralstrengthening 264
4.6 PerformanceenhancementsforFRPflexuralstrengthening 281
4.7 Specialfieldapplications 296
References 311
Furtherreading 314
5 Shearandtorsionalstrengtheningofstructures 315
5.1 Introduction 315
5.2 Whyshearandtorsionstrengthening? 315
5.3 WhatisshearandtorsionstrengtheningwithFRP? 316
5.4 Failuremodesofshearstrengthenedbeams 318
5.5 FundamentalmechanismforFRPretrofitting 320
5.6 Experimentalinvestigationofparametersinfluencingshear
capacities 323
5.7 Numericalinvestigationofparametersinfluencingshearcapacities 324
5.8 Shearstrengthmodels 344
5.9 Numerical-basedmodelforpredictionofshearcapacity 362
5.10 Failuremodesoftorsionalstrengthenedbeams 365
5.11 ResistancemechanismofFRPtorsionalstrengthening 369
5.12 EvaluationoftorsionalstrengthofFRP-strengthenedelements 371
References 378
Furtherreading 384
6 FRPstrengtheningofconcretecolumns 387
6.1 Performanceofunder-designedexistingstructures 387
6.2 Provisionsofcurrentseismicdesigncodes 392
6.3 StrengtheningofRCcolumns 392
6.4 FRPasexternalreinforcement forexistingRCcolumns 394
6.5 Modelingofstress(cid:1)strainbehaviorofFRP-confinedconcrete 406
6.6 Ductilityenhancement 421
6.7 DurabilityofFRP-confinedconcretecolumns 426
6.8 DesignmethodsofFRPjacketfordeficient RCcolumns 436
6.9 Numericalsimulationofcolumnsunderaxialandlateralloads 446
6.10 Evaluationofdesign-orientedmodelsinsimulatingRCcolumns
retrofittedwithFRPjacketsunderaxialandlateralloadings 448
6.11 RecoverabilityofFRP-retrofittedcolumns 450
References 468
7 Reinforcingspallingresistanceofconcretestructureswithbonded
fiber(cid:1)reinforcedpolymercomposites 481
7.1 Introduction 481
7.2 Spallingresistanceofbeamswithfiber-reinforcedpolymersheets 483
7.3 Spallingresistanceofstructureswithbidirectionalfiber(cid:1)reinforced
polymersheets 494
7.4 Experimentalstudyonarchedbeams 512
Contents vii
7.5 Spallingpreventiondesignmethod 515
7.6 Selectionofmethodtopreventspalling 522
7.7 Conclusions 523
References 523
Furtherreading 524
Index 525
Preface
Strengthening or stiffening of civil infrastructure using externally bonded fiber-
reinforced polymer (FRP) composites such as FRP plates, sheets, and grids has
become a promising structural strengthening technique. It has also gained much
popularity recently, particularly in rehabilitation of structures/infrastructures due to
the worldwide deterioration problems and earthquake hazards. Their high strength-
to-weight ratio, durability in adverse environments, and high fatigue performance
make them a good choice for civil engineering applications. Moreover, FRP sheets
can easily be externally bonded to the surface of structural members. However, the
brittle behavior of FRP materials, low FRP reinforcing ratio, debonding behavior,
and other undesirable failure modes often limit the expected gains in structural per-
formance and leave a large portion of potentials of FRP materials unused. Besides,
the practice of the FRP bonding technique was being widely adopted without a
thorough examination of the many parameters involved. Facing these problems,
considerable studies have been conducted recently and good achievements have
beenachievedthroughtheseactiveefforts.
Thisbookaims topresentacomprehensive accountofstrengtheningofconcrete,
reinforced and prestressed concrete, masonry, steel, and other composite structures
using externally bonded FRP composites with emphasis on giving a systematic and
fundamental investigation on bonding and debonding behavior of FRP(cid:1)concrete
interface and structural performances of FRP-strengthened structures with a combi-
nation of experimental, theoretical, and numerical studies, developing the analytical
models and design codes, and some emerging and innovative strengthening techni-
ques. FRP strengthening of different kinds of structures including bridge, tunnel,
building and historic structures, and underwater constructions is discussed in the
book.Themaintopicscoveredincludethefollowing:
(cid:1) FundamentalbehaviorofFRPandbondingtechnique
(cid:1) BondcharacteristicsanddebondingmechanismofFRP-to-concreteinterface
(cid:1) FRP-strengthenedtensilemembers
(cid:1) Flexuralstrengtheningofstructures
(cid:1) Shearandtorsionalstrengtheningofstructures
(cid:1) FRPstrengtheningofconcretecolumns
(cid:1) ReinforcingspallingresistanceofconcretestructureswithbondedFRPcomposites
Clear classification and discussions are made on various interfacial failure
modes from both microscopic and macroscopic viewpoints with a combination of
x Preface
experimental, theoretical, and numerical studies. After clarifying the interfacial
failure mechanisms, a comprehensive design guideline including the optimum
design of strengthening composites and FRP-strengthened structures is described.
Efforts are also made to develop effective FRP strengthening with prestressed and
newcompositematerials(newlydevelopedPBOandDyneemafibersheets).
Symbols
A aramid
εeff theeffectivetensilestrain.
f
Vf thejacketcontribution
w
P theultimateload
u
μ responseductilityfactorofpier.
R
a beamshearspan
A thegrosscrosssectionoftheelement.
g
ag peakgroundacceleration.
A cross-sectionalareaofreinforcingbars
s
A areaoflongitudinalsteelreinforcement
sl
A areaofstirrupsbarsreinforcement
st
A totalcross-sectionalareaofshearreinforcementinspace
w
B memberwidth(unit:mm)
b beamwidth
b(cid:1) t-section
b widthofconcreteprism
c
b widthofFRPcomposites
f
BF debondingfailure
BFRP basaltfiberreinforcedpolymer
b webwidth
w
C carbon
CA interfacebetweenconcreteandadhesive
cc concretecovertothemaincolumnreinforcement.
C concretecrushing
C
CFRP carbonfiberreinforcedpolymer
COV coefficientsofvariation
C factordependingonthebilinearfactorr.
R
cu neutralaxisdepth
D thecolumndimensionintheloadingdirection
d effectivedepthofelement
d bardiameterofthemaincolumnreinforcement
b
D anequivalentcolumndiameter
e
d theeffectivedepthofFRPsheet
f
DFRP dyneemafiberreinforcedpolymer
D thedead(permanent)load
n
d debondinglengthofreinforcingbar
s
d diameterofstirrupssteel
st
E themodulusofelasticityoftheconcrete
c
E theelasticmodulusofFRP.
f
E theelasticjacketmodulus
j