Principles of reinforced concrete

587 Pages·2014·43.744 MB·English

by  Zhenhai Guo

Principles of
Reinforced Concrete
Zhenhai Guo
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Preface
The courses “Theory of Reinforced Concrete Structures” [1-1] and “Strength and
Constitutive Relation of Concrete” [1-2] were started in early 1980’s for the post-
graduatestudentsinstructuralengineeringandrelatedfieldsinTsinghuaUniversity.
The lectures, and the syllabus and contents of both courses are varied during the
teachingpractice.Twocoursesarecomposedandnamed“PrinciplesofReinforced
Concrete”in1990’s.Theauthorgavealectureonthiscourseforseveralyearsand
wrote the textbook ofsame name [1-3], based on the teaching draft.
Afterthebookwaspublishedin1999,itisalsoadoptedasthetextbookormain
referenceforsimilarcoursesofbothpost-andunder-graduatesofmanyuniversities
in China. And, it is helpful as well for the university lecturers. In addition, some-
timesthebookisusedbythestructuralengineersduringtheirscientificortechnical
work.
In 2001, Education Committee of Beijing decided to establish “the elite text-
books for university education of Beijing’, and the textbook was selected after
appraisement. The new textbook is renamed as “Principle and Analysis of Rein-
forced Concrete” [1-4] and published in 2003. The new textbook or the second
edition contains most contents of the original one, but some chapters and sections
are reformed and two new chapters, i.e. general analysis method of structural
memberanddurability,areadded.Inaddition,theexercisesareattachedtoitstext.
This book is the English version of textbook “Principle and Analysis of
Reinforced Concrete” (in Chinese), but some contents are modified and slightly
abridged to reduce its length. There are four parts including twenty chapters in
this book.
InPartOne,thestrengthanddeformationbehavioranditsvariationregularityof
concreteareintroducedindetail,basedonitsbasiccharacteristicandfailuremech-
anism. The main mechanical behaviors of various structural concrete, i.e. high-
strength,light-weight,andfiberconcrete,arepresentedaswell.And,themulti-axial
strengthand constitutiverelation of concreteare brieflycontained.
The combination function of reinforcement and concrete is a special problem
with importance, when reinforced concrete is considered as a composed structural
materialandisdistinguishedfromasinglestructuralmaterial.So,bondanddefor-
mation deference between reinforcement and concrete, and confined concrete are
discussed inPart Two.
In Part Three, the strength,crack, and deformation of flexuraland compressive
members, and shear- and torsion-resistances of structural members of reinforced
concrete are introduced in detail based on the corresponding experiments. And,
the general regularities, working mechanisms, and analysis methods of them are
concluded.
A reinforced concrete structure may experience some extreme circumstances
during its long life, e.g. earthquake, explosion, fatigue, high temperature (fire), or
long-term damage (durability). So, the special behaviors of reinforcement and
XV
XVI Preface
concretematerials,andthemechanicalresponsesandanalysismethodsofthestruc-
tural membersunder these conditions are introduced brieflyin Part Four.
“ReinforcedConcreteStructures”orthesimilar[1-5]isacoursefortheunder-
graduate students of Structural Engineering in Chinese university. The main
objective of it is to help them to conduct the structural design. Therefore, the
main contents of the course include: the mechanical behaviors of reinforcement
and concrete are briefly introduced, the behavior, calculation method, and require-
ment of design and construction of the basic structural members under various
internal forces are presented in detail, and the concept and method of structural
design and relevant designcodes are introduced and explained.
This book is used for the post-graduate students in structural engineering. The
maincontentsareresearchandanalysisofthemechanicalbehavioranditsregularity
ofreinforcedconcretestructuralmembers,andthemainobjectiveistosolvevarious
questions occurred in engineering practice. Therefore, the general regularities of
strengthanddeformationofconcreteunderuni-andmulti-axialstresses,evenunder
severalextremecircumstances,areintroducedsystematically,asthisisthebasisfor
understandingandanalyzingthestructuralmembers.Whenthemechanicalbehavior
ofthestructuralmembersundervariousconditionsarediscussed,theresultsofcor-
respondingexperimentalinvestigationsareemphasized,thestressanddeformation
states,crackingandfailureprocess,andinfluencesofimportantfactorsareanalyzed
indetail,andtheworkingmechanism,theprincipleandmethodofcalculation,and
thedeterminationsofthetechnicalindicesareconcluded.Itishopedthatthereader
notonlyknowsthegeneralregularitiesofthematerialsandmembersofreinforced
concrete,butalsounderstandsthegeneralwayandreasonablemethodforanalyzing
and solving the practical problems in reinforced concrete structural engineering,
after readingthis book.
Whenthisbookissenttopress,theauthorsincerelythankstheprofessorsofelder
generation,whoworkedintheDepartmentofCivilEngineering,TsinghuaUniver-
sity. They worked and studied seriously and their teaching experiences [1-5][1-6]
and research achievements in reinforced concrete structure field enrich my knowl-
edge,whichpartlycomposesthebasisofthisbook.Mycolleagues,includingtech-
nicians and workers, and post- and under-graduate students, who worked together
withintheprocessesofexperimentalandtheoreticalresearcheswithinmanyyears,
are appreciated as well. Their cooperation with effort helps to bring about the
research achievement, which substantiate and improve the contents of this book.
In addition my special thanks is due to my wife, retired professor Suying Qian,
who not only patiently typed and input the entire manuscript of this book to form
the original computer text, but also takes care thoughtfully of my life. Of course,
theprintandpublicationofthisbookisreliedontheeffortsofTsinghuaUniversity
Press,itisalsoappreciated.
Zhenhai Guo
September2013
CHAPTER
1
Introduction
CHAPTER OUTLINE
1.1 Developmentandfeaturesofreinforcedconcretestructure.....................................1
1.2 Characteristicsofthiscourse...............................................................................4
1.1 Development and features of reinforced concrete
structure
Since the first product of reinforced concretewas manufactured and used in struc-
tural engineering, only about one hundred years have passed. Compared with soil
and timber structure, which is the earliest on earth, used by the original mankind,
themasonrystructureofstoneorbrickappearedintheearlysocietyofancientciv-
ilizations,andsteelandothermetalstructuresdevelopedafterthe IndustrialRevo-
lution,reinforcedconcretestructureistheyoungestoneamongthestructurefamily.
However,theperformanceandmanufacturetechniqueofreinforcedconcretestruc-
ture are continuously improving and being enhanced, structural configuration and
construction get morevariety, and the application scope is widely expanded. Now,
reinforced concrete structure is the most prosperous one in structural engineering
inmanycountries, especially inChina.
Now, the engineering fields using widely reinforced concrete structure are as
follows.
Buildingengineeringe variouscivil andpublicbuildings, single- andmulti-
storeyindustrialbuildings, high-rise andlong-span buildings.
Bridge and communication engineering e slab, beam, arch, and truss upper
structures,abutments,piers,andfoundations,slopeprotection,retainingwalls,
highway pavements, railway sleepers .
Hydraulic and harborengineering e dams, hydropower stations, coasts and
docks, offshore platforms,ponds and pipelines, aqueducts .
Undergroundengineering e tunnels, railways, mines, caissons,piles, foun-
dations ofheavyequipment,military defenseworks.
Specialengineering e television towers,transmission poles,viaducts, silos,
chimneys, pavements andparking apronsof airports ..Evenreinforced con-
crete structuresenterinto the machinebuildingfield, e.g. reactor vesselsand
1
PrinciplesofReinforcedConcrete.http://dx.doi.org/10.1016/B978-0-12-800859-1.00001-3
Copyright©2014TsinghuaUniveristyPress.PublishedbyElsevierInc.Allrightsreserved.
2 CHAPTER 1 Introduction
containment of nuclear power plants, hydraulicpresses, shipbuilding,lathes,
etc., which are occupied traditionallyonly by steel structures.
Theinherentcertaintyofacombinationofreinforcementandconcreteisdueto
themutualcompensationofthebehaviorofbothmaterialsandtheadvantageofeach
materialisfullyutilized.Concreteisthemainbodyofthestructuralmaterialandhas
someadvantages,e.g.easymanufacturing,utilizinglocalmaterials,lowinvestment.
However,concretehaslowertensilestrengthandisfragileandcrackseasily.There-
fore,onlywhenthereinforcementofapropertypeandquantityisputintothecon-
crete,thestrengthandductilityofthereinforcedconcretestructureisimprovedand
enhancedtosatisfythenecessarysafetyandserviceconditions.Inthemeantime,the
disadvantagesofreinforcement,e.g.poorenvironmentalstability,andcorrosionand
fireresistance,willbeovercomewhenitisburiedintoconcrete.So,reinforcement
andconcretecaneffectivelybecomposedofastructuralmaterialwithhighstrength,
good integrity,corrosion andfire resistances,and flexibleuses.
Inaddition,concreteisashapelesssubstanceandcanbemadeintoanystructure
ofcomplicatedshapeanddifferentsizes,whenapropermoldismanufacturedand
installed.Therearesomanydifferentreinforcedconcretestructureswhichinclude
notonlytheone-dimensionalmembers,e.g.beam,slab,column,ofsolidandhollow
sections of different shapes, but also the two-dimensional members, e.g. flat plate,
slab, wall panel, shear-wall,folded plates, and the three-dimensional,e.g. thin and
thick shells andirregularsolid, structures.
Reinforcedconcreteitselfiscomposedoftwomaterialsandcanalsobeusedasa
kindofstructuralmaterialandcombinedwithotherstructuralmaterialstocompose
various composite structures, such as reinforced concrete-steel and reinforced
concrete-masonry structures. Then, more varieties of structure scheme are devel-
opedand the adaptability and applicationscope ofit are expanded.
As reinforced concrete structure is widely used in engineering practice, the
requirementofproductionacceleratestheresearchworkinallaspects.Theplentiful
researchresultsonstructuralschemeandconfiguration,kindandqualityofmaterial,
constructiontechnique,mechanicalbehaviorofstructuralmembers,designconcept
andcalculationmethod,constructionmeasures,etc.,areachievedandgreatprogress
is made asbelow.
Some disadvantages of concrete material, such as higher dead weight, lower
crackingresistance,strengthincreasingslowly,andseasonallimitationofconstruc-
tion,havebeenimprovedorovercome,whenthetechnicalmeasures,whichinclude
selectionofrawmaterials,mixandcuretechnique,constructionmanagement,rein-
forcement construction, prestressing, and improvement of calculation method, are
utilized.
In order to enhance the performance of concrete and to reduce its self weight,
high-strength (>C50), light-weight (g ¼ 500e1900 kg/m3), fiber, and high-
performanceconcretesofvariouscategoriesaredevelopedsuccessivelyandapplied
inengineering practice.
Whenvariouschemicaladditivesaremixedintoconcreteduringitsmixing,the
higher workability, freezing resistance, high strength, and earlier coagulating of
1.1 Development and features of reinforced concrete structure 3
concrete are achieved, even heat-resisting and acid-resisting concrete can be ob-
tained. And, pumping, spraying, and self-compacting concrete may be used to
improve the manufacturing technique. All kinds of these concretes are suited to
different construction andapplication conditionsof reinforced concrete structures.
Thestrengthofthesteelreinforcementusedforreinforcedconcretestructureis
gradually increased from low value into medium and high values. The steel rein-
forcements of low relaxation and with anticorrosion coating are used frequently.
Variousresinsandcarbonicfiberbars(orsheets)ofhighstrengthandanticorrosion
are alsoused successfullynowtoreplace the steel reinforcement.
The behaviorof concrete under uni- and multi-axial stress states and itsfailure
criterion and constitutive relation have been investigated experimentally and theo-
retically, and great progress has been made. The strength and deformation of con-
crete under various conditions, e.g. repeated load, high-speed loading, sustained
load,at elevatedtemperature, are also tested and manyresultsare reported.
The bond behavior between reinforcement and concrete, including working
mechanism,characteristicvaluesofbondstrengthandslip,shapeandcalculation
modelofs-scure,havebeeninvestigatedformanyyears.Theanchorageofrein-
forcement is important in engineering practice and an effective measure is avail-
able now.
The mechanical behaviors of various structural members under static and dy-
namic loads are always the key topics of research on reinforced concrete. Most of
themalreadyhavedefiniteconclusionsandripecalculationmethods.Themechan-
icalresponsesofthemunderextremecircumstances,e.g.earthquake,explosion,fire
accident,alsohaveplentyexperimental and theoretical results.
Intheinitialstageofapplication,thedesignconceptandcalculationmethodofa
reinforcedconcretestructurearebasedontheallowablestressandelasticanalysis,
whichfollowthatofthesteelstructure.Then,theywerechangedintosinglesafety
coefficient and ultimate strength analysis respectively. Now, the limit state design
method, based on the probability statistics and reliability analysis, is used world-
wide. In the meantime, the calculation method of the structural internal forces is
also developed from the classical elastic analysis into the ultimate equilibrium
methodconsideringplasticdeformation,andagainintothenon-linearanalysisalong
loadinghistory.Thecombinationofthefinite-elementanalysismethodandthecom-
puter technique is a very powerful means for accurate and quick analysis of a
complicated reinforced concrete structure and is widely used now in engineering
practice.
The progress of experimental method and high technicalities of experimental
equipmentandmeasuringinstrumentraisethecapabilityandaccuracyofstructural
testing.Variousenvironmentalandloadingconditionsofthestructurescanbesimu-
lated better and more and meticulous information and data can be obtained in the
testing. These are helpful for understanding correctly the responses of the testing
structure and discovering its newphysical phenomena andregularity.
All of these research achievements promote deeper understanding of the
behavior regularities of reinforced concrete materials and structures and raise the
4 CHAPTER 1 Introduction
technicallevelsofstructuraldesignandconstruction.So,reinforcedconcretestruc-
ture is developedcontinuously and will havewider prospects.
1.2 Characteristics of this course
Principle of Reinforced Concrete is a special textbook of the course for post-
graduatestudentsinstructuralengineeringandsimilar.Theyhavelearnedtheunder-
graduate courses of Basic Structural Members of Reinforced Concrete [0-5] and
Design Reinforced Concrete Structure and known the basic characteristics of rein-
forcedconcreteanditsdesignmethod.Thiscoursecontainsthemaintheoreticalba-
sis and experimental evidence for research and design of reinforced concrete
structure, and its contents and role are just like the course ‘Strength of Materials’
forthestructureofhomogeneouslinear-elasticmaterials.However,reinforcedcon-
creteismainlycomposedoftwomaterialsofdifferentproperties,i.e.reinforcement
and concrete, and concrete is an inhomogeneous and non-linear material and has
different values of compressive and tensile strengths. So, the mechanical behavior
of reinforced concrete is more varied and complicated, and the contents of this
course are more plentiful.
Reinforced concrete structure is a science branch of structural engineering and
certainlyfollowsthegeneralregularityofstructuralengineering.Varioustechnical
requirements and questions are often raised from engineering practice, and corre-
spondingsolutionsandmeasurementareobtainedbydifferentwayssuchassurvey
andstatistics,experimentalinvestigation,theoreticalanalysis,calculationandcom-
parison. After concluding the general variation regularity, revealing the working
mechanism, establishing the physical and mathematic models, and determining
thecalculationmethodandconstructionmeasures,theygobacktoengineeringprac-
tice and are demonstrated, improved, and complemented. Generally, after experi-
encing several cycles of practiceeresearchepractice, they will gradually approach
asatisfactory answer and finally servewell the engineering.
Since reinforced concrete is composed of two materials with considerably
different properties, it certainly has some particularities which distinguish from
the single material, e.g. steel or timber, used for the structure. Therefore, the
behaviorofreinforcedconcretedependsuponnotonlythepropertiesofthetwoma-
terials on their own, but also, to a greater extent, on the combination and relative
comparison ofthem, for example:
Differentformsofreinforcementelongitudinalortransverse,concentratedor
spread, over orunder-reinforced, natural orprestressed .
Relativevalueofbehaviorindicesofbothmaterialsestrengthratio,areaor
volumeratio, ratioofelasticmoduli,ratio ofcharacteristicstrains,differences
ofthermal strain, shrinkage, and creep ..
Therefore, the load-bearing capacity and deformation behavior of reinforced
concrete vary considerably. Sometimes, a special reinforced concrete can be
1.2 Characteristics of this course 5
designed and manufactured, using reasonably raw materials and proper reinforce-
mentform,tosatisfythetechnicalindiceswhichfittherequirementofaparticular
engineering project.
It is known that concrete is an inhomogeneous and non-linear composite mate-
rial, and its mechanical behavior is complicated and varied with time and its tech-
nical indices are scattered considerably. In addition, the combination of
reinforcement and concrete is of variform, this makes the mechanical behavior of
reinforcedconcretevarysignificantly.Uptonow,manyexperimentalandtheoretical
resultsofreinforcedconcretestructuralmembersundervariousloadingandenviron-
mentalconditionsareobtainedandcorrespondingcalculationmethodandstructural
detailingareestablishedandsatisfiedforengineeringpractice.However,thereisstill
nounifiedandaccuratetheoreticaltheoryandmethodforreinforcedconcreteunder
all situations.
Considering these characteristics of concrete material and reinforced concrete
structuralmembers, the following principlesare insisted uponin thisbook.
Basing on experimental evidencee Generally, the mechanical indices of
concrete material andbehaviorresponses of reinforced concrete structural
memberscanonlybedeterminedaccuratelyfromreasonableandcarefultests.
Therefore, acertainamountof experimental data are presented, thevariation
regularitiesare concluded,themechanismis analyzed,therationalknowledge
is summarized, the physical and mathematical models are established, and
finally, the experimental and engineering demonstrationsare performed.
Macroscopic mechanical responsee The microscopic analyses ofthe stress,
strain,andcrackofstructuralconcretearehardly reachedthe accurate results,
becauseofnon-uniformmicro-structure,localdefects,andscatteredbehaviorof
concrete material itself. Thebehaviorsof concrete materialand reinforced
concrete structure discussed inthis book representthe averagevalues ofthem
withinacertainscale(e.g.about(cid:2)70mm,or3or4timesthecoarseaggregate
size). It is accurate enough when theyare used inengineering practice.
RegularityandmechanismanalysisofmechanicalbehavioreThebehavior
responses ofconcrete materialand reinforced concretestructurevary consid-
erablyunder different loadingand environmental conditions, because ofthe
influences of various factors. However, the stress and deformation processes,
failurepattern,andultimatestrengthofthemstillpresentcertainregularities.It
ishopedtoanalyzetheirworkingmechanismsandtofindtheinherentessence
ofthemechanicalcharacteristicsofthestructure,whichisrelativelystableand
moreimportant.Incontrast,theparticularcalculationmethodandformulawill
be changed both inform andparameters, asthe experimental data are accu-
mulated,varied, or deleted.
Actual mechanicalbehavior and index e Theexperimental values and the
theoretical calculationvalues,listedin thisbook, for concrete materialand
reinforced concrete structuralmemberaregenerally the measuredor average
values. Thesevalues can be used for calculating the actual strengthand
6 CHAPTER 1 Introduction
deformationofthestructure.However,therearesystematicdifferencesbetween
thesevaluesandthecorrespondingnominalvaluesordesignvalues,whichare
used in the structuraldesign after considering the necessarysafetyofthe
structure. So, thesevalues have tobe convertedproperly andthen beused if
necessary.
Reflectingthe new research athome and abroade Reinforcedconcrete
structure andits materials developcontinuously, newexperiences are accu-
mulated and newquestions are raised inengineering practice, andrelevant
experimental and theoretical achievementsappear year after year.Thebasic
conceptandanalysismethodarerelativelystableandretainedinthisbook,and
thenewresearchresults,anddifferentacademicpointsofviewandmethod,are
contained.
Inaddition,thisbookmainlyservestheresearchandanalysisofreinforcedcon-
crete structure, the reinforcement and other structural detailing are, generally, not
stipulatedandtherequirementsofdesigncodearealsonotincluded.Whenaprac-
ticalquestioninthestructuralengineeringisdealtwith,therelevantliteraturesand
references, including the designcode, have tobe consulted.