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ÇOK KATLI YAPILARA GİRİŞÇOK KATLI YAPILARA GİRİŞÇOK KATLI YAPILARA GİRİŞÇOK KATLI YAPILARA GİRİŞ
İSTANBUL ÜNİVERSİTESİ
ÇOK KATLI YAPILARA GİRİŞÇOK KATLI YAPILARA GİRİŞÇOK KATLI YAPILARA GİRİŞÇOK KATLI YAPILARA GİRİŞ
Dr. Kağan YEMEZ
KY.IU2008@gmail.com
2
ÇOK KATLI YAPILARA GİRİŞÇOK KATLI YAPILARA GİRİŞÇOK KATLI YAPILARA GİRİŞÇOK KATLI YAPILARA GİRİŞ
İSTANBUL ÜNİVERSİTESİ
ÇOK KATLI YAPILARA GİRİŞÇOK KATLI YAPILARA GİRİŞÇOK KATLI YAPILARA GİRİŞÇOK KATLI YAPILARA GİRİŞ
Ders 4
�Döşeme sistemleri.–Betonarme – Çelik – Kompozit
–Tasarım kriterleri
3
İİç kolonların yerleri ç kolonların yerleri
betonarmebetonarme
çelikçelik
4
iç kolonların yerleriiç kolonların yerleri
Tali kiriTali kirişşlerler
Ana kiriAna kirişşbetonarmebetonarme
ÇelikÇelik
Tali kiriTali kirişşlerler
6 6 -- 22 m22 m
5
Structural Steelwork EurocodesStructural Steelwork EurocodesStructural Steelwork EurocodesStructural Steelwork Eurocodes
Introduction to composite Introduction to composite Introduction to composite Introduction to composite construction of buildingsconstruction of buildings
6
GeneralGeneralGeneralGeneral
These two materials complete one These two materials complete one
another:another:
SteelSteel and concreteand concrete
�� Concrete is efficient in compression and steel in Concrete is efficient in compression and steel in
tensiontensiontensiontension
�� Concrete encasement restrain steel against Concrete encasement restrain steel against
bucklingbuckling
�� Protection against corrosion and fireProtection against corrosion and fire
�� Steel bring ductility into the structureSteel bring ductility into the structure
7
GeneralGeneralGeneralGeneral
Aspects for using composite Aspects for using composite structures:structures:
�� ArchitecturalArchitectural�� ArchitecturalArchitectural
�� EconomicalEconomical
�� FunctionalityFunctionality
�� Service and FlexibilityService and Flexibility
�� AssemblyAssembly
8
Aspects for using composite Aspects for using composite
structuresstructures
Aspects for using composite Aspects for using composite
structuresstructures
Architectural:Architectural:
�� Longer spansLonger spans
�� Thinner slabsThinner slabs
�� More slender columnMore slender column
�� More generous opportunities for More generous opportunities for
designdesign
9
Aspects for using composite Aspects for using composite
structuresstructures
Aspects for using composite Aspects for using composite
structuresstructures
Economical:Economical:�� Reduction of height reduces the total of Reduction of height reduces the total of
the building the building ----> saving area of cladding> saving area of cladding
�� Longer spans with the same height Longer spans with the same height
----> column free rooms> column free rooms----> column free rooms> column free rooms
�� Additional storeys with the same Additional storeys with the same
total height of buildingtotal height of building
�� Quicker time of erection:Quicker time of erection:
�� Saving costs, earlier completion of the buildingSaving costs, earlier completion of the building
�� Lower financing costsLower financing costs
�� Ready for use earlier thus increasing Ready for use earlier thus increasing
rental incomerental income
10
Aspects for using composite Aspects for using composite
structuresstructures
Aspects for using composite Aspects for using composite
structuresstructures
Functionality:Functionality:
�� Fire protection by using principles of reinforced Fire protection by using principles of reinforced
concrete in which the concrete protects the steelconcrete in which the concrete protects the steel
11
Aspects for using composite Aspects for using composite
structuresstructures
Aspects for using composite Aspects for using composite
structuresstructures
Service and building flexibility:Service and building flexibility:
�� Adaptable structuresAdaptable structures
�� Modification during the life of the buildingModification during the life of the building
�� Modify services without violating the privacy of Modify services without violating the privacy of
other occupantsother occupants
�� Accommodation of service facilitiesAccommodation of service facilities
in the ceilingin the ceiling
within a false floorwithin a false floor
in a coffer box running along the wallsin a coffer box running along the walls
12
Aspects for using composite Aspects for using composite
structuresstructures
Aspects for using composite Aspects for using composite
structuresstructures
Assembly:Assembly:�� Working platforms of steel deckingWorking platforms of steel decking
�� Permanent shuttering Permanent shuttering
�� Reinforcement of profiled steel sheetings Reinforcement of profiled steel sheetings �� Reinforcement of profiled steel sheetings Reinforcement of profiled steel sheetings
�� Speed and simplicity of constructionSpeed and simplicity of construction
�� Quality controlled products ensure greater accuracyQuality controlled products ensure greater accuracy
13
Construction methodsConstruction methodsConstruction methodsConstruction methods
Traditionally two counteracting methods of
construction could be observed both connected with
special advantages but also disadvantages worth
mentioning.�� Conventional concrete Conventional concrete
construction methodconstruction method
�� Construction in steelConstruction in steel
construction methodconstruction method
++ freedom of form and freedom of form and
shapesshapes
++ easy to handleeasy to handle
++ thermal resistancethermal resistance
-- timetime--consuming shutteringconsuming shuttering
-- sensitive on tensile forcessensitive on tensile forces
++ high ratio between bearing high ratio between bearing
capacity and weightcapacity and weight
++ prefabricationprefabrication
++ high accuracy high accuracy
-- low fire resistancelow fire resistance
-- need of higher educated need of higher educated
personalpersonal
14
Construction methodsConstruction methodsConstruction methodsConstruction methods
�� Composite ConstructionComposite Construction
comparing these two methods a combination of both comparing these two methods a combination of both
presents the most economic waypresents the most economic way
++ higher bearing capacityhigher bearing capacity++ higher bearing capacityhigher bearing capacity
++ higher stiffness higher stiffness
++ plastic redistributionplastic redistribution
15
Construction elementsConstruction elementsConstruction elementsConstruction elements
composite column floor = beam + slabcomposite beam
composite slab
16
Construction elementsConstruction elementsConstruction elementsConstruction elements
Composite slabsComposite slabs
��Reinforced concrete slabReinforced concrete slab
in-situ concrete on shuttering partially prefabricated slabs fully prefabricated slabs
17
Construction elementsConstruction elementsConstruction elementsConstruction elements
SlabsSlabs
��PrePre--stressed concrete slabsstressed concrete slabs
18
Construction elementsConstruction elementsConstruction elementsConstruction elements
SlabsSlabs
��Profile steel sheetingProfile steel sheeting
Interlock between steel and concreteInterlock between steel and concrete
frictionalfrictionalmechanicalmechanical
end anchorageend anchorage
19
Composite slabs comprise ofComposite slabs comprise ofComposite slabs comprise ofComposite slabs comprise of
in-situ concrete slab
reinforcement
Support beam
• steel decking
• reinforcement
• cast in situ concrete
After concrete has Support beam
After concrete has hardened:
behaves as a composite steel-concrete structural element
Profiled steel designed to act as both permanent formwork during concreting and tension reinforcement
After construction:
• profiled steel sheet
• upper concrete topping
interconnected so that horizontal shear forces can be transferred at the steel-concrete interface.
20
Profiled decking typesProfiled decking typesProfiled decking typesProfiled decking types
Numerous types with different: • shapes• depth and distance between ribs• width, lateral covering, • plane stiffeners • mechanical connections • mechanical connections Thickness : 0,75mm � 1,5mm Depth : 40mm � 80mmGalvanized on both facesCold formedCold forming causes strain
(pekleşme) hardening and increase in yield
S235 � 300 N/mm2
21
Steel to concrete connectionSteel to concrete connectionSteel to concrete connectionSteel to concrete connection
• Adhesion not sufficient to
create composite action in
the slab
Efficient connection made by:
• Mechanical anchorage from
re-entrant trough profile
bo
bb
hc
hph
Open trough profile
bo
bb
hc
hph
• Mechanical anchorage from
local deformations
• Decking shape - re-entrant
trough profile
• End anchorage provided by
welded studs
• End anchorage by
deformation of the ribs at the end of the sheeting.
( a ) mechanical anchorage ( c ) end anchorage
( b ) frictional interlock ( d ) end anchorage by deformation
22
Construction elementsConstruction elementsConstruction elementsConstruction elements
BeamsBeams��Conventional and innovative Conventional and innovative
composite beamscomposite beams
23
Construction elementsConstruction elementsConstruction elementsConstruction elements
BeamsBeams
��Types of shear connectorsTypes of shear connectors
24
Composite actionComposite actionComposite actionComposite action
25
Döşemeler : yerinde dökme Döşemeler : yerinde dökme
betonarme Döşemelerbetonarme Döşemeler
26
BaBaşşlıklı kamalarınlıklı kamalarınkaynaklanmasıkaynaklanması
27
MetalMetaltrapeztrapeztrapeztrapezperdeperde
28
Ters SehimTers Sehim
29
Progress factor: steel gradesProgress factor: steel gradesProgress factor: steel gradesProgress factor: steel grades
Advantages of mixed construction and high steel grades
Type ofconstruction
non-mixed mixed mixed mixed
Steel grade S 235 S 235 S 355 S 460
Reduction in
weight of steel- 13 % 44 % 52 %
Cross-section
Beam Size HE 650 A HE 550 A IPE 550 IPE 500
Reduction in
weight of steel- 13 % 44 % 52 %
30
Construction elementsConstruction elementsConstruction elementsConstruction elements
ColumnsColumns
��Examples of composite columnsExamples of composite columns
31
Construction elementsConstruction elementsConstruction elementsConstruction elements
JointsJoints��Example of vertical shear transfer Example of vertical shear transfer
between beam and columnbetween beam and column
removed after concretingreinforcement
bracket for the lower flange
bracket with shear connectorscontact pieceweld seam
shot-fired nails
32
ExamplesExamplesExamplesExamples
Millennium Tower Millennium Tower (Vienna (Vienna -- Austria)Austria)
�� 55 storeys55 storeys
�� Total height 202 mTotal height 202 m
Total ground floor 38000 m2Total ground floor 38000 m2�� Total ground floor 38000 m2Total ground floor 38000 m2
�� Capital expenditure about 145 million EuroCapital expenditure about 145 million Euro
�� Time of erection: 8 monthsTime of erection: 8 months
33
ExamplesExamplesExamplesExamples
Millennium Tower Millennium Tower (Vienna (Vienna -- Austria)Austria)
42,3 m42,3 m
Composite columns
Concrete core
Composite Slim floor beams
Concrete slab
Composite frame
34
ExamplesExamplesExamplesExamples
Millennium Tower Millennium Tower (Vienna (Vienna -- Austria)Austria)
Total time of erection: 8 monthTotal time of erection: 8 monthmax. speed 2 to 2.5 storeys per week!max. speed 2 to 2.5 storeys per week!
35
ExamplesExamplesExamplesExamples
Citibank Duisburg Citibank Duisburg (Duisburg (Duisburg -- Germany)Germany)
�� 15 storeys15 storeys
�� Total height 72 mTotal height 72 m
�� Total ground floor 14500 m2Total ground floor 14500 m2
36
ExamplesExamplesExamplesExamples
Parking deck “DEZ” Parking deck “DEZ” (Innsbruck (Innsbruck -- Austria)Austria)
�� 4 storeys4 storeys
�� Ground dimensions 60 x 30 mGround dimensions 60 x 30 m
�� Max. span length 10.58 m with Max. span length 10.58 m with 26 cm slim floor slab (= l/40)26 cm slim floor slab (= l/40)26 cm slim floor slab (= l/40)26 cm slim floor slab (= l/40)
37
ExamplesExamplesExamplesExamples
Parking deck “DEZ” Parking deck “DEZ” (Innsbruck (Innsbruck -- Austria)Austria)
Erection of composite columns over 2 storeysErection of composite columns over 2 storeysAssembly of prefabricated concrete slabsAssembly of prefabricated concrete slabs
38
ExamplesExamplesExamplesExamples
Parking deck “DEZ” Parking deck “DEZ” (Innsbruck (Innsbruck -- Austria)Austria)
260 200
Cross section of the slimCross section of the slim--floor beam and slabfloor beam and slab--200 mm concrete slab200 mm concrete slab--60 mm prefabricated concrete elements60 mm prefabricated concrete elements--steel beam:steel beam: web 165/20 mmweb 165/20 mm
flange 245/40 mmflange 245/40 mm--headed studs: 22 mmheaded studs: 22 mm
60
39
Concluding summaryConcluding summaryConcluding summaryConcluding summary
Composite construction is popular Composite construction is popular for buildings because of following for buildings because of following aspects:aspects:
�� EconomyEconomy
�� ArchitectureArchitecture
�� FunctionalityFunctionality
�� Service and building flexibilityService and building flexibility
�� AssemblyAssembly
40
ÇOK KATLI YAPILARA GİRİŞÇOK KATLI YAPILARA GİRİŞÇOK KATLI YAPILARA GİRİŞÇOK KATLI YAPILARA GİRİŞ
İSTANBUL ÜNİVERSİTESİ
ÇOK KATLI YAPILARA GİRİŞÇOK KATLI YAPILARA GİRİŞÇOK KATLI YAPILARA GİRİŞÇOK KATLI YAPILARA GİRİŞ
Dr. Kağan YEMEZ
KY.IU2008@gmail.com
Next … Introduction to EC 4
41
Structural Steelwork EurocodesStructural Steelwork EurocodesStructural Steelwork EurocodesStructural Steelwork Eurocodes
Introduction to EC4Introduction to EC4
42
Eurocode 4 Part 1.1Eurocode 4 Part 1.1Eurocode 4 Part 1.1Eurocode 4 Part 1.1
�Sections follow a typical design sequence:– Material properties (Malzeme özellikleri)
– Safety factors (Emniyet katsayıları)
– Methods of analysis
– Element design, ultimate and serviceability
�Some sections deal with specific topics:-– Durability
– Composite joints in frames for buildings
– Composite slabs with profiled steel sheeting
43
TerminologyTerminologyTerminologyTerminology
� A number of terms are clearly defined:– ‘COMPOSITE MEMBER’ - one with concrete and steel
interconnected components
• ‘BEAM’ - subject mainly to bending (eğilme)
• ‘COLUMN’ - subject mainly to compression• ‘COLUMN’ - subject mainly to compression
(basınç)
• ‘SLAB’ - profiled steel sheets as permanent
shuttering (kalıcı kalıp) and tensile reinforcement
(çekme donatısı)
– ‘SHEAR CONNECTION’ (kayma donatısı) - the connection between steel and concrete components
44
TerminologyTerminologyTerminologyTerminology
� ‘COMPOSITE FRAME’ - includes some composite
elements
� ‘COMPOSITE JOINT’ - reinforcement contributes to
resistance (dayanım) and stiffness (rijitlik). resistance (dayanım) and stiffness (rijitlik).
� ‘PROPPED (ALTTAN DESTEKLİ) STRUCTURE OR
MEMBER’ - weight of wet concrete carried
independently, or steel supported until concrete able
to resist stress
� ‘UNPROPPED (ALTTAN DESTEKSİZ) STRUCTURE
OR MEMBER’ - weight of wet concrete is applied to
the steel elements unsupported in the span.
45
Material PropertiesMaterial PropertiesMaterial PropertiesMaterial Properties
�Concrete– Normal and lightweight concrete as EC2
– Concrete grades less than C20/25 or greater than C60/75 excludedexcluded
�Reinforcing steel– As EC2
– Reinforcement grades with a characteristic strength greater than 550N/mm2 not covered
46
Material PropertiesMaterial PropertiesMaterial PropertiesMaterial Properties
�Structural steel– As EC3
– Steel grades with a characteristic strength greater than 460N/mm2 not covered
�Profiled steel sheeting for composite slabs�Profiled steel sheeting for composite slabs– As EC3
– Types of steel restricted
– Recommended minimum thickness is 0.7mm
�Shear connectors– Reference to ENs for material specification
47
Structural AnalysisStructural AnalysisStructural AnalysisStructural Analysis
�Ultimate Limit State (Taşıma Gücü)– Elastic or plastic global analysis allowed
– Certain conditions apply to the use of plastic analysis
�Serviceability Limit State (Servis Yüklemesi)– Elastic analysis must be used
– The effective width is as defined for the ultimate limit state, and appropriate allowances may be made for concrete cracking, creep and shrinkage
48
Elastic AnalysisElastic AnalysisElastic AnalysisElastic Analysis
� Stages of construction may need to be considered
� The stiffness of the concrete may be based on the
uncracked condition for braced structure
� In other cases, some account may need to be taken
of concrete cracking by using a reduced stiffness over
a designated length of beam
� Creep is accounted for by using appropriate values
for the modular ratio
� Shrinkage and temperature effects may be ignored
� Some redistribution of elastic bending moments is
allowed
49
Ultimate Limit StateUltimate Limit State
(Taşıma Gücü)(Taşıma Gücü)
Ultimate Limit StateUltimate Limit State
(Taşıma Gücü)(Taşıma Gücü)
�Concerned with the resistance of the structure to collapse
�Based on the strength of individual �Based on the strength of individual elements
�Overall stability of the structure must be checked
�Factored load conditions
50
BeamsBeamsBeamsBeams
�Bending resistance– Applicability of plastic, non-linear and elastic
analysis
– Full or partial interaction defined
�Vertical shear resistance– Effects of shear buckling
– Combined bending and shear
51
LateralLateral--Torsional BucklingTorsional Buckling
(Yanal Burulması Burkulma )(Yanal Burulması Burkulma )
LateralLateral--Torsional BucklingTorsional Buckling
(Yanal Burulması Burkulma )(Yanal Burulması Burkulma )
�Top flange is laterally restrained by the
concrete slab
� In hogging bending the compression flange is � In hogging bending the compression flange is
not restrained– Lateral-torsional buckling must be checked
– Under certain conditions such checks are unnecessary
52
Longitudinal Shear ConnectionLongitudinal Shear ConnectionLongitudinal Shear ConnectionLongitudinal Shear Connection
�Related to:– strength of slab and transverse reinforcement
– connector types– connector types
53
Serviceability Limit StateServiceability Limit State
(Servis Yüklemesi)(Servis Yüklemesi)
Serviceability Limit StateServiceability Limit State
(Servis Yüklemesi)(Servis Yüklemesi)
�Deflections
�Concrete cracking
�Control of vibrations and limiting �Control of vibrations and limiting stresses are not included
54
DeflectionsDeflections
(Sehim)(Sehim)
DeflectionsDeflections
(Sehim)(Sehim)
�Calculated deflection is seldom meaningful because:
– actual load unlike design load;– actual load unlike design load;
– idealised support conditions seldom realised
�But calculated deflection can provide an index of stiffness
55
DeflectionsDeflectionsDeflectionsDeflections
�Guidance is given on calculating deflections for composite beams– including allowances for partial interaction– including allowances for partial interaction
– concrete cracking
�Calculated deflections should be compared with limits in Eurocode 3 or in given standards.
56
Deflection LimitsDeflection LimitsDeflection LimitsDeflection Limits
�Six categories:– roofs generally
– roofs frequently carrying personnel other than for maintenance
– floors generally
– floors and roofs supporting plaster or other brittle finish or non-– floors and roofs supporting plaster or other brittle finish or non-flexible partitions
– floors supporting columns (unless deflection included in global analysis for ultimate limit state)
– situations in which the deflection can impair the appearance of the building
57
Calculating DeflectionsCalculating DeflectionsCalculating DeflectionsCalculating Deflections
�Steel member alone– Construction stage for for unpropped conditions
– Procedures of EC3
– Bare steel section properties
�Composite cross-section– Elastic analysis
– Suitable transformed section
– Allow for incomplete interaction and cracking of
concrete where appropriate
58
Concrete CrackingConcrete CrackingConcrete CrackingConcrete Cracking
�Concrete may crack due to:– Direct loading
– Shrinkage– Shrinkage
�Excessive cracking of the concrete can:– affect durability
– compromise appearance
– impair the proper functioning of the building
59
Concrete CrackingConcrete CrackingConcrete CrackingConcrete Cracking
� May not be critical issues
� Simplified approaches based on:
– minimum reinforcement ratios– minimum reinforcement ratios
– maximum bar spacing
– diameters
� Guidance on calculating crack widths
� Limiting crack widths related to exposure
conditions
60
Composite SlabsComposite SlabsComposite SlabsComposite Slabs
�Ultimate and serviceability limit states
�Construction stage– steel sheeting acts as permanent shuttering– steel sheeting acts as permanent shuttering
– must support wet concrete loads (unpropped)
– reference to EC3 Part 1.3
61
Composite SlabsComposite SlabsComposite SlabsComposite Slabs
�Calculation procedures for– flexure
– longitudinal shear– longitudinal shear
– vertical shear
– stiffness
– span:depth ratios
– limiting
62
Concluding SummaryConcluding SummaryConcluding SummaryConcluding Summary
� A number of terms in EC4 have a very precise
meaning
� The principal components for composite
construction are concrete, reinforcing steel,
structural steel, profiled steel sheet, and shear structural steel, profiled steel sheet, and shear
connectors
� Material properties for each component are
defined in other Eurocodes
� Guidance is given on what methods of analysis,
both global and cross-sectional, are appropriate
63
Concluding SummaryConcluding SummaryConcluding SummaryConcluding Summary
� EC4 is based on limit state design principles
� The Ultimate Limit State is concerned with
collapse (Taşıma gücü göçme ile ilgili)
� The Serviceability Limit State is concerned with The Serviceability Limit State is concerned with
operational conditions. (Servis Yüklemesi kullanım koşullarında)These relate specifically
to deflections and crack control, and EC4
provides guidance for controlling both
� EC4 is structured on the basis of element type;
detailed procedures for the design of beams,
columns and slabs are given in separate
sections.
64
Structural Steelwork EurocodesStructural Steelwork EurocodesStructural Steelwork EurocodesStructural Steelwork Eurocodes
Structural Modelling and DesignStructural Modelling and DesignStructural Modelling and DesignStructural Modelling and Design
65
Scope of the lectureScope of the lectureScope of the lectureScope of the lecture
�Structural modelling
�The design process�The design process
�Generalities about design requirements for main structural elements
66
Structural modellingStructural modellingStructural modellingStructural modelling
In order to overcome this difficulty:
– The slab is assumed to span in a principal direction and is designed
accordingly.
– The three-dimensional framework is then reduced to plane frames
which are studied independently each from the other.
– In order to enable such a “dissociation” into plane frames, the concept – In order to enable such a “dissociation” into plane frames, the concept
of effective width for the composite slabs is introduced.
Sonuç olarak, kompozit kiriş çelik profil ve etkilidöşeme tablasından oluşur ve birbirine kaymabirleşim elemanları ile bağlanır.
(continued)
67
Structural modellingStructural modellingStructural modellingStructural modelling
Effective width of slab
« Shear lag » effects induce non uniform stress distribution in the slab
⇒ concept of “effective width” b⇒ concept of “effective width” beff
(continued)
b b b
be1be2
beff
211
68
Structural modellingStructural modellingStructural modellingStructural modelling
Simple and safe recommendations in Eurocode 4:
beff = be1 + be2
with bei = min ( Lo/8; bi )
where L is the distance measured between consecutive where Lo is the distance measured between consecutive points of contraflexure in the bending moment diagram
(continued)
0,25(L + L ) 1 2 1,5L but 4 < L +0,5L )4 3 L = 0
L = 0 0,8L 1 0,7L 2 0,8L - 0,3L but > 0,7L
3 4 3
L 1 L 2 L 3 L 4
0,25(L + L ) 2 3
69
Structural modellingStructural modellingStructural modellingStructural modelling
Equivalent modular ratio n
Actual composite beam cross-section replaced by an
equivalent steel section for elastic calculations.
Use of an « equivalent modular ratio n » Use of an « equivalent modular ratio n »
Ea is the elastic modulus for steel
E’c is an elastic « effective »modulus for concrete
(continued)
'c
a
E
En=
70
Structural modellingStructural modellingStructural modellingStructural modelling
The transformed section
(continued)
71
Structural modellingStructural modellingStructural modellingStructural modelling
Elastic strains and stresses in the composite section
(continued)
72
Structural modellingStructural modellingStructural modellingStructural modelling
The E’c value is influenced by:
– the concrete grade
– the concrete age,
– the short-term or long-term character of the loading
⇒Effects of creep, shrinkage, …⇒Effects of creep, shrinkage, …
Values of E’c ond of the modular ratio n are
given in the next slide.
(continued)
73
Analysis for ultimate limit statesAnalysis for ultimate limit statesAnalysis for ultimate limit statesAnalysis for ultimate limit states
�Rough values of E’c for evaluation of n
– E’c = Ecm for short-term effects
– E’c = Ecm / 3 for long-term effects– E’c = Ecm / 3 for long-term effects
(continued)
Strength class
of concrete
20/25 25/30 30/37 35/45 40/50 45/55 50/60
Ecm (kN/mm2) 29 30,5 32 33,5 35 36 37
74
Design requirementsDesign requirementsDesign requirementsDesign requirements
�Design requirements at SLS
– Control of:
� the transverse displacements of the composite � the transverse displacements of the composite
beams
� the cracking of the concrete
� the beam vibrations, especially for large span
beams
(continued)
75
Design requirementsDesign requirementsDesign requirementsDesign requirements
� Design requirements at ULS
– Verification of the joint resistance
– Verification of the slab resistance– Verification of the slab resistance
– Verification of the column stability and resistance
– Verification of the composite beams
(specific design checks listed on next slides)
(continued)
76
Design requirementsDesign requirementsDesign requirementsDesign requirements
– Specific design checks for composite beams
� Resistance of critical sections defined as the points of :
� maximum bending moment (section I-I)
� maximum shear (section II-II at external supports)
� high combined bending moment and shear (sections III-III)
� sudden change of section and/or mechanical properties
P
splice
II
II
I
I
III III
III III
V
V V
IV
VI
VI
d
� sudden change of section and/or mechanical properties
(continued)
77
Design requirementsDesign requirementsDesign requirementsDesign requirements
– Specific design checks for composite beams
� The strength of the longitudinal shear connection (line IV-IV)
� The longitudinal shear strength of the transversally reinforced concrete slab (line V-V and VI-VI)
� The resistance to lateral-torsional buckling under negative bending
P
splice
II
II
I
I
III III
III III
V V
IV
VI VI
VI VI
VII
d
� The resistance to lateral-torsional buckling under negative bending moments, with lateral displacement of the bottom flange of the steel section (buckled position VII)
78
Composite Slabs Composite Slabs
with with
Profiled Steel SheetingProfiled Steel Sheeting
Structural Steelwork EurocodesStructural Steelwork Eurocodes
Profiled Steel SheetingProfiled Steel Sheeting
79
Composite slabsComposite slabsComposite slabsComposite slabs
• One way spanning
• Typical span 3.5 m
• Span onto composite secondary
beams beams
• Secondary beams span onto primary
beams
• Rectangular grids
• Slab unsupported during construction
80
Advantages of composite slabsAdvantages of composite slabsAdvantages of composite slabsAdvantages of composite slabs
• hızlı ve basit inşaat
• aşağı katta çalışan işçileri koruyan güvenli
çalışma platformu
• betonarme döşemeden daha hafif• betonarme döşemeden daha hafif
• Genellikle hafif beton ile kullanılır
- Zati ağırlığı azaltmak için
• fabrikada prefabrik hazırlanabilen döşeme
saçları ve kirişleri
- küçük toleranslarla bile çalışılabilir.
81
Composite slabs comprise ofComposite slabs comprise ofComposite slabs comprise ofComposite slabs comprise of
in-situ concrete slab
reinforcement
Support beam
• steel decking
• reinforcement
• cast in situ concrete
After concrete has Support beam
After concrete has hardened:
behaves as a composite steel-concrete structural element
Profiled steel designed to act as both permanent formwork during concreting and tension reinforcement
After construction:
• profiled steel sheet
• upper concrete topping
interconnected so that horizontal shear forces can be transferred at the steel-concrete interface.
82
Profiled decking typesProfiled decking typesProfiled decking typesProfiled decking types
Numerous types with different: • shapes• depth and distance between ribs• width, lateral covering, • plane stiffeners • mechanical connections • mechanical connections Thickness : 0,75mm � 1,5mm Depth : 40mm � 80mmGalvanized on both facesCold formedCold forming causes strain
(pekleşme) hardening and increase in yield
S235 � 300 N/mm2
83
Steel to concrete connectionSteel to concrete connectionSteel to concrete connectionSteel to concrete connection
• Adhesion not sufficient to
create composite action in
the slab
Efficient connection made by:
• Mechanical anchorage from
re-entrant trough profile
bo
bb
hc
hph
Open trough profile
bo
bb
hc
hph
• Mechanical anchorage from
local deformations
• Decking shape - re-entrant
trough profile
• End anchorage provided by
welded studs
• End anchorage by
deformation of the ribs at the end of the sheeting.
( a ) mechanical anchorage ( c ) end anchorage
( b ) frictional interlock ( d ) end anchorage by deformation
84
Reinforcement in the slabReinforcement in the slabReinforcement in the slabReinforcement in the slab
Provided for:
• Load distribution of line or
point loads
• Local reinforcement of slab
openingsopenings
• Fire resistance
• Upper reinforcement in
hogging moment area
• Control cracking due to shrinkage
Mesh reinforcement
placed at the top of the profiled decking ribs.
85
Design requirementsDesign requirementsDesign requirementsDesign requirements
Overall depth h, > 80 mm.
Thickness hc of concrete
over decking > 40mm
If the slab acts compositely
• The nominal size of
aggregate should not
exceed the least of:
0,40 hc or bo/3 or 31,5 mm
• Composite slabs require a If the slab acts compositely
with a beam, or is used as
a diaphragm
total depth h > 90mm
concrete thickness hc > 50mm
• Composite slabs require a
minimum bearing of
75mm for steel or
concrete and 100mm for other materials.
re-entrant trough profile
bo
bb
hc
hph
Open trough profile
bo
bb
hc
hph
86
Composite slab behaviourComposite slab behaviourComposite slab behaviourComposite slab behaviour
Perfect connection
between the concrete
and steel sheet -
complete interaction.
Phchp
P
L =L
4s L =L4s
b
ht
Relative longitudinal
displacement between
steel sheet and adjacent
concrete- incomplete
interaction.
L
L =4s L =
4s
load P
Pu
Pf
0deflection δ
First crack load
P : complete interactionu
P : partial interactionu
P : no interactionu
P P
δ
load P
Pu
Pf
First crack load
P : complete interactionu
P : partial interactionu
P : no interactionu
P P
δ
87
Composite slab stiffnessComposite slab stiffnessComposite slab stiffnessComposite slab stiffness
After first cracking,
frictional and mechanical
interaction begin to
develop as the first micro-slips occur.
0deflection δ
First crack load
Stiffness depends on the
effectiveness of the connection type.
From 0 to Pf , the physical-
chemical phenomena
account for most of the
initial interaction between the steel and concrete.
88
Three types of behaviourThree types of behaviourThree types of behaviourThree types of behaviour
Complete interaction:
• No global slip at the
steel-concrete interface
exists
• Failure can be brittle or
load P
Pu
Pf
First crack load
P : complete interactionu
P : partial interactionu
P : no interactionu
P P
δ
• Failure can be brittle or
ductile
Zero interaction:
• Global slip at the steel-
concrete interface is not
limited and there is almostno transfer of shear force.
0deflection δ
First crack load
Partial interaction:
• Global slip not zero but limited
• Shear force transfer partial and
the ultimate lies between the
ultimate loads of the previous
cases.• Failure can be brittle or ductile.
89
Composite slab stiffnessComposite slab stiffness
• Represented by the first part of the P-δ curve
• Stiffness highest for complete interaction
• Three types of link between steel and concrete:
1. Physical-chemical link:1. Physical-chemical link:
always low but exists for all profiles
2. Friction link:
develops as soon as micro slips appear
3. Mechanical anchorage link:
acts after the first slip
depends on the steel-concrete interface shape.
90
Composite slab collapse modesComposite slab collapse modesComposite slab collapse modesComposite slab collapse modes
Failure type I
applied moment exceeds Mpl.Rd
generally the critical mode for moderate to highgenerally the critical mode for moderate to high
spans with a high degree of interaction
between the steel and concrete.
III I
II
Shear span Ls
91
Composite slab collapse modesComposite slab collapse modesComposite slab collapse modesComposite slab collapse modes
Failure type II
ultimate load resistance is governedby the steel concrete interface.by the steel concrete interface.
happens in section II along the shear span Ls.
III I
II
Shear span Ls
92
Composite slab collapse modesComposite slab collapse modesComposite slab collapse modesComposite slab collapse modes
Failure type III
applied vertical shear exceeds shearresistance.resistance.
This is only likely to be critical for deep slabsover short spans and subject to heavy loads
III I
II
Shear span Ls
93
Brittle Brittle or or ductile failure?ductile failure?Brittle Brittle or or ductile failure?ductile failure?
• Depends on
characteristics of the steel-
concrete interface.
• Slabs with open trough
profiles experience a more
Load PDuctile behaviour
profiles experience a more
brittle behaviour
• Slabs with re-entrant
trough profiles tend to
exhibit more ductile
behaviour.
deflection δ
Brittle behaviour
• Decking producers ameliorate
brittle behaviour with various
mechanical means – embossments,
indentations, dovetails
Shear connectors
between beam and
slab influence the failure mode.
94
Design conditionsDesign conditionsDesign conditionsDesign conditions
Two design conditions should to be
considered
During construction
steel sheet acts as
shuttering
In service
concrete and steel combine to
form a single composite unitshuttering form a single composite unit
95
Construction conditionConstruction conditionConstruction conditionConstruction condition
• Steel deck must resist weight of wet concrete
and the construction loads
• Deck may be propped temporarily during
constructionconstruction
• Preferable if no propping is used
• Verification at ULS and SLS should be in
accordance with part 1.3 of Eurocode 3
• Effects of embossments or indentations on
the design resistances should be considered
96
Design (construction) at the ULSDesign (construction) at the ULSDesign (construction) at the ULSDesign (construction) at the ULS
• Weight of concrete and steel deck
• Construction loads
- weight of the operatives and concreting plant
• ‘Ponding' effect
- increased depth of concrete due to deflection• Storage load (if any)• Storage load (if any)
( b ) ( b )( a ) ( c )
3000
( b ) ( b )( a ) ( c )
3000
moment over supportMoment in mid-span
( a ) Concentration of construction loads 1,5 kN / m²
( b ) Distributed construction load 0,75 kN / m²
( c ) Self weight
! Minimum values are
not necessarily
sufficient for excessive
impact or heaping
concrete, or pipeline or
pumping loads
97
Deflection Deflection Deflection Deflection
Under self weight + the weight of wet concrete,
but excluding construction loads
δ < L/180
If δ < 1/10 of the slab depthIf δ < 1/10 of the slab depth
- ponding effect may be ignored
Allow for ponding by assuming in design
- nominal thickness of the concrete is
increased over the whole span by 0,7δ.
98
Composite slab design checksComposite slab design checksComposite slab design checksComposite slab design checks
Loads to be considered are the following :
1. Self-weight of the slab (profiled sheeting and
concrete)
2. Other permanent self-weight loads (not load
carrying elements)
3. Reactions due to the removal of the possible
propping
4. Live loads
5. Creeping, shrinkage and settlement
6. Climatic actions (temperature, wind...).
For typical buildings, temperature variations are generally not considered.
99
Serviceability limit stateServiceability limit stateServiceability limit stateServiceability limit state
1. Deflections
2. Slip between the concrete slab and the
decking at the end of the slab called end slip3. Concrete cracking
100
DeflectionsDeflectionsDeflectionsDeflections
Recommended limiting values
• L/250 permanent + variable long duration loads
• L/300 variable long duration loads
• L/350 if composite slab supports brittle elements
Deflection of the sheeting due to its own weight and
the wet concrete need not be included
101
SummarySummarySummarySummary
• Composite slabs are widely used in steel framed
buildings
• Steel deck acts as
- shuttering during construction
- steel reinforcement for the concrete slab. - steel reinforcement for the concrete slab.
• Design of composite slabs requires
consideration of two conditions
1. steel deck as a relatively thin bare steel
section supporting wet concrete and
construction operatives
2. as a composite structural element in service
102
SummarySummarySummarySummary
• Performance of a composite slab is
dependent on the effectiveness of the shear
connection between the concrete and steel
sheeting.
• Longitudinal shear resistance may be
assessed by:
1. A semi-empirical design method (m-k)
2. Partial interaction theory
103
ÇOK KATLI YAPILARA GİRİŞÇOK KATLI YAPILARA GİRİŞÇOK KATLI YAPILARA GİRİŞÇOK KATLI YAPILARA GİRİŞ
İSTANBUL ÜNİVERSİTESİ
ÇOK KATLI YAPILARA GİRİŞÇOK KATLI YAPILARA GİRİŞÇOK KATLI YAPILARA GİRİŞÇOK KATLI YAPILARA GİRİŞ
Dr. Kağan YEMEZ
KY.IU2008@gmail.com
Next…Shear Connectors and Structural Analysis
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