Behaviour of steel concrete composite beams made of ultra high performance concrete

FE Finite ElementFEA Finite Element Analysis FEM Finite Element Methods NFEA Nonlinear Finite Element Analysis FES Finite Element Simulation FEMD Finite Element Modelling SG Strain gauge

Composite Beams Made of Ultra High Performance Concrete

der Universit¨ at Leipzig

DISSERTATION

zur Erlangung des akademischen Grades

Doktor-Ingenieur (Dr.-Ing.)

vorgelegt von

M.Eng Bui Duc Vinh

geboren am 07 April 1972 in Vinh Phuc - Vietnam

Leipzig, 9th October 2010

This thesis was the results of a long hard working period of the author, is wouldnot have been possible without the contribution of a great number of people:First of all, I would like to thank to my supervisor Prof Dr.-Ing habil NguyenViet Tue for giving me the opportunity to join his research group and giving methis challenging research project I had learn a lot of thing from many hoursdiscussion with him He was not only always able to push up my spirits while Iwas in despair with my results but also sharing with me in sad moment which Ihad spent, and I am very grateful for that.

The experiments of this study could not have been performed without the helpand technical expertise of the laboratory personnel, as of Dipl.-Ing Holger Busch,Dipl.-Ing Immanuel Wojan and many staffs at MFPA-Leipzig for conducting theexperiments I would like to express my thanks for their support

My gratitude also goes to Dr.-Ing Nguyen Duc Tung, Dr.-Ing Jiaxin Ma,Dr.-Ing Michael K¨uchler, Dipl.-Ing Jiabin Li, Dipl.-Ing Stephan Mucha, Dipl.-Ing Gunter Schenck etc my colleagues in IMB (Institut f¨ur Massivbau undBaustofftechnologie, Uni-Leipzig) for many valuable suggestions and discussionhours Grateful appreciation is also due to Mrs Sigrid Fritzsche and Mrs SylviaProksch for their warm friendship and constant help during my stay in Leipzig

I wish to thank the German Research Foundation (DFG- Deutsche gemeinschaft) for finance support the research project SPP 1182, which allows

Forschungs-me take up doctoral studies at University of Leipzig, Germany

Last but not least, I want to sincerely thank my parents and especially my wifeVan Anh and son Nhan for their great support and patience during my study Ihope in the future I can return all their love

Bui Duc Vinh was born in Vinh Phuc, Vietnam, on the 7th April 1972 In October

1991 he started his studies in Civil Engineering at Ho Chi Minh University ofTechnology (HCMUT), where he received his Bachelor degree in 1996, specialize

in Coastal Engineering He started joint Faculty of Civil Engineering (FCE),HCMUT and worked as research assistant Two year after, 1998, he obtainedMaster Degree in Mechanic of Construction from University of Liege, Belgium

He continued his studies on structural engineering and focused on high strengthconcrete material, modelling of concrete structures

In Dec 2006, he jointed research team of Prof Dr.-Ing habil Nguyen Viet Tue,

at Institute for Structural Concrete and Building Materials, University of Leipzig(IMB, Uni-Leipzig) At here, his work concentrates on investigation structuralbehaviour of steel-concrete composite beams made of ultra high performanceconcrete March 2010 he finished his dissertation under the supervision of Prof.Nguyen Viet Tue

Ultra-High Performance Concretes (hereafter, UHPC) have high mechanical

strengths (f c > 150 MPa, f t > 7 MPa) and exhibit quasi-strain hardening in

tension Their very density improve durability and extend long service life Thesteel-concrete composite beams with concrete slab made of UHPC possess ad-vanced properties give significant improvement in ultimate strength of the com-posite beams The research reported in this thesis aimed to determine the perfor-mance and structural behaviour of composite steel-UHPC elements in bending

In addition, the continuous Perfobond based shear connectors that belong to thebeams was investigated as well

The Experimental assessment of the shear connector was conducted through 11series Push-Out test with 27 specimens In order to predict shear capacity, char-acteristic load-slip curves as well as contribution of constituents The connec-tors without any reinforcement show very poor ductility, the characteristic slipreached lower 1.5mm only They could be classified as non-ductile connector.The headed stud show better characteristic load-slip response, but this connec-tor often failed by shanked at the base of connector The shear connector withadded reinforcement in front cover and dowel exhibits better performance thanheaded stud connection in both terms of load capacity and ductility The testpointed out that embedded rebars in dowel play an important role in improve-ment performance of the connector The contribution of steel fiber less importantthan and It is not obviously when steel fiber vary in range of 0.5% to 1.0%.The structural response of the composite members under bending with the UHPCslab in compression was investigated with four points bending test of six full scalecomposite beams The concrete mix contained either 1% fibres or 0.5% (by vol-ume) of straight steel fibres with concrete strength of approximately 150 MPa.The experimental study demonstrates that the use of UHPC slab with contin-uous shear connector is possible, and it enhances the performance of compositeelements in terms of resistance and stiffness

The finite element analysis of the Push-Out specimens and composite beamswhich tested in this investigation was carried out using software ATENA Fullthree dimension models for both Push-Out specimens and composite beams weredeveloped in order to taken into account complexity of geometry The concrete

is not only provide ultimate strength, global behaviour but also explained localdamage area as well process of collapse occurred in structures However, the FEanalysis need more improvement in concrete material model, in order to used forparameter studies.

Finally, based on result of experimental and numerical investigation a numerousrecommendations are issued for practical design The results form this workprovide to better knowledge on using new UHPC in composite structures It alsocontribute to provision of design code

Foreword iii

1.1 State of the art 1

1.2 Context and motivation 3

1.3 Objectives of study 4

1.4 Scope of work 5

1.5 Structure of the thesis 6

2 Consideration aspects of steel-concrete composite beams 7 2.1 Introduction 7

2.2 Single span composite beams under sagging moment 9

2.2.1 Basic Structural Behaviour 9

2.2.2 Structural composite beam with continuous shear connection 12 2.3 Perfobond shear connector (PSC) 14

2.3.1 Conventional Perfobond shear connector 14

2.3.2 Modified pefobond shear connectors 18

2.4 Development of concrete technology 20

2.5 Composite beam made of UHPC 21

2.6 Finite Element modelling 22

2.6.1 modelling of composite beams 22

2.6.2 Modelling of Push-Out test 24

2.7 Design of composite beam 25

2.7.1 Limit state design philosophy 25

2.7.2 Methods for analysis and design 26

2.7.3 Resistant capacity of composite beam under sagging moment 26 2.7.4 Partial shear connection 28

2.7.5 Ductile and non-ductile shear connectors 28

2.8 Summary 29

3 Characterization material properties of UHPC 31 3.1 Development of UHPC-A Historical perspective 31

3.2 Constituent materials of Ultra High Performance Concrete 33

3.2.1 Principle of UHPC 33

3.2.2 Composition of UHPC 34

3.2.3 Cost of UHPC 36

3.2.4 Material used in this work 37

3.3 Relevant material properties 38

3.3.1 Properties of fresh UHPC 38

3.3.2 Time dependent properties of UHPC 39

3.3.3 Durability 40

3.4 Mechanical behaviour characterization 42

3.4.1 Development of compressive strength 42

3.4.2 Stress-strain behaviour in uni-axial compression 43

3.4.3 Bi-axial behaviour of UHPC 46

3.4.4 Flexural and direct tension behaviour of UHPC 48

3.4.5 Fracture properties of UHPC 49

3.5 Concluding remarks 51

4 Experimental study for perfobond shear connector in UHPC 53 4.1 Introduction 53

4.2 Experimental programs and specimens 54

4.2.1 Push-Out test specimens 54

4.2.2 Arrangement for Push-Out series 59

4.2.3 Standard Push-Out test setup 60

4.2.4 Loading procedure 62

4.3 Test results and observations 62

4.3.1 Resistance and slip results 62

4.3.2 Behaviour of headed stud shear connectors in UHPC 63

4.3.3 General behaviour of perfobond shear connector in UHPC 65 4.3.4 Influence of dowel profile and test setup 67

4.3.5 Influence of fiber content to load slip-behaviour 68

4.3.6 Influence of transverse reinforcement arrangement 71 4.3.7 Influence of embedding reinforcement through concrete dowel 72

4.4 Summary conclusions for Push-Out test 73

5 Experimental investigation on the structural behaviour of steel-UHPC composite beams 75 5.1 Introduction 75

5.2 Experimental program for composite beams 75

5.2.1 Aim and Objectives 75

5.2.2 Design and construction of test specimens 76

5.2.3 Test set-up and instrumentation 79

5.3 Analysis of the test results and observations 81

5.3.1 General 81

5.3.2 Structural behaviour and Observations of beam B1 and B2 83 5.3.3 Structural behaviour and Observation of beam B3 and B4 89 5.3.4 Test results and observing of beam B5 93

5.3.5 Test results and observing of beam B6 97

5.4 Shear flow distribution in composite beam 101

5.4.1 Load-slip behaviour in composite beam versus Push-Out test101 5.4.2 Distribution of longitudinal shear forces 103

5.5 Summary conclusions 104

6 Material models for Finite Element Modelling 107 6.1 General 107

6.2 Material models for structural steel and reinforcement 108

6.3 Microplane M4 material model for concrete 109

6.3.1 Aspects of concrete material model 109

6.3.2 Microplane M4 material model in ATENA 110

6.4 Parameter study of Microplane 115

6.4.1 Setting up virtual test 115

6.4.2 Input parameter and sensitivity analysis 117

6.4.3 UHPC experimental data 117

6.4.4 Results of M4 model parameters investigation and discussion118 6.5 Proposed set of parameter for UHPC 123

6.5.1 Adjustment strategy for model parameters 123

6.5.2 Result of compression and bending modelling with M4 123

6.6 Concluding remarks 124

7 Finite Element Modelling 127 7.1 Introduction 127

7.2 Modelling of Push Out Test 128

7.2.1 Finite element model 128

7.2.2 Experimental validation finite element model 132

7.2.3 Local behaviour Push-Out specimens 135

7.2.4 Proposed model for prediction ultimate capacity of perfor-bond shear connector 141

7.3 Modelling of composite beam 146

7.3.1 Finite element model 146

7.3.2 Validation of the FE model 149

7.3.3 Local stress distribution in steel girder and shear connectors 155 7.3.4 Shear flow on concrete dowel 157

7.4 Summary conclusion 157

8 Conclusions and Future Perspective 159 8.1 Conclusion 159

8.1.1 Ultra high performance concrete 159

8.1.2 Composite beam members made of UHPC under static load 160 8.1.3 Perfobond based shear connectors in UHPC 161

8.1.4 Modelling of composite beams 162

8.2 Recommendations for further research 162

A Appendices: Concrete mix proportional 165 A.1 List of tables for constituent materials 165

B Appendices: Standard Push-Out Test 169 B.1 Experimental results of Standard Push-Out test 169

B.2 List of drawings and charts 169

C Appendices: Bending test of composite beam 181 C.1 Design of steel-concrete composite beams for bending test 181

C.2 List of drawings and charts 181

FE Finite Element

FEA Finite Element Analysis

FEM Finite Element Methods

NFEA Nonlinear Finite Element Analysis

FES Finite Element Simulation

FEMD Finite Element Modelling

SG Strain gauge

LVDT Linear Variable Displacement Transducer

CMOD Crack Mount Opening Displacement

NSC Normal Strength Concrete

CSC Conventional Strength Concrete

HPC High performance Concrete

UHPC Ultra High Performance Concrete

UHPFRC Ultra High Performance Fiber Reinforced ConcreteRPC Reactive Powder Concrete

SCCB Steel Concrete Composite Beam

UHPCSCCB Steel Concrete Composite Beam Made of UHPCSHC Shear Connector

SPOT Standard Push-Out Test

HSSC Headed Stud Shear Connector

PFSC Perfobon Shear Connector

CDW Closed dowel

M4 Bazant’s Miroplane material model for concrete

RILEM International Union of Laboratoies and Experts

in Construction Materials, System and Structures

Greek characters

σ c stress of concrete

δ uk characteristic value of slip capacity

η degree of shear connection

φ diameter of concrete dowel

Latin lower case letters

b o bottom width of shear surface in dowel area

d depth of shearing cone

n dw numer of dowel in the Push-Out specimen

h sc height of steel rib

t sc thickness of steel rib

q u shear capacity per perfobond

P dw shearing capacity of plain concrete dowel

P r contribution of rebar in dowel to capacity of PSC

P fr contribution of rebar in front cover to capacity of PSC

P a contribution of steel rib to capacity of PSC

Latin upper case letters

A Cross-sectional area of the effective composite section

neglecting concrete in tension

A a cross-sectional area of the structural steel section

A b cross-sectional area of bottom transverse reinforcement

A bh cross-sectional area of bottom transverse reinforcement in a

haunch

A c cross-sectional area of concrete

A cc cross-sectional area of concrete shear per connector

A r area of embedded reinforcement in concrete dowel

A rf amount area of reinforcement in front cover

L e span of composite beam

M Bending moment

D uiameter of concrete dowel

P u ultimate resistance of Push-Out specimen

P Rk ,1 characteristic value of the shear resistance of a single connector

P Rk characteristic value of the shear resistance of Push-Out specimen

Mechanical Properties

f c Cylinder compressive strength

f ck Characteristic value of the cylinder compressive strength of

concrete

f ct Tensile strength of concrete

f c ,28d compressive strength of concrete at 28 days

f y Nominal value of the yield strength of structural steel

f y ,r yield strength of reinforcement

E c elastic modulus of concrete

E a elastic modulus of structural steel

E a ,r elastic modulus of reinforcement

1.1 Karl-Heine footbridge in Leipzig-Germany: concrete filled steel tube structures, after Koenig [56] (left), and the composite floor

of a residential building in London[26] (right) 1

1.2 Basic mechanism of composite action 2

1.3 Perfobond shear connection in composite beam 4

2.1 Typical cross sections of composite beams [26] 7

2.2 Typical shear connectors, after Oehlers and Bradford [68] 8

2.3 Stages of composite beam at different load levers[26] 10

2.4 Longitudinal shear force on connectors[26] 10

2.5 Typified VFT-WIB composite section (above) and application in Vigaun bridge project, after Schmitt et al [94] 14

2.6 Push-Out specimens and test setup, a) general specimen (Oguejiofor and Hosain [83]), b) specimen with profile steel sheet (Kim et al [55]) 16

2.7 Shear transfer mechanism from concrete slab to steel rib 17

2.8 Various kind of Perfobond Shear connector in composite beam 18

2.9 Push-Out test of the VFT-WIB connector [93] 19

2.10 Discrete and continuous model for shear connector in composite beams 23

2.11 Elasto-Fracture-Plastic based material models for steel and concrete in Finite element modelling of Push-Out test and com-posite beam 23

2.12 Push-Out specimen model of Kraus and Wurzer [57] 25

2.13 Ideallized tress-strain diagrams used in the plastic method, [26, 27] 26 2.14 Plastic analysis of composite section under sagging moment, 1a-neutral axis in concrete slab; 1b-1a-neutral axis at the bottom of com-posite slab; 2a-neutral axis lies within top flange of steel section; 2b- neutral axis in the web 27

2.15 Design method for partial shear connection [47, 48] 27

3.1 Historical development of UHPC 32

3.2 Comonents of a typical UHPC 34 3.3 Relative density vesus w/c ratio, after Richard and Cheyrezy [90] 36

3.4 Estimation cost of constituent materials for UHPC, (a):UHPCwithout steel fiber, (b) with 1% steel fiber [58] 373.5 Autogeneous shrinkage of UHPC with and without coarse aggre-gates, after Ma et al [69, 70] 393.6 Creep of UHPC with and without coarse aggregates, after Ma andOrgrass[71, 73] 393.7 Porosity of UHPC with and without heat treated, after Cwirzen [23] 413.8 Comparison durability properties of NSC, UHP and UHPC AfterSuleiman et al.[99] 413.9 Development compressive strength, after Ma [74] 423.10 Test setup for stress-strain response under uni-axial compression 443.11 Loading procedure for uni-axial compression test 443.12 A comparison of stress-stress curves of NSC, HPC and UHPC(left),and Poinsson’s ratio (right) After (Tue et al.) [101] 443.13 Relation elastic modulus vesus compressive strength.(Tue et

al.[101, 70]) 453.14 Comparison influence of grain size and fiber content to bi-axialstrength increment, modified from Curbach and Hampel [22] 473.15 Proposal reduction strength under compression-tension load, mod-ified from (Fehling et al [29]) 473.16 Flexural tensile stress-deflection diagram of G7-UHPC, by Tue

et al.[108] 483.17 Notched beam three points bending test(left) and Wedge splittingtest (right) to determine fracture energy of concrete 493.18 Characteristic length versus versus compressive strength [32] 504.1 Behaviour of headed stud shear connector in NSC, after John-son [47] 534.2 Standard Push-Off Test, Setup 1 (a) and Setup 1 (b) 554.3 Typical stress-strain curve of structural steel at room temperature,modified Outinen et al [85] 564.4 Typical stress-strain curves of Bst500 reinforcement 564.5 Material responses of G7-UHPC 1% steel fiber, stress-strain di-agram in compression test (left) and stress-deflection in RILEMbeam test(right) 584.6 Casting Push-Out specimens 584.7 CDW (above line) and ODW (below line) shear connectors, (a &e)-without rebar, (b & f)-rebar in dowel, (c & g)-rebar in frontcover, (d & h)-rebar in dowel and front cover 604.8 Push-Out specimen in 4000 kN load frame and controller system 614.9 Instrumentation setup in SPOT Setup 1(left) and Setup 2 (right) 61

4.10 Load history for SPOT 62

4.11 Load-slip diagram of headed studs shear connectors in UHPC 64

4.12 Crack opening in concrete surfaces 64

4.13 Failure process and shanked of HSSH at footing 65

4.14 Basic mechanics of perfobond shear connector (left), stress state in concrete dowel, after Kraus and Wurzer [57](right) 66

4.15 Deformation of the steel ribs after test 66

4.16 Overview behaviour of perfobond shear contectors 66

4.17 Load-Slip behaviour of CDW and ODW (1 % steel fiber) 68

4.18 Influence of fiber content on load-slip behaviour series 8: 0.5% and series 9: 1% vol steel fiber 69

4.19 Crack opening curves of series 8 and 9 69

4.20 Crack pattern of SPOT with UHPC 0.5% (left) and 1% (right) steel fiber 70

4.21 Crack on the concrete surface, without reinforcement in cover (left) and with reinforcement(right) 70

4.22 Effect of transverse reinforcement arrangement on load-slip be-haviour 71

4.23 Influence of reinforcement thought dowel 72

5.1 Sketch layout of Beam B1 and B2 77

5.2 Sketch layout of Beam B3 and B4 77

5.3 Design layout of Beam B5 and B6 78

5.4 Instrumentation for flexural test of composite beams Series 1 80

5.5 Instrumentation for flexural test of composite beams Series 2 80

5.6 Equipment for flexural test of composite beams Series 1-2 81

5.7 Force-deflection curve before and after remove residual strain 82

5.8 Load-deflection behaviour of composite beam B1 and B2 83

5.9 Plastic of steel girder and crushed of concrete slab 83

5.10 Moment curvature relationship of beam B1 and B2 85

5.11 Strain development in concrete slab (left) and steel girder(right) of composite beam B1 and B2 86

5.12 Strain development in cross section of composite beam B1 and B2 86 5.13 Longitudinal slip of beam B1 (left) and B2 (right) 87

5.14 Lateral strain surround hole of perforated strip 88

5.15 Load-deflection behaviour of composite beam B3 and B4 89

5.16 Failure of beam B3 due to collapse of shear connector in right side 90 5.17 Load-strain behaviour of composite beam B3 and B4, concrete slab (left) and steel girder (right) 92

5.18 Load-strain development in cross section beam B3(left) and B4 (right) 92

5.19 Diagram Load-longitudinal slip in beam B3 and B4 935.20 Load - deflection behaviour diagrams of beam B5 945.21 Load - strain response of beam B5 955.22 Longitudinal slip of beam B5 955.23 Slip development of beam B5 965.24 Load - deflection diagrams of beam B6, UHPC G7 0.5 % fibercontent 975.25 Load - slip behaviour of beam B6 985.26 Failure progress of composite beam B6 995.27 Load-Strain at middle span section of beam B6 1005.28 Strain development in middle span section (left) and one thirdsection (right) of beam B6 1005.29 Stress-strain over slab thickness 1015.30 Comparison load slip behaviour of shear connector in compositebeam and push out test 1025.31 Comparison load slip behaviour of shear connector in compositebeam and push out test 1025.32 Slip distribution versus degree shear connection 1035.33 Longitudinal shear force in composite beams 1036.1 Bilinear Elasto-plastic material model for structural steel 1086.2 Calculation macro stress scheme in microplane model 1116.3 Strain component on a micro plane 1116.4 Microplane boundary 1136.5 FE simulation RILEM (left) bending test and uni-axial compres-sion (right) 1166.6 Typical stress-strain of uni-axial compression test (left) and bend-ing stress-displacement diagram of RILEM three points bendingtest (right) 1166.7 Effect of changing elastic modulus to flexural and compressionspecimens 119

6.16 Stress-displacement and Stress-strain response of B4Q-UHPC (1%vol steel fiber) with Microplane M4 1247.1 Geometry of push-out test specimens 1287.2 Finite Element model of Push-Out specimen 1297.3 Loading, boundary conditions and constrain DOFs at contact sur-faces between steel and concrete 1317.4 Comparison load-slip response of experimental and FE analysis forPush-Out series 3 and 4 (open dowel) 1347.5 Comparison load-slip response of experimental and FE analysis forPush-Out series 6 and 7 (closed dowel) 1347.6 Local deformation of the series 4 - Open dowel with test setup 2 1367.7 Local deformation of the series 7 - Closed dowel with test setup 1 1367.8 Local stress distrubution in the steel rib 1377.9 Local strain distribution in concrete block 1387.10 Stress concentration distribution in rebars of Series 4 (ODW) and

7 (CDW) 1407.11 Simplified shearing cone assumption 1407.12 Geometry of composite beam for FE modelling 1467.13 Finite Element mesh of a composite beam model 1477.14 Interface between steel and concrete surface 1477.15 Deformed shape of the beam B1 and FE simulation 1507.16 Comparison test and modelling results of beam B1 and B2, force

- deflection 1517.17 Comparison test and modelling results of beam B3 and B4, force

- deflection 1517.18 Comparison test and modelling results of beam B1, force-strain 1527.19 Comparison test and modelling results of beam B2, force-strain 1527.20 Comparison test and modelling results of beam B3, force-strain 1537.21 Comparison test and modelling results of beam B4, force-strain 1537.22 Comparison local slip of beam B1 (left) and B2 (right) 1547.23 Stress distribution in girder, beam B1 to B4 1557.24 Stress distribution in steel rib 1567.25 Longgitudinal stress in steel rib of shear connector, beam B1 andB2 156B.1 Push-Out test setup S1 and S2 170B.2 Rebars arrangement of Push-Out specimens 171B.3 Push-Out test reults: Load-Slip and Crack opening, Series1-Headed stud shear connector, specimen-1(a), specimen-2(b),specimen-3(c) 172

B.4 Push-Out test reults: Load-Slip, Series 2-ODW without rebar(left), Series 3-ODW with rebar in core(right) 173B.5 Push-Out test reults: Load-Slip and Crack opening, Series 4-Opendowel with rebar in core and front cover, specimen-1(a), specimen-2(b), specimen-3(c) 174B.6 Push-Out test reults: Load-Slip and Crack opening, Series 5-CDWwithout Reinforcement, specimen-1(a), specimen-2(b), specimen-3(c) 175B.7 Push-Out test reults: Load-Slip and Crack opening, Series 6-CDWwith rebar in core, specimen-1(a), specimen-2(b), specimen-3(c) 176B.8 Push-Out test reults: Load-Slip and Crack opening, Series 7-Opendowel with rebar in core and front cover, specimen-1(a), specimen-2(b), specimen-3(c) 177B.9 Push-Out test reults: Load-Slip and Crack opening, Series 8-CDW with rebar in cover-UHPC 0.5% steel fiber, specimen-1(a),specimen-2(b) 178B.10.Push-Out test reults: Load-Slip and Crack opening, Series 9-CDW with rebar in cover-UHPC 1.0% steel fiber, specimen-1(a),specimen-2(b) 179B.11.Push-Out test reults: Load-Slip and Crack opening, Series 10-11-CDW with rebar in core and front cover-UHPC 1.0% steel fiber,

φ8mm-(a), φ12mm-(b) 180

C.1 Design of the composite beam B1 182C.2 Design of the composite beam B2 183C.3 Design of the composite beam B3 184C.4 Design of the composite beam B4 185C.5 Design of the composite beam B5 186C.6 Design of the composite beam B6 187C.7 Experimental setup of the composite beam B1 188C.8 Experimental setup of the composite beam B2 189C.9 Experimental setup of the composite beam B3 190C.10.Experimental setup of the composite beam B4 191C.11.Experimental setup of the composite beam B5 and B6 192C.12.Beam B1, Load-deflection and Load-rotation (a), strain in girdersection 1-1 (b) and strain in girder section 2-2 (c) 193C.13.Beam B1, Load-strain in concrete slab (a), strain in steel rib (b)and slip (c) 194C.14.Beam B2, Load-deflection and Load-rotation (a), strain in girdersection 1-1 (b) and strain in girder section 2-2 (c) 195

C.15.Beam B2, Load-strain in concrete slab (a), strain in steel rib (b)and slip (c) 196C.16.Beam B3, Load-deflection and Load-rotation (a), strain in girdersection 1-1 (b) and strain in girder section 2-2 (c) 197C.17.Beam B3, Load-strain in concrete slab (a), strain in steel rib (b)and slip (c) 198C.18.Beam B4, Load-deflection and Load-rotation (a), strain in girdersection 1-1 (b) and strain in girder section 2-2 (c) 199C.19.Beam B4, Load-strain in concrete slab (a), strain in steel rib (b)and slip (c) 200C.20.Beam B5, Load-deflection (left), strain in girder and concrete slab

at section 1-1 (right) 201C.21.Beam B6, Load-deflection and Load-rotation (a), strain in girderand concrete slab section 1-1 (b) 201C.22.Beam B6, strain in girder and concrete slab section 2-2 (a), Load-longitudinal slip along left and right side of the beam (b) 202D.1 Structure of the program 203D.2 Flow chart of calibration model parameter of microplane M4 204D.3 Main screen of the program 205D.4 Result extraction 205D.5 Quick plot experiment results 206D.6 Atena datafile editor 206

3.1 Diameter range of granular class for UHPC, after Richard andCheyrezy[90] 343.2 Mixture proportion of UHPC 383.3 title of table 413.4 Fracture parameters of UHPC for different mix designs, after

Ma[74] 503.5 Tensile fracture properties of UHPC with steel fiber, modifiedFehling et al.[32] 524.1 Mechanical properties of steel grade S355 and reinforcing bar Bst

500 574.2 Material properties of UHPC 574.3 Parameter for Push-Out test program 594.4 Summary Standard Push-Out Test results 635.1 Description of composite beams 765.2 Transverse reinforcement arrangement in concrete slab 765.3 Summary of test result of the composite beams 825.4 Comparison of ultimate strength, deflection and stiffness of beamsB2 with B3 and B4 905.5 Peak slip location versus actual shear connection degree 1036.1 Boundaries for the microplane model parameters 1176.2 Value of M4 model parameters for UHPC G7 and B4Q 1247.1 Comparison of ultimate capacity predicted by ATENA with ex-perimental values 1337.2 Push-Out test and modelling data for linear regression analysis 1437.3 Push-Out test and modelling data for linear regression analysis(con’t) 1447.4 Verification prediction model with experimental and simulation data1457.5 Description of composite beams for experimental and modelling 1507.6 Ultimate load and deflection results for the experimental and nu-merical analyses 151

1.1 State of the art

The term Composite Construction is normally understood within the context

of buildings and other civil engineering structures, to imply the use of Steel andConcrete combine together as a unified component The aim is to archive a higherlevel of performance than would be have been the case had the two materialsfunctioned separately Steel and concrete can be used in mixed structural sys-tems, for example concrete cores encircled by steel tubes, concrete slab ”glued”’with steel girder via shear connection in order to form composite beam whichmost widely used in practical construction Moreover, composite columns offermany advantages over bare steel or reinforced columns, particularly in reducingcolumn cross-sectional area Another important consideration is fire resistance.Figure 1.1 shows Karl-Heine pedestrian bridge in Leipzig (Koenig [56]), and thecomposite floor of a residential building in London [26] They are the typicalillustration of using hybrid structures in construction

Figure 1.1.: Karl-Heine footbridge in Leipzig-Germany: concrete filled steel tube structures,

after Koenig [56] (left), and the composite floor of a residential building in London[26] (right)

The basic mechanics of composite action is best illustrated by analysis a posite beam under bending load which demonstrated in Fig 1.2 In the case

com-of non-composite (a), the concrete slab is not connected to the steel section and

therefore behaves independently As it is generally very weak in longitudinalbending it deforms to the curvature of the steel section and has its own neutralaxis The bottom surface of the concrete slab is free to slide over the top flange

of the steel section and considerable slip occurs between the two The bendingresistance of the slab is often so small that it is ignored

Alternatively, if the concrete slab is connected to the steel section (b), both acttogether in carrying the service load Slip between the slab and steel section

is now prevented and the connection resists a longitudinal shear force quently, the load bearing capacity of the second beam (b) is few times greaterthan the first beam (a)

Figure 1.2.: Basic mechanism of composite action

The characteristic of the steel-concrete composite is exhibited by resistance ofeach contributed material portion and the resistance of shear connection Whenthe connection cannot resist all of the forces applied then considered as partialconnection, otherwise full shear connection

Most frequently, composite beam is designed to carry bending load Regardingthe stress and strain distribution of composite section as shown in Fig 1.2b,

the neutral axis dose not often fall at the interface Good design will attemptlocate this axis close to this position Thus whole concrete slab is subjected tocompressive force, whereas steel girder to be concerned tension force In prac-tical constructions, the composite beam is often made of either normal strengthconcrete (in short NSC) or high strength concrete (in short HSC) for slab andhigh strength steel for girder.

1.2 Context and motivation

Recent development of concrete technology resulting a new type of concrete withmany advanced properties, it is called in common name Ultra High PerformanceConcrete (in short UHPC) The key benefits of UHPC are considered in applica-tion point of view as follows:

very high in compressive strength and tensile strength which are ideal tocarry compression load in the composite beams

addition steel fiber will enhanced ductility behaviour

reduce total weight of structural member

with high flow ability properties, concrete can be complete fulled for plex geometry members

com-extraordinary durability compare to conventional concrete, reduce maintaincost during service time

most disadvantage of UHPC is highly cost at the moment, it may be creasing in the near future when increasing amount of applications Thedetail characteristic of UHPC will be mentioned in the chapter 3

de-In the structural member behaviour outlook, with NSC the resistance of concreteslab is often less than steel girder, the neutral line lie in the web

By substituting UHPC to NSC/HSC, the resistance of concrete materials could

be reached resistance capacity of steel easily Consequently obtaining optimalload caring of each contribute material The replacement is not only increasethe stiffness and overall ultimate strength but also reduce cross section of thecomposite beams

Fig 1.3 illustrates the idea using perforated steel rib as continuous shear tion in the composite beam This type of shear connector was first introduced byLeonhardt[62] Perforation strip are welded on top flange of steel girder or cut

connec-directly from web At construction phase, UHPC will be flowed through rated hole the dowels formed Under loading, interaction is developed by concreteengaging with perforations strip, the working mechanism of shear connector can

perfo-be illustrated similar to the action of a dowel In principle, this method brings

to many advantages in practical construction, while load transfer performance isstill guaranteed

Figure 1.3.: Perfobond shear connection in composite beam

It is well known that, at interaction area between perforated strip and UHPCdowel, the behaviour is combination of tension-shear and compression TheUHPC with very high compressive strength but less ductility must be treated

to satisfy characteristic ductility requirement of shear connector in compositebeam The application of this device for shear connection incorporating steelgirder still requires further verification

Due to the high cost of UHPC material and testing, the experimental study

is unable to cover all range of interested problems Consequently, numericalsimulation play an important role in this works However, the behaviour ofUHPC is different with conventional concrete, therefore suitable material model

is required to illustrate mechanism of beam as well concerned problems

1.3 Objectives of study

The present study aims to investigate performance and structural behaviour ofsteel-concrete composite beam made of UHPC under bending, and it also provide

a better knowledge of perfobond shear connector response in Push-Out test andconjugate with steel girder More precisely, the following points are explored:Characteristic of UHPC would be better known and understood, especiallyfocus on basic mechanical properties.

A better knowledge on response of the perfobond shear connectors inUHPC, appropriate choice of shear connector for UHPC composite memberwould be achieved

Experimental investigation of UHPC composite beam subjected flexuralload, which provides structural behaviour of member under serviceabilityand ultimate limit state, in order to answer the following questions:

- Is it possible to build composite ”UHPC-Steel” elements with monolithicbehaviour; and how can the advantageous UHPC properties be exploited in suchcomposite elements?

- What do resistance and failure modes of ”UHPC-Steel” elements would beshown under bending?

- How do local deformations, stresses and cracking evolve in the compositemembers under monotonic load?

Nonlinear finite element models must be evaluated and developed in order

to predict the structural behaviour of shear connectors and ”UHPC-Steel”composite beams The simulation should be explored following aspects:

- Are existing material models appropriate to simulate behaviour of UHPC?

- How to construct suitable structural models for shear connector and posite beams?

com What do local behaviour would be shown?

- How to improve performance of the ”UHPC-Steel” composite beam?

On the basis of the results, a design model and guidelines are developed forpractical application of UHPC composite members

1.4 Scope of work

This work is part of priority research program SPP 1182: ”Sustainable Building

with Ultra High Performance Concrete”, which collaborate by numerous of

uni-versities in Germany The concrete material and design of composite were priorplanned, and oriented to the trend of this project The flexural behaviour of sin-gle span composite beams were limited to sagging moment only The continuous

beam with hogging moment (negative moment) at support is not considered inthis work.

1.5 Structure of the thesis

The thesis consists of eight chapters Chapter one is the outline introduction

to innovation context of development of UHPC and its application into hybridsteel-concrete structures The main aspect and objective of this research workwas also mentioned

Chapter two presents relevant literature review of the behaviour of steel-concretecomposite beams made of UHPC The content includes material properties as-pect, load transfer mechanism in the beam, as well as experiment and modelling

of composite beams

In Chapter three, the state of the art of UHPC are brief introduced, properties

of UHPC are characterized and main properties which influence on behaviour ofstructures under loading service are to be discussed in details

Chapters four and five present an experimental program to investigate the haviour of shear connectors and composite beams The structural tests are con-ducted on standard Push-Out test (SPOT) specimens according to guideline ofEuro Code 4 (EC4), the beams are performed on large scale Experimental frame-work is divided into two phases namely Push-Out test of shear connectors, thenbending test for composite beam The discussion and analysis of the experimentalresults are presented

be-The first part of chapters six presents briefly material the model for structuralsteel and reinforcement was well Principally, this chapter focuses on the Mi-croplane M4 material model for concrete Based on parameter investigation, aset of model parameters for UHPC was introduced

Chapter seven describe a development of three dimension model for simulation ofPush-Out specimens and composite beams The parameter study was carried outfor various type of shear connectors (SHC) and steel-concrete composite beams(SCCB) Discussion on modeling results and conclusion were drawn

The last chapter of this dissertation presents final conclusion based on this search project and provide future prospective concerning to SCCB and hybridstructures made of UHPC

re-2.1 Introduction

The most important and most frequently encountered combination of tion materials is that of steel and concrete, with applications in multi-storeybuildings and constructions, as well as in bridges These materials can be used

construc-in mixed structural systems, for example concrete slab glued with steel girder, aswell as in composite structures where members consisting of steel and concreteact together Steel and concrete have the same expansion coefficient, and eachmaterials is strong in either compression or tension Concrete also provides cor-rosion protection and thermal insulation to the steel at elevated temperaturesand additionally can restrain slender steel sections from local or lateral-torsionalbuckling These essentially different materials are completely compatible andcomplementary to each other

Composite beams, subjected mainly to bending, consist of a steel section actingcompositely with one (or two) flanges of reinforced concrete The two materialsare interconnected by means of mechanical shear connectors For single spanbeams, sagging bending moments, due to applied vertical loads, cause tensileforces in the steel section and compression in the concrete deck thereby allowingoptimum use of each material Fig 2.1 and Fig.2.2 show several compositebeam cross-sections and shear connectors respectively, which are widely used inpractical construction

Figure 2.1.: Typical cross sections of composite beams [26]

Figure 2.2.: Typical shear connectors, after Oehlers and Bradford [68]

The shear connectors in composite beams are used to develop the compositeaction between steel girder and concrete They are provided mainly to resistlongitudinal shear force, therefore must meet a various requirements, such as[26]:

transfer direct shear at their base

create a tensile link into the concrete

economic to manufacture and welding

The most common type of mechanical shear connector is the headed stud shown

in Fig 2.2a It can be welded to the upper flange either directly in the factory

or through thin galvanised steel sheeting on site The Behaviour and ultimatestrength of connectors can be examined by Push-Out test according to availablestandards such as EuroCode4 [27] For the design of headed stud, the fol-lowing aspects are considered; shear strength of stud shank, bearing strength ofconcrete, additional contribution of chemical bonding and friction In spite of itswide application, the headed stud has many deficiencies such as a slip Behaviourbetween stud and concrete, and fatigue failure at welding zone [26, 80, 47, 55]Recently, a very high strength cement based composite called Ultra High Perfor-mance Concrete (UHPC) has been developed It provides many enhancements

in properties compared to conventional and high strength concrete (HSC) In

the composite beams, the replacement of normal strength concrete (NSC) withUHPC lead to an improvement in the load carrying in the compression zone.Generally, a significant increase in load bearing capacity and stiffness of thebeam is achieved, resulting in saving dead load, reducing construction depth aswell as construction time However, as reported in Johnson [47], Hegger etal., Tue et al [105] the headed stud shear connector is not appropriate inthe HSC/UHPC slab due to restrict deformation surrounding stud area Thecombination of perfobond shear connector in UHPC will be optimized in bothterm of material and structural system.

This chapter aims to review researches relevant to the Behaviour of compositebeams under bending load, which focuses to composite beam/slab with perfobondshear connector Different aspects of the problem are discussed such as the basicBehaviour of composite beams, innovation of concrete technology, mechanicalshear connection The numerical modelling of the structural composite beamsand the currently available design procedures will be also mentioned

2.2 Single span composite beams under sagging moment

2.2.1 Basic Structural Behaviour

The way in which a composite beam behaves under the action of low load, mediumand the final failure load can be briefly described in stages as follows [26]:

It can be seen from the strain diagram that, if the slab is thick enough thenthe neutral axis lies within the concrete As a result some of the concrete is intension If the slab was thin, it is possible that the neutral axis would be in thesteel and then the area of steel above the axis would be in compression Thisstage corresponds to the service load situation in the sagging moment region ofmost practical composite beams

In this stage applied load was increased, thus caused rise to deformation in the

shear connection This deformation is known as slip and contributes to the overall

deformation of the beam Fig 2.3b shows the influence of slip on the strainand stress distribution This stage corresponds to the service load stage thatcomposite beams class has been designed as partially shear connection However,for many composite beams slip is very small and may be neglected.

Stage 3

The steel girder achieves yield limit strain first, plasticity develops and then most part of steel section becomes plastic It occurs as similar fashion in concreteslab Stress block of whole section changes from triangular to shape shown inFig 2.3c that is very difficult to express in mathematical form In ultimate limitstate (ULS) it is assumed to be a rectangular block

al-If longitudinal shear resistance is big enough the slip can be neglected Thestrain in concrete slab could lead to over stress, then it is potentially possiblethat explosive brittle failure of the slab would occur However, in most practicalcase this situation could ever arise due to the deformation of shear connectors.The response of shear connector in load stage is illustrated as follows:

As the load increases the shear strain, the longitudinal shear force between theconcrete slab and steel girder increases in proportion For single span compositebeam under uniformly load, it is assumed to deform in an elastic manner andthe longitudinal shear force between slab and steel section can be expressed as

T = VS /I [96] Hence longitudinal shear force is directly proportional to the

vertical shear force, thus the force on the end connectors is the greatest Forlow loads the force acting on a connector produces elastic deformation The slipbetween the slab and the steel section will be greatest at the end of the beam.The longitudinal shear and deformation of a typical composite beam, at this stage

of loading, are shown in Fig 2.4a

If the load is further increased the longitudinal shear force increases too, and theload on the end stud may cause plastic deformation The ductility of the connec-tors means that the connectors are able to deform plastically whilst maintainingresistance to longitudinal shear force Fig 2.4b shows the situation when the endconnectors are deforming plastically By increasing applied load, the connectorsnear to the midspan section also begin sequentially to deform plastically Failureoccurs when once all of the connectors have reached their ultimate resistance asshown in Fig 2.4c The failure pattern is dependent upon the plastic defor-mation of shear connector As exhibited, the end connector must be consideredbefore other one close to the midspan area reaches its ultimate capacity Therequirement for ductility of shear connector is necessary

It can be seen that the failure of the composite beam is dictated by the tance of its three main components: steel girder, concrete slab as well as shearconnector the interaction of these components is very complex, in design thestress-strain relation of these materials are usually assumed as elastic- perfectplasticity [27].

resis-2.2.2 Structural composite beam with continuous shear connection

Steel-concrete composite beam with perforbond shear connectors have been rarelyinvestigated Jurkiewiez and Hottier [50, 51] studied Behaviour of simplesupport composite beams whose steel beam is an Tee girde without upper flange.Horizontal shear connection was designed as dovetail-shape (a variant of per-fobond) and cut directly on the web of I steel section By taking symmetriccharacteristic of shear connector, two steel beams obtained with only a cuttingline To improve the shear capacity and ductility, concrete dowel and horizontalwas combined acting together to resist longitudinal shear force Normal strengthconcrete with compressive strength of 48 MPa at 28 days was used for slab Nu-merous large scale specimens were constructed, three points bending tests wereconducted under static and fatigue load

Experimental results shows global Behaviour of the beam with novel shear nector is similar to that with usual connectors The response includes elasticity,yielding and plasticity domains as well A flexural failure occurred with a plastichinge in the mid-span cross section accompanied by yielding of the steel girderand crushing of the concrete The shear connectors did not fail during the testand allowed to efficiently transmit shear forces from the slab to the girder Thenew proposed shear connector is satisfactory in the bending Behaviour in accor-dance with requirements of design codes

con-In different context, Kim and Jeong [53, 46, 54] carried out experimentalinvestigations on the ultimate strength of steel-concrete composite bridge deckwith profiled steel sheeting and perfobond rib shear connectors In fact, compositeaction of one way bridge deck behaves similar to composite beam in flexuralmode The perforate steel rib with holes of 50mm diameter was welded directlyinto steel sheet and form continuous shear connectors The parameters such assteel deck profile, perfobond rid, reinforcement as well as concrete strength wereconsidered The Push-Out with the same shear connection of the deck was carriedout to determine the capacity of shear connector

The proposed deck system outperforms a typical cast in place (CIP) reinforceconcrete deck in several ways: its ultimate load-carrying capacity is approxi-mately 2.5 times greater; its initial concrete cracking load is 7.1 times greater;