development of steel-glass structures-rtssd

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Development of innovativesteel-glass structures in

respect to structural andarchitectural design

(Innoglast)

Research and

Innovation EUR 25316 EN


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EUROPEAN COMMISSION

Directorate-General for Research and Innovation

Directorate G — Industrial Technologies

Unit G.5 — Research Fund for Coal and Steel

E-mail: [email protected]

[email protected]

Contact: RFCS Publications

European Commission

B-1049 Brussels


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European Commission

Research Fund for Coal and SteelDevelopment of innovative steel-glassstructures in respect to structural and

architectural design(Innoglast)

B. AbelnInstitute of Steel Structures, RWTH Aachen University

Mies-van-der-Rohe-Str. 1, 52074 Aachen, GERMANY

E. PreckwinkelInstitute of Steel Construction,Dortmund University of Technology

August-Schmidt-Straße 6, 44221 Dortmund, GERMANY

E. Yandzio, M. Heywood

The Steel Construction InstituteSilwood, Ascot, SL5 7QN, UNITED KINGDOM

M. Eliášová, M. NetušilDepartment of Steel and Timber Structures,Faculty of Civil Engineering,

Czech Technical University in Prague

Thákurova 7, 166 29Praha 6, CZECH REPUBLIC

C. GrenierCentre Scientifique et Technique du Bâtiment

84 Avenue Jean Jaurès, Champs sur Marne, 77447 Marne la Vallée Cedex 2, FRANCE

Grant Agreement RFSR-CT-2007-000361 July 2007 to 31 December 2010

Final report

Directorate-General for Research and Innovation

2013 EUR 25316 EN


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LEGAL NOTICE

Neither the European Commission nor any person acting on behalf of the Commission isresponsible for the use which might be made of the following information.

The views expressed in this publication are the sole responsibility of the authors and do notnecessarily reflect the views of the European Commission.

More information on the European Union is available on the Internet (http://europa.eu).

Cataloguing data can be found at the end of this publication.

Luxembourg: Publications Office of the European Union, 2013

ISBN 978-92-79-24827-6doi:10.2777/91697

© European Union, 2013Reproduction is authorised provided the source is acknowledged.

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TABLE OF CONTENTS

Table of contents .....................................................................................................................................3

Final Summary .......................................................................................................................................7

Scientific and technical description of the results.............................................................................. 15

Objectives of the project .................................................................................................................... 15 Comparison of initially planned activities and work accomplished................................................... 17 Description of activities and discussions ........................................................................................... 19

1 Joining details and small scale tests ........................................................................................... 23

1.1 Selection of adhesives ...........................................................................................................23 1.2 Investigation of different connection types ...........................................................................24 1.3 Small scale tests (push-out tests) .......................................................................................... 25

1.3.1 Manufacturing of the specimen ....................................................................................26 1.3.2 Push-Out tension tests ..................................................................................................26 1.3.3 Results from tension tests ............................................................................................. 27 1.3.4 Push-Out shear tests ..................................................................................................... 29 1.3.5 Results from tension tests ............................................................................................. 29 1.3.6 Comparison of push-out tests with standardized tests .................................................. 30

1.4 Numerical analysis ................................................................................................................33

1.4.1 Material laws and push-out tests ..................................................................................33 1.4.2 Additional small scale tests ..........................................................................................34

1.5 Optimising and Design Rules ...............................................................................................37

2 Product application .....................................................................................................................39

2.1 Dimensions ...........................................................................................................................39 2.2 Application of hybrid beams .................................................................................................40 2.3 Connection details .................................................................................................................41

3 Development and verification of analytical models .................................................................. 43

3.1 Hybrid steel-glass-beams ...................................................................................................... 43

3.1.1 Hybrid beam with glass web made of one glass pane .................................................. 43 3.1.2 Hybrid beam with glass web made of several glass panes ........................................... 47

3.2 Steel-supported glass façades ................................................................................................ 49

3.2.1 Introduction .................................................................................................................. 49 3.2.2 Steel supported glass façade .........................................................................................49 3.2.3 Analytical model ..........................................................................................................50

3.2.3.1 Analysis techniques .................................................................................................52 3.2.3.2 Potential savings in building steel bracing ...............................................................55

4 Development of hybrid steel-glass-beams ..................................................................................57

4.1 Load carrying capacity and full-scale physical tests .............................................................57

4.1.1 Test set up..................................................................................................................... 57 4.1.2 Measurements ............................................................................................................... 57 4.1.3 Test specimen ...............................................................................................................57 4.1.4 Test results of short-time tests and analytical and numerical evaluation .....................58 4.1.5 Test results of long time tests and evaluation ...............................................................63

4.1.5.1 Small scale creeping tests ........................................................................................63 4.1.5.2 Full-scale creeping tests ........................................................................................... 63

4.2 Full-scale tests on stability problems ....................................................................................64

4.2.1 Test setup......................................................................................................................64


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4.2.2 Test matrix and dimensions of specimen .....................................................................65 4.2.3 Measurement ................................................................................................................ 66 4.2.4 Flexural buckling test results ........................................................................................67 4.2.5 Lateral torsional buckling test results ........................................................................... 68

4.3 Numerical studies .................................................................................................................. 69 4.4 Robustness ............................................................................................................................ 72

5 Development of steel-supported glass-systems ..........................................................................75

5.1 Small scale connection tests of the steel supported glass facades ......................................... 75

5.1.1 Introduction ..................................................................................................................75 5.1.2 Outcome of tests ........................................................................................................... 75 5.1.3 Analysis of test data .....................................................................................................75

5.2 Load carrying capacity ..........................................................................................................76

5.2.1 Introduction ..................................................................................................................76 5.2.2 Test specimen configuration ........................................................................................76 5.2.3 Adhesive selection ........................................................................................................ 76 5.2.4 Specimen construction .................................................................................................76 5.2.5 Test results and observations ........................................................................................77

5.3 Numerical studies ..................................................................................................................77

5.3.1 Introduction ..................................................................................................................77 5.3.2 Finite element modelling of the ‘Small scale’ test model ............................................77 5.3.3 Finite element modelling of the ‘Large scale’ test model ............................................ 78 5.3.4 Parametric studies ........................................................................................................ 79

6 Joint projects – case studies ........................................................................................................81

6.1 Glass roof: Design of the r oof beams ....................................................................................81

6.1.1 Description of the construction .................................................................................... 81 6.1.2 General information .....................................................................................................81 6.1.3 Pre-design with diagrams of the design guide ..............................................................82 6.1.4 Design according to Pischl ...........................................................................................82 6.1.5 Calculation with FE-methods .......................................................................................83

6.2 Facade structure of a café at the sea ...................................................................................... 84

6.2.1 Description of the construction .................................................................................... 84 6.2.2 General information .....................................................................................................85 6.2.3 Pre-design with diagrams .............................................................................................85 6.2.4 Design according to Pischl ...........................................................................................86 6.2.5 Design with FEM ......................................................................................................... 87

6.3 Solved example based on modified Möhler’s method .......................................................... 88

7 Design Guidance .......................................................................................................................... 91

7.1 INTRODUCTION ................................................................................................................91

7.1.1 Innovative steel glass structures – Application and benefits ........................................91

7.1.1.1 Hybrid steel-glass structural beams and columns ....................................................91 7.1.1.2 Glazed steel frame building facades ........................................................................ 91

7.1.2 Architectural considerations ......................................................................................... 91 7.1.3 Structural considerations ..............................................................................................91 7.1.4 Scope of the design guide .............................................................................................92

7.2 COMPOSITE STEEL -GLASS STRUCTURES AND STRUCTURAL MEMBERS ........ 92

7.2.1 General applications ..................................................................................................... 92

7.2.1.1 Internal environments .............................................................................................. 93

7.2.1.2 External environments .............................................................................................93 7.2.1.3 External building facades ......................................................................................... 94


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7.2.2 Requirements for fire resistance ................................................................................... 94 7.2.3 Fabrication .................................................................................................................... 95 7.2.4 Innovative uses .............................................................................................................95

7.3 MATERIAL SELECTION ...................................................................................................96

7.3.1 Requirements for the selection of materials .................................................................96 7.3.2 Steel .............................................................................................................................. 96

7.3.3 Glass ............................................................................................................................. 96 7.3.3.1 Mechanical requirements .........................................................................................96 7.3.3.2 Material properties ...................................................................................................96 7.3.3.3 Actions .....................................................................................................................97 7.3.3.4 Allowable capacity ................................................................................................... 97 7.3.3.5 Choice of the type of glass .......................................................................................99 7.3.3.6 Exemplary reference values .....................................................................................99

7.3.4 Adhesives ...................................................................................................................100

7.3.4.1 General ...................................................................................................................101 7.3.4.2 Stiffness, strength, ductility ...................................................................................103 7.3.4.3 Ageing behaviour ...................................................................................................103

7.4 MATERIAL PROPERTIES OF ADHESIVES .................................................................. 104 7.4.1 Methods used to determine adhesive mechanical properties .....................................104

7.4.1.1 Tension tests...........................................................................................................105 7.4.1.2 Shear or block shear tests .......................................................................................107 7.4.1.3 DMA test ................................................................................................................ 109 7.4.1.4 Ageing tests ............................................................................................................109

7.4.2 Material and mechanical properties ........................................................................... 110 7.4.3 Surface preparation ....................................................................................................111 7.4.4 Quality ........................................................................................................................112 7.4.5 Proposition of qualified adhesives .............................................................................113

7.5 DESIGN OF HYBRID STEEL-GLASS BEAMS ..............................................................113

7.5.1 Joining geometries ...................................................................................................... 113 7.5.2 Analytical models ....................................................................................................... 114 7.5.3 Preliminary design and pre-analysis tables ................................................................114 7.5.4 Detailed design ...........................................................................................................120

7.5.4.1 Loads ...................................................................................................................... 120 7.5.4.2 Material characteristics .......................................................................................... 120 7.5.4.3 Design with hand calculations ............................................................................... 120 7.5.4.4 Design with FE-calculations .................................................................................. 122 7.5.4.5 Design of global stability .......................................................................................122

7.5.5 Design of connections ................................................................................................ 123 7.5.6 Robustness requirements ............................................................................................124

7.5.7 Long-time behaviour ..................................................................................................125 7.5.8 Fabrication (Manufacture process) .............................................................................126 7.5.9 Economic considerations ............................................................................................127

7.6 DESIGN OF STEEL SUPPORTED GLASS FACADES ..................................................130

7.6.1 Design procedure sequence ........................................................................................ 130 7.6.2 Layout and configuration ........................................................................................... 130 7.6.3 Choice of glazing .......................................................................................................131 7.6.4 Glazing panel design – Thickness of glass plate ........................................................131 7.6.5 Adhesive selection ...................................................................................................... 131 7.6.6 Dimensioning of the adhesive ....................................................................................131 7.6.7 Design of the steel components ..................................................................................131

7.6.8 Determination of in-plane horizontal loads acting on building wall .......................... 132 7.6.9 In-plane stiffness of a glazing façade panel ...............................................................132 7.6.10 Check façade panel under Serviceability and Ultimate limit states ........................... 133


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7.6.11 Refinement of diagonal member in braced frames.....................................................133 7.6.12 Robustness .................................................................................................................. 133 7.6.13 Fabrication and manufacturing ................................................................................... 134 7.6.14 Economic considerations ............................................................................................134 7.6.15 FE modelling ..............................................................................................................135

7.7 RECOMMENDATIONS FOR QUALITY CONTROL .....................................................135 Conclusions ......................................................................................................................................137 Exploitation and impact of the research results ............................................................................... 140

List of figures and tables ....................................................................................................................144

List of acronyms and abbreviations .................................................................................................. 148

List of references ................................................................................................................................ 150


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FINAL SUMMARY

Steel-glass constructions are increasing popular in modern architecture and the need for research in thisfield is significant. Both materials are architecturally synergistic materials in modern building designand are frequently used in facades, roofs, atria, canopies, walkways and other expressive forms ofdesign.

Steel is a predictable, well researched material for structural applications, whereas glass is an elastic and brittle material without any capacity for plasticizing, less well researched for structural uses and notamenable to simplified design.

The innovative approach here is using adhesive bonding to connect steel and glass elements for new,hybrid structures, which offer main advantages regarding load carrying capacity, stability behaviour,ductility and robustness. Thus the research project “Innovative Steel-Glass-Structures” (INNOGLAST)aims at the development of new and innovative steel-glass construction in respect to architectural,static-structural and fabrication criteria. For this two different examples are used:

1. Hybrid steel-glass beams

2. Steel-supported glass-systems

The development comprises the technical design of the details and investigations on the global and localstatic behaviour of such structures identifying the limits of the applications and find solutions for detailslike load introduction and connection points. For architects and engineers, the research present newsteel-glass elements which fulfil architectural and technical needs regarding design, loading capacity,durability and robustness.

Bonding technology

The bonding technology is a modern solution to connect different materials without energy input orweakening the cross section by holes. Bonding is used in other industry such as automotive or aviationindustry as well as the ship building industry with great success and has been established there foryears. The connection of steel sheeting or steel profiles and glass structures has been already applied

there, for example bonding the windscreens of cars, busses, trucks or trains on the load bearingsubstructure in order to increase the global torsional stiffness.

On the contrary in civil and façade engineering bonding is still predominantly used for sealingapplications or for bonding of structures with minor structural importance (tiles, parquets, dowels and bolts). One positive example for the use of structural bonds in civil engineering is the reinforcement ofconcrete structures with bonded steel or CFRP sheets. In façade engineering structural silicone glazing(SSG) applications with “structural” silicones have been successfully applied since 30 years, but in themajority of cases with additional mechanical retaining systems. That is why and where theINNOGLAST project comes in.

First of all, compared to conventional joining techniques in steel constructions like bolted connectionsor welding, bonded joints have the following major advantages and disadvantages:

+ Connection of materials with different properties (hybrid connection of steel and glass)+ Components are not weakened by holes (simultaneous saving of costs)

+ Constant stress propagation caused by a continuous connection

+ Vibration damping due to the lower Young´s-modulus of the bonding

+ Saving of weight caused by the absence of bolts and the use of thinner raw material

+ Economy of space, lightweight construction

─ Lower resistance compared to the connected materials

─ Elaborate manufacturing process and surface pre-treatment

─ Durability influenced by ageing, high temperature, humidity and UV-radiation

─ Long-term behavior influenced by creeping


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The disadvantages must be balanced or minimized by an appropriate joint design such as sufficient bonding geometries, appropriate loadings (predominant shear, avoidance of peel loadings) and adequateadhesive selection. Especially in other application fields a large number of bonding materials isavailable that would be appropriate for use in structural steel applications, whereas cold hardening two-component adhesives are the most practical for structural application for civil engineering aspects.

Bonding of steel and glassCompared to other industries the requirements of bonded steel-glass-joints for structural engineering insome issues are differing: Regarding the projected steel-glass structures the thickness of the componentsis comparatively thick (steel: 5 – 10mm, laminated glass: 10 – 30 mm), the materials have differentthermal dilatations and the tolerances are lower (up to 1 mm or more).

Since years, the glass architecture uses adhesives for “structural sealant glazing”: facades panels areconnected by silicone with adapter frames. Silicon is also used to realize the sealing of insulated glass.Having regard to the process ability of the adhesive and the particularities of the connection, onecomponent or two component silicones are adapted adhesives to realize the connection of the newhybrid steel-glass-beam because

- the viscosity is sufficient low

- the pot time is long enough- they are suitable for bonding glass as well as stainless steel after removal of oxides

- the material properties are more or less constant for the normal construction temperature from -

20°C up to 80°C.

As flow and creep of silicon is rather high further constructive measures have to be provided likesockets to ensure sufficient robustness. In addition the structural effectiveness such as stiffness or load bearing capacity is not very high, but can be often compensated by large bonding areas. Another veryimportant fact is the outstanding ageing and corrosion resistance and durability of silicones.

On the other side there are comparatively “new” adhesive systems which can take over a real static-structural function, like epoxy resins, acrylates or polyurethanes. These adhesive provide a wide range

of different stiffness, strengths and ductility and so are in the focus of the research withinINNOLGAST.

Within the project adhesive systems with different stiffness and strength values are preselected beingapplicable for steel-glass connections. Depending on the mechanical values, the ageing and application behavior as well as the curing behavior, eleven adhesives are finally chosen and extensively used in this project for small-scale and large-scale specimen. The choice of adhesive reaches from very stiff epoxyresins (3M – DP 490, Sika – SikaDur 30) to high and medium stiff polyurethanes (3M - DP 610,Kömmerling – Körapur 666) and acrylates (Delo - GB 485, Sika – SikaFast 5211). The selection goesfurther to very elastic, but sustainable polyurethanes (Henkel - Terostat 8630, Sika – SikaFast 7550,Sika – SikaTack-Plus Booster) down to the well-known and established silicones (Dow Corning – 993,Sika – SikaSil SG 500) as references.

For these adhesives the mechanical values for tension and shear loading are determined and most of

them are implemented in FE calculations properly. Besides that the choice of appropriate bondingtechniques and adequate manufacturing processes is matter of the research to guarantee best performance of the steel-glass-structures. As surface preparation and pre-treatment methods are not inthe focus of the project, it is reverted to combined adhesive-primer systems suggested by the adhesive producers. Ageing and durability aspects are also treated in a limited way to get a rough estimation ofthe general behaviour.

The hybrid steel-glass construction

Glass is currently strongly in demand for many applications, moreover new forms of glazing arecontinuously being developed having improved thermal and structural properties. In modern steel-glassarchitecture pure glass fins are increasingly used as beams and columns due to their extraordinary

design, but have disadvantages because of static-constructional aspects such as global instabilities and


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the complex connections between glass fins and the adjacent structural elements. Thus, steel mostly provides the support structure for the glass elements in many conceivable applications.

The new hybrid steel-glass beam consists of steel flanges and a glass web and is an intelligent steel-glass construction for modern architectural design, combining the favoured materials steel and glassoptimally in view of static-structural as well as architectural aspects. A key aspect of this developmentis the detailing of the steel glass interface and the selection of a suitable bonding material.

Within INNOGLAST hybrid façade elements and floor girders are developed, where flanges of steeland webs of glass are assembled to I-beams using adhesive connections. This allows for a smooth loadintroduction into the glass panes. The shear force is carried by the glass web, whereas the bendingcapacity of the hybrid beam is significantly increased by slender steel flanges compared to the pureglass pane. The shear forces between steel and glass are only sustained by the adhesive between them.To maximize the exploitation of steel and glass the adhesive therefore, on the one hand has to ensure anadequate stiffness but on the other hand must be soft enough allowing for a reduction resp.redistribution of stress peaks or other constraints. However the load-bearing capacity of such beams isgoverned – apart from the mechanical and strength characteristics of the adherent - by ageing,temperature and creeping. Therefore – besides the static-structural behaviour of the entire hybridstructure – the research is focussed on the adhesive connection and its mechanical behaviour. Thisincludes the mechanical behaviour of the adhesive itself as well as the connection behaviour of the

whole linear joint. It proved to be useful to investigate the general behaviour of the connection by smallscale tests and later on to carry the results over to large scale tests in the project progression.

The connection between steel flange and glass web can be achieved by butt splice or channel bonding,or by using additional L- or U-shaped profiles, which offer larger bonding areas, more ductility and provide a higher protection against ageing and corrosion, but complicate the fabrication and requireoptimized manufacturing methods. Especially the different joining geometries show a great complexityregarding production, testing and calculation by FE method. The geometries with butt-joint bonding andU-profiles prove to be the promising ones and are followed-up with large scale tests.

One major design principle for the joint is creating constant stress propagation between steel and glass

and especially avoiding stress peaks in the glass panes. The intensive adhesive tests reveal that somevery stiff epoxy resins can generate glass breakage if the bonding quality is not adequate. Polyurethanesdescribe an economic alternative between very stiff, brittle adhesives and rubber-like silicones withoutimportant bearing capacity. By means of standardized tests the potential of up to date adhesive systemsis pointed out and the potential of these systems is demonstrated. Nevertheless silicones hold their widefields of application especially in SSG systems because of their outstanding elasticity and ageingresistance. On the other hand there are predominantly polyurethane systems which keep up or even passthe competences of silicones.

Besides the adhesive connection the surface preparation is very important for the durability and bearingcapacity of the connection. For steel surfaces a preparation by sand-blasting followed by degusting anddegreasing is recommended, for glass degreasing and the use of special glass or UV-protecting primers

is necessary. The choice of adhesives and primers should be coordinated with the adhesive producers.With seven selected adhesives a large number of small scale push out tests are successfully performed.Hereby the load is divided in pure tension and pure shear to determine the load carrying behaviour for both cases. Originally the push-out tests are intended to provide the mechanical values of the adhesive joint, but the tests reveal an important influence of the lateral contraction on the adhesive carryingcapacity. That is why additional standardized adhesive tests are needed. Although the push-outspecimen are uniaxial subjected to shear or tension, the stress-strain behavior of the adhesive geometryis not completely obvious. Due to the lateral contraction and the more or less pronounced hydrostaticstress of state (depending on the adhesive system) the fracture is not definitely caused by the uniaxialloading alone, but also by the reduced lateral contraction of the joint. Therefore push-out tests representa kind of very helpful component tests but not simple tests with completely uniform stress distribution.

Hereby the tension push-out tests exhibit a minor comparability with standardized test specimen thanshear push-out tests. On the other hand the scale effects are already included in push-out tests andtherefore they are more representaive for the carrying behavior of large-scale components.


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For the hybrid beams first analytical models are developed. The work was divided in two parts. Theformer is aimed to determine analytical model for hybrid beams with glass web made of one glass pane.Möhler’s and Pischl’s methods are verified by full-scale experiments and numerical analysis. Bothapproaches are suitable for linear adhesives in bonded connections between the glass web and steelflanges. The modified Möhler’s method is derived for non-linear behaviour of adhesives in case ofsemi-rigid shear connection. The second part is pointed to the analytical model for hybrid beams withwebs composed from several panes. The solution is based on different approaches. According to theexperimental results, an analytical model based on truss analogy is used. The developed analyticalmodels are suitable as a tool for the preliminary design of hybrid beams.

In comparison to glass fins the hybrid steel-glass girder achieves a higher load carrying capacity andstability problems are considerably reduced. The steel-glass beam offers best possibilities forconnecting structural components at the steel flanges easily and it achieves an astonishing filigreedesign. Compared to common I-girder made of steel the hybrid steel-glass girder enables improvedarchitectural design due to the clear-transparent glass web especially regarding light-weightconstructions and facades. Experimental investigations of the load carrying capacity of the hybrid steelglass beams are carried out. Six short time tests and one large scale test are performed at thelaboratories of TU Dortmund. Additional tests are carried out at the laboratories of Czech Technical

University. Due to detailed measurements of strains and deflections important information about thecarrying behaviour of bonded steel glass beams is gained. All data (including information about thefabrication) is documented. The results of large scale tests are used to develop the design model and thedesign guidance.

In order to recalculate the test results and to obtain design recommendations, a finite element model forthe steel-glass beam is developed in ANSYS, taking into account different geometrical forms andconnection details. Two models are developed: a simplified model with shell elements and a detailedmodel with solid elements. Different material properties of glass and steel and the characteristic of the bonded connection are included. Elastic models and non-linear material models are used for theadhesive. The FE-Model is then calibrated by large scale tests. Parametric studies are carried out andwere used to enlarge the information on carrying behaviour of steel-glass-beams which is gained duringthe large scale tests.

Additional full-scale experiments of hybrid beams with glass web divided to several panes are carriedout at CTU with the same test setup used in Dortmund. In total nine test specimens are analysed toobtain residual load bearing capacity of beams as well as to verify robustness. The set of experiments,the length of beam and cross-section are the same as for test of load carrying capacity. The type ofconnection between web and flanges, adhesive and contact of glass panes are changed to determinestatic behaviour under bending with regard to different conditions. Deflections as well as stressdistribution along the cross-section are measured. These dates are used for the development andverification of analytical and design model. It can be summarized that the robustness and ductility of thehybrid beam is significantly higher than for a simple glass pane. Another increase of robustness can beachieved by using laminated glass panes. According to requirements of redundancy the glass-webshould consist of laminated glass.

Following the large scale tests full scale stability tests on flexural buckling and lateral torsional buckling are performed to investigate the global stability behaviour of such hybrid structures. Due totheir slenderness and high utilization they can be susceptible for stability problems. The tests onflexural buckling show a high utilization of the beams and a considerably increased stability resistanceonly because of the slender steel flanges. Hereby the maximum buckling loads for most of the specimenis independent from the choice of adhesive, in this case a stiff epoxy resin and elastic polyurethane.Furthermore the ductility is significantly increased compared to the glass pane alone. Summing up thelateral torsional buckling tests it can be stated that due to the small number of tests no resilientconclusion can be drawn. Because of the high testing effort and the complex test setup with moveable bearings under high loads the tests can only be regarded as first trail tests. It turned out to be verydifficult to force the beam into the first mode shape and to prevent the beam from falling into thesecond mode shape, because the moveable supports tend to move away from each other and not in the

same direction.


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Moreover the steel-glass beams were optimised in regard to an architectural design. Appropriate fieldsof application for hybrid steel-glass-beams regarding the conditions on site are examined and presentedin photorealistic renderings. Furthermore the creative potential of steel-glass-structures in buildingswith ambitious architecture is emphasised with examples. The distances of beams are analysed withregard to the architectural appearance and conventional axle dimension in commercial, residential andindustrial buildings.Basic constructional details, for example connection points, bearing points, load introduction points are

worked out and presented in construction drawings and renderings. Together with the static structuralanalyses the results are used to achieve a multi-disciplinary optimised product.

Exemplary design procedures are shown for specific use of hybrid beams in structure. The calculationof hybrid beams as members of transparent roof structures as well as stiffening fins of glass wall aredescribed step by step. Three different kinds of adhesives were used for the design examples. Eachexample is based on preliminary estimation of cross-section, supported by pre-design graphs or tables.The proposed cross-section dimensions are accurately evaluated by different analytical methods in thefinal step and also supported by FE analysis.

Steel-supported glass-systems

Steel supported glass-systems are already used in ambitious architectural designs, but the design ruleshave not kept pace with these new developments. The technology of steel and glass has grown witharchitectural demands, but an agreed basis of design is still missing. Although the in-plane stiffness ofglass is well-known, there are no design guidelines and only recent research is considering thefavourable material properties of glass to improve the design of steel-glass systems. Therefore, thescientific approach concentrates on the analysis of structural performance using FE-analysis and full-scale tests in order to optimise steel-supported glass systems by optimizing interaction of the differentmaterials. Based on these physical tests and FE analyses an analytical method is developed.

The project investigates the interaction between steel supporting structures and façade glazing. Steelsupported façade glazing systems, consisting of hollow tubular members are investigated using acombination of physical testing and numerical modelling.

Commonly the connection between the steel members and the glass is usually made by articulated jointsusing brackets or attachments that are ‘point’ connections. These connections provide for limitedfreedom of movement, and therefore it is necessary to design the structure to facilitate installationtolerances and to allow for transient and longer term movements. The system should also fail “safe” sothat failure of one element should not lead to collapse or failure over a disproportionate area.

Within INNOGLAST, adhesive bonded connections applied continuously along the edges of theglazing have been considered rather than the ‘point’ attachments currently used. The results show thatthe proposed steel-supported glazing panels with adhesive bonded connections are viable providing thatadhesives are used which have appropriate strength and stiffness properties that can resist andaccommodate the deflections imposed on the glazing façade resulting from horizontal loads acting onthe building frame (approximately 15 mm horizontal movement between building floors). Theadhesives recommended are therefore the silicone based adhesives (Dow Corning DC 895 and DC 993

or similar) and also the more flexible polyurethane adhesives (Sika SikaForce 7550 or similar).Following the calibration of the testing of the steel supported glazing panel with the FE modelling, thehorizontal in-plane shear stiffness of façade panels, for the considered adhesives, have been obtainedfor a range of panel sizes, typically of building storey height (3-4m) and of width 1,8-3,0 m. Thisreadily enables an assessment to be made to determine the proportion of the horizontal load from the building frame that is accommodated by the glazed façade. Analysis of the proportioning of thehorizontal loads between the glazing façade and the steel building bracing systems shows that asignificant proportion of the load can be taken by the glazing panels without exceeding in-servicedeflections of the building frame and hence the façade. Consideration can therefore be given tooptimising the façade and building design and in certain cases to potentially reducing the size of the bracing members. However, a design philosophy must be postulated such that the serviceability limitstates are satisfied and that robustness considerations for the façade are met.


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A connection detail for the steel supported glazing façade was developed. Consideration was given to acontinuously bonded adhesive based steel-glass connection in which the adhesive was applied along thecircumference of the glazing panel. The connection detail proposed was tested to investigate the in- plane shear and peeling behaviour of the adhesive based connection. It was found that for the range ofin-plane deflections encountered in building glazed facades, adhesive properties at small deflectionswould be adequate for further analysis. Tests were performed on silicone, polyurethane and epoxy based adhesives, however, it became obvious that only the silicone and polyurethane adhesives would

be appropriate for glazing facades.Finite element analyses were performed to model and calibrate the connection tests performed. It wasfound that a linear force versus displacement model relationship adequately modelled the behaviour inthe connection tests and the adhesive properties could be defined by quoting the shear modulus of theadhesive near zero displacement and the corresponding Poisson´s ratio of the adhesive. Young’smodulus was obtained based on the well-known relationship between the adhesive’s shear modulus andPoisson´s ratio.

The connection detail was optimised by proposing the most appropriate adhesive to be used for the steelsupported glazing façade. The silicone adhesive (Dow Corning DC 993, 2 part adhesive) was proposedhowever, it was observed that similar silicone adhesives (1 part silicone DC 895) could also be used. Inaddition the more flexible polyurethane adhesive (SikaForce 7550) was also found to be acceptable.

Adhesive properties to be used in design were determined for the three prospective adhesives.

An analytical model was developed for the analysis of the steel supported glazing façade subjected toin-plane horizontal forces. The model comprised the determination of the in-plane stiffness of a steelsupported glazing panel based on the physical tests and finite element analyses performed on theglazing panel and the determination of the building bracing stiffness frame found in ‘simpleconstruction’ multi-storey buildings. The model determined the horizontal loads acting on the buildingframe which would need to be resisted in-plane by the bracing system and the glazing façade. Based onthe relative in-plane stiffness of the façade and bracing system the proportion of horizontal forces actingon the faced is determined. This analytical tool therefore enables the designer to design the façade forserviceability and ultimate limit states and also for robustness requirements.

Large scale tests were performed to investigate the in-plane behaviour of the steel supported glazing panel (modelling the ‘lozenging’ effect of the glazing panels in the plane of the façade). The compositein-plane action between the steel support structure and the glass plate was observed and the loadcarrying capacity determined. The test specimen was 2m by 2m in size. A review of all the tests showedthat as the in-plane load was applied to the steel windpost, the force was transmitted through theadhesive causing the glass panel to move as a stiff element, where the panel underwent in-planetranslation and rotation. No out-of-plane movements in the glass panel were observed, owing to thesignificant flexibility inherent in the adhesive. The in-plane behaviour of the adhesive was investigated by observing the relative displacement between the loaded tee section and the edge of the glass panel.The tests showed that a linear relationship existed for the adhesive for the range on in-planedisplacements expected for the glazing façade. Various loading rates were applied to the specimen

together with a test modelling repetitive loading.A finite element model of the large scale test specimen was developed and analysed to replicate the behaviour of the large scale test specimen undergoing in-plane loading. The FE model used theadhesive material properties based on the results from the connection tests. A comparison of the panelload-displacements obtained from the FE analyses showed close agreement to those observed in thelarge scale physical tests, thereby proving the FE model. Using this proven FE model, a series of parametric studies were performed to obtain the panel stiffness for different sizes of glazing panelassemblies. Further FE analyses were performed to obtain panel stiffness for the other adhesives underconsideration.


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13

Design Guidance

Since hybrid steel-glass structures are a new development almost none guidance exists on the design ofsteel-glass beams and steel-supported glass systems. Therefore the main results of INNOGLAST are bundled and summarized in general design guidance for steel-glass structures.

Assistances for the choice of adhesives are developed and included in the design guide. Besides the

choice of adhesives the determination of mechanical values is shown and advice for the examination ofthe ageing behaviour is given. Reference values for the adhesives and FE material laws are proposed.

For the hybrid steel-glass beams first design rules in compliance with the basic rules for structuraldesign and steel design in the Eurocodes are developed, but are not secured statistically for all cases.Especially a safety concept for adhesives is missing. On the other hand constructional details and staticoptimisations are performed and prepared for the practical application (design aids, float charts, best practises) to ease the use and to support the implementation of the results in practise.

These design aides are based on two analytical methods for the design of bonded beams. The methodaccording to Möhler is a simplified method for the calculation of flexible composed sections and isqualified best for pre-design since it is easy to handle. The method according to Pischl is more complex but generally provides more accurate or even exact solutions. Both models are useful for adhesivesconsidered as linear elastic. For a lot of semirigid adhesives, this assumption cannot be applied without

restrictions, because their stiffness is changing during the range of load. Therefore modified Möhlersmethod was developed to describe the behaviour of the beam including this changeability.

For hybrid beams with glass web composed from several panes different analytical model has to beused because of the completely different stress distribution and carrying behaviour under increasingload. Here the truss analogy has high potential to be an accurate tool for the complex description of thiskind of beam.

Depending on the complexity of the structural system hand calculations or numerical calculations aresuitable for the detailed design of hybrid beams, Referring to the different calculation methodsinformation are included in the design guide.

Results concerning stability problems, robustness, long time behaviour, fabrication and economicefficiency of hybrid beams were also included in the design guide and give the user aids for the

development of suitable optimised beams.

For the steel supported glazing facade the design guidance was developed based on the physical testing,the FE modelling and the development of the analytical model. The design guidance provides a step bystep procedure for designing the steel supported glazing panel for out of plane loading and an analyticalmethod for determining the proportion of the horizontal in-plane loading that the façade will need tocarry. The guidance also provides information relating to the design of the façade for in-serviceconditions such that acceptable deflections limits are not exceeded. Robustness requirements for theglazing façade is also discussed.

The following investigations are finished successfully and are contained in the design guidance:

- Optimization of the connections (adhesives, geometry of the joint) in regard to the design,loading capacity, load carrying behavior, the quality of fabrication, the attributes of the bonding

(elasticity, durability, etc.)

- Development of a statical model taking into account the elastic joint between the steel and glass

- Determination of the load carrying capacity of the steel-glass structures under short-term loads.

- Estimation of the load carrying capacity of steel-glass-structures with regard to stability

phenomenon

- Analysis of redundancies in case of breakage of one or more glass panels

- Constructional detailing of elements like connection, bearing and load introduction points

- Case studies

- Design aids - Architectural criteria


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The following items are to be investigated in future more intensive:

- Design rules for stability behavior

- More detailed analysis of the ageing resistance of adhesives

- Creeping of adhesive connections

- Development of a general safety concept for bonded connections

- Fatigue behavior of bonded structures


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15

SCIENTIFIC AND TECHNICAL DESCRIPTION OF THE RESULTS

Objectives of the project

Due to an rising demand of architects for more transparency and mergence between indoors and

outdoors glass in construction plays an increasing role not only as façade cladding or windows but alsoas load bearing, structural element. Glass beams, glass columns or bracing façade elements, e.g. large-scale glazing for single or double skin façades, for balustrades, roof glazing or transparent flooring aresuch examples to realize those architectural attractive transparent structures. Current research work [1]-[4] and realized projects [5], [6] underline the relevance of this topic.

In contrast to the ductile material behaviour of steel glass fails without a letter of indication.Additionally the limited capability for stress reduction or redistribution by plasticizing requires a precise design of structural details. Here bonded hybrid structures are favourable where each materialaccording to its material properties is used in an optimised way. This can only be achieved by assigningthe adhesive a real load-bearing role.

The aim of the project INNOGLAST was the development of new and innovative steel-glass-structuresin respect to architectural, static-structural and fabrication criteria. Different types of steel-glassconstructions were analysed or even newly developed focusing on an optimal structural interaction between steel and glass. Thus, the researches comprised new hybrid steel-glass beams, consisting ofsteel flanges and a glass web, and steel-supported glazing systems.

Hybrid steel-glass-beams

Within the scope of this European research project hybrid façade elements and floor girders should bedeveloped, where flanges of steel and webs of glass are assembled to I-beams using adhesiveconnections. This allows for a smooth load introduction into the glass panes. The shear force is carried by the glass web, whereas the bending capacity of the hybrid beam is significantly increased by slendersteel flanges compared to the pure glass pane. The shear forces between steel and glass are only

sustained by the adhesive between them. To maximize the exploitation of steel and glass the adhesivetherefore, on the one hand has to ensure an adequate stiffness but on the other hand must be soft enoughallowing for a reduction resp. redistribution of stress peaks or other constraints. However the load- bearing capacity of such beams is governed – apart from the mechanical and strength characteristics ofthe adherent - by ageing, temperature and creeping.

One main advantage for the use of adhesive is that the joint between glass web and steel flange made by bonding achieves preferably constant stress propagation in the glass. Therefore the choice of adhesiveshas a central role in the project because the load carrying-capacity of the composite section depends primarily on mechanical material characteristics of the joint. Furthermore to ensure a traceable qualityand workmanship of the adhesive connection the production process beginning with the storage of thecomponents, going on to the surface pre-treatment to the point of manufacturing and post processing of

the bonded joint has to be defined and controlled clearly.

Steel-supported glass-systems

Investigations were carried out analysing steel-supported glazing systems with special regard on ovaltubular members respectively. The connection between the steel members and the glass is usually made by articulated joints using brackets or attachments that are directly made on the structure. These brackets provide for limited freedom of movement, and therefore it is necessary to design the structureto facilitate installation tolerances and to allow for transient and longer term movements. Alternatively, bonding is used within this project to join steel and glass. The steel-glass systems should also fail “safe”i.e. failure of one element should not lead to collapse of the system.

The project duration was originally intended to be 36 months. The working programme was divided

into seven working packages, the proposed programme bar chart is shown Table 0-1.


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Table 0-1:

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and wor

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beam. H

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systems

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tests and

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16

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18

2008 it was almost impossible to find a producer who felt up to produce such a small order. To makematters worse one adhesive had delayed delivery for 4 months, so that some push-out specimen couldnot be manufactured until December 2008. This also led to delay for the determination of themechanical values by tension and pressure shear tests of the concerned adhesives.

The push-out-tests were originally intended to determine the mechanical values suitable for finiteelement analysis (WP 1.2). It transpired that the push-out-tests were very useful to classify andcharacterize the bearing behaviour and the load carrying capacity of different connection types, but thatthese tests mainly because of size effects are not practical to identify clear mechanical values for FE-element analysis. On that score additional small scale tests were defined to specify the mechanicalvalues for pure shear and tension loading and to obtain workable input values for the FE analysis. Thesetests were standardized tension tests on dumbbell specimen and modified block shear tests. Furthermoreaccelerated ageing tests were carried out and the glass transition temperatures were determined bydifferential scanning calometry.

Because of the extensive additional adhesive tests and the delayed delivery of the required small-scaleglass specimen the originally proposed schedule for this WP couldn´t kept.

The objectives of WP 1.2 were to enlarge the data determined by push-out testing (WP 1.1) and toanalyse the connection details by FE methods. Hereby the intended working plan was slightly modified, because it was not able to derive appropriate mechanical values from push-out tests suitable for FE

analysis. The standardized tests on the adhesive itself led to better values, but revealed, that the stressstate as well as flow and fracture limit is highly governed by the hydrostatic state of stress in theadhesive. These effects could not fully be modelled with commercial state-of-the-art FE software likeANSYS or ABAQUS, but it is possible to use an approximate solution. That was why differentadditional optimization loops were necessary in this WP to fulfil the intended work programme.

Within WP 1.3 the optimization of the connection detail and the development of design rules for the bonding details used for the hybrid steel-glass-beams and the steel-supported glass-systems were done.Especially all the knowledge regarding the manufacturing and fabrication of bonded connections gainedat all institutes were collected as well as the mechanical values of all adhesives being used.

The aim of WP 2 was to optimise the steel-glass structures in regard to an architectural design. By theway of exemplary uses cases the application and design of new steel-glass-construction forms due to the

use of adhesives was examined and appropriate fields for the application of hybrid steel-glass-beamwere demonstrated. Photorealistic renderings show possible fields of application from an architectural point of view. Furthermore this WP is focussed on the development of detail sketches which wereappropriate for the material combination steel-glass and the adhesive bonding.

In WP 3.1 analytical models for the calculation of the hybrid steel-glass-beam beams were developed.Analytical models for elastic connected sections can be used for beams made of one glass panes. Themodel for beams with a web composed of several glass panes is based on a “Vierendeel”- or truss-model. All models were verified by finite-element-analysis. Hereby a new analytical model withiterative adapted adhesive stiffness was developed.

WP 3.2 contains the development of a simple Excel-based analytic model for the calculation of steel-supported glass-systems.

The intention of WP 4.1 was the experimental investigation of the load carrying capacity of the hybrid

steel-glass-beam. Six full scale tests on beams with 4 m span using four adhesives of differentstiffness’s and strength classes were carried out and one full-scale long-term creeping test was performed. Thereby the construction details of the beam were configured and the fabrications of the beams were documented.

Due to a heavy rainfall going along with a water ingress in the testing laboratory of UniDo themeasurement equipment was badly destroyed, so that the test were significantly delayed, see Table 0-2.

An additional set of full-scale tests was carried out at CTU with the same experimental set-up, similardimensions of cross-section and different kind of adhesives.

The objective of WP 4.2 was to investigate the global stability behaviour of the hybrid steel-glass-beam.Global instabilities which may occur for the hybrid steel-glass girder are lateral-torsional buckling of beams and flexural buckling of columns. Due to the very elaborate and complex stability tests the

number of test had to be limited and therefore the interaction between both instabilities cannot clearly


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19

be evaluated. Local instabilities such as local plate buckling were neglected and constructional excluded by the choice of steel-flanges and glass web geometries which comply with the limit b/t-ratios.

In this WP six flexural buckling tests and four lateral flexural buckling tests with three differentadhesives were performed to get a first estimation of the stability behaviour of adhesively bonded steel-glass beams.

The objective of WP 4.3 was to carry out numerical studies to verify the test results of WP 4.1 and WP

4.2 and to enlarge the results by parameter studies.WP 4.4 deals with the investigation of robustness of hybrid steel-glass beams with glass web divided toseveral panes. In total nine test specimens were analysed to obtain residual load bearing capacity of beams as well as to verify robustness. The connection type between web and flanges, adhesive andcontact of glass panes were changed to determine static behaviour under bending with regard to thedifferent conditions. Because of the delayed WP 4.1, which serves as a basis for this WP, the robustnesstests were also delayed.

WP 5.1 was focussed on the investigation of the load carrying capacity and the bearing behaviour ofsteel-supported glazing-systems. Large scale tests on bonded steel-glass elements under point loadingwith different magnitudes were performed and evaluated. The results were modelled numerically withthe FE method in WP 5.2.

In WP 6 all important results gained within this project were summarized and design propositions were

given. Because of the minor experience of bonded structures in practise the design guidance shouldcollect best practises, simple design suggestions and user aids for innovative steel-glass structures inorder to assist architects and engineers in their practical work and to introduce bonded steel-glassstructures in practise.

Finishing purpose of WP 7 was to perform case studies or joint projects implementing the resultsachieved to demonstrate the possibilities for applications and to support the dissemination in practise.

Description of activities and discussions

The general approach was developed in an early stage and can be taken from Table 0-3. According tothat the project was divided in eight main steps. First of all basic requirements for the adhesive joint

were derived, which arise from the overall context of the structure (I.). Based on these requirements theadhesive geometries were selected (II.) and appropriate adhesives were chosen (III.). For theseadhesives the mechanical values were determined by means of standardized tests (IV.). The values can be used for FE analysis. Then, separated in shear and tension loading, small scale push put tests weredeveloped regarding the initial basic requirements of the joint (V.). By these push out tests shear andtensions capacity were determined (VI.). In a next step the results were transferred to largercomponents, including bending tests and stability tests accompanied by FE calculations (VII.). At theend a design guidance was developed to give assistance for designing bonded steel-glass structures andto promote this new joining technique (VIII.).


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Table 0-3:

IV. De

VI. De

System

I. D

erminatio

T

. Develop

terminatio

Tensile te

atic approac

rivation o

II. D

of mecha

nsile tests

ent of s

n of tensil

ts

for INNOGL

basic req

esign of th

III. Select

ical value

sp

all scale te

significan

and shear

Te

20

ST

irements

e adhesive

ion of adh

s of the ad

ecimen

st specime

e concern

capacity

sile shear t

F

o the adh

geometry

sive

esives by

AWOK

(modified

(push ou

ng I.

y means o

sts

sive joint

means of s

block shear

ressure she

specimen

small sca

FE cal

tandardiz

tests

ar tests)

) with

le specime

culations

d


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ateral buck

VII. Tr

Bendi

Stabil

ling

VI

ansfer to r

ng tests

ity tests

Lateral

I. Derivat

21

eal structu

torsional b

ion of desi

ral elemen

ckling

n rules

s

FE-cal

FE-cal

culations

culations


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1 JOINING DETAILS AND SMALL SCALE TESTS

1.1 Selection of adhesives

As the choice of adhesives and the determination of the material parameters of the adhesives had acentral role in the project, the work realised in WP 1 was carried with high accuracy and took more time

than estimated in the proposal. Furthermore a basically new test setup for adhesive tests was developedand the knowledge of adhesives was considerably extended to execute the small scale tests reliably.

Concerning the choice of adhesives one major aim of this project was the investigation of adhesivessystems with higher stiffness and strength as provided by standard silicones. Silicones are generallyused in structural glazing facades, but offer here only little structural features.

Though a profile of requirements has been developed and was brought to a great number of adhesivecompanies, to obtain a wide range of applicative adhesives. From a set of 18 adhesives that weresuggested by the adhesive producers and that seemed to be appropriate (see Table 1-1), sevenrepresentative adhesives were finally selected.

The selection criteria for the general qualification of the adhesives and the main requirements are shownin Table 7-8. Table 7-9 attempts to classify common used adhesive systems regarding the applicabilityin INNOGLAST. This can only be done in a general manner, because especially polyurethanes show awide spectrum of different properties, but the valuation is generally valid for most of them. Figure 7-1shows the important relationship between Young´s modulus and elastic properties.

Table 1-1: List of suggested adhesives of the adhesive producers

Epoxy resin Polyurethane MS-Polymer Acrylate Silicone

2c 1c 2c 2c 1c 1c 2c

3M DP 490SikaTack

Plus3M DP 620

NSHenkel

Terostat 9399Delo GB 485 DC 895 DC 993

Körapox 551 3M DP 610Delo GB VE

56903DC 994

Körapox 558Henkel

Terostat 8630

SikaSil SG-

500

Körapur 666Henkel Loctite

5610

Körapur 842

SikaForce7550

First all adhesives were compared regarding their specific material properties and application behaviour, the possible ageing resistance and their applicability for joining steel-glass-connections. Thiscomparison was done on the basis of the producer’s specification and test results already available.Thereby the following exclusion criteria were applied:

-

Adhesives with application times shorter than a few minutes are rejected- Because of the joining geometry and the bond thickness humidity-curing adhesives are sortedout (predominant one component silicones)

- Adhesives with low viscosity and less stability on inclined surfaces are excluded

- Low temperature resistances and glass transition temperatures are not applicable

- Adhesive must have been successfully used for previous bonding of glass and steel (e.g. forglazing application in the automotive industry)

- The choice of adhesives must cover a wide spectrum of adhesive systems as possible

The final selection of adhesives is listed in Table 1-2. These adhesives are one the one hand subjected tomechanical tests (ageing test, tensile and pressure shear tests, see chapter 7.4.1) and on the other hand tosmall scale push-out-tests (chapter 1.3). Further information can be taken from these chapters.

The choice of adhesives had to find a balance between stiffness, maximum strength, possibleelongation, ageing and temperature resistance and processability of the adherent. To avoid an additional


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enlargement of the parameter field, the surface pre-treatment was limited and only primer system whichwere suggested by the producers and especially adjusted to the adhesives were used.

The stiff polyurethane systems such as DP 610 and KP 666 and the epoxy resin DP 490 behave verystiff and brittle and therefore are not qualified best. In addition the ageing resistance is not convincingin all cases. This statement not generally excludes adhesives based on epoxy resins, but it is stronglyrecommended to handle them carefully and to use them in an engineering-style manner. Especially theDP 490 had been successfully used in several other projects and offers great advantages and possiblefield of application. Comparing the six adhesive with the standard two component silicone DC 993, theSikaForce 7550 and the Terostat 8630 fulfil the tightrope walk best (see chapter 7.4.2 and 7.4.5).

Table 1-2: Overview of important properties of the selected adhesives (given by the adhesives producers)

Name DP 490 DP 610 KP 666 TS 8630 SF 7550 GB 485 993

Producer 3M 3M Kömmerling Henkel Sika Dow Corning Delo

Basis EP PU PU PU PU Acrylate Silicone

Componen

ts2 2 2 2 2 1 2

Screen

print

notnecessarily

yes yes desirable desirable nonot

necessarily

Primer Use of primer systems suggested by producersCuring

time7 days 7 days 10-36 h 5 h 4 days

60s (UV-curing)

7 days

Pot time 90 min. 10 min. 90 min. 30 min. 15 min. - 10-30 min.

Elongation

at break3,5 % 50 % 2 % 370 % 250 % 230 % 130 %

Colour black transparent beige black black transparent black

In the process of the INNOGLAST project additional adhesives were selected by CTU, because someof the adhesives were not available in Czech Republic and there was the good opportunity to workclosely together with the adhesive producer Sika, especially for manufacturing the large scale tests.

Therefore four additional Sika adhesives with different mechanical and deformation properties were

chosen, from a very stiff epoxy resin down to a flexible silicone. The chosen adhesives were a twocomponent epoxy resin Sikadur-30, a two component acrylate SikaFast-5211, an one component polyurethane SikaTack-Plus Booster and a two component silicon SikaSil SG-500. These adhesiveswere selected after intensive consultations with bonding experts from Sika CZ and Switzerland and passed criteria about ageing, temperature behaviour and UV stability.

Table 1-3: Overview of important properties of the additional Sika adhesives (given by the adhesives producers)

Name SikaDur 30 SikaFast 5211 SikaTack+Booster SikaSil SG500

Producer Sika Sika Sika Sika Basis EP Acrylate PU Silicone

Components 2 2 2 2Primer no no yes no

Curing time 1 days 15 min. 1,5 h 8 h

Pot time 85 min. 3 min. 5 min. 60 min.

Elongation at break 0,5% 125% 350% 100%

Colour grey beige black black

1.2 Investigation of different connection types

In this early stage it was envisaged that the cross section of the large-scale hybrid beams will possiblyconsist of steel flanges in carbon steel (S 235) and the web will be made of three laminated glass panesof toughened glass with PVB. The joints between steel flange and glass will be joined by adhesive bonding. Thus four different connection details were chosen, see Figure 1-1.


27/158

Butt spl

Figure 1-

With a v

small sc

panes o

strength

strength

the small

The bon

Butt spli

The easi

accordin

existing

and sho

redistrib

Chanel b

ChanelFurther

is slightl

but the c

Bonding

Adhesiv

of the

discreetl

on the

controlla

weatheri

surface a

Bonding

Bonding

increases

manufac

1.3 S

Experim

characte

adhesive

Figure 1

ce bonding

: Four jo

iew to simpl

le push out

toughened

and the loa

on the other

glass speci

ing geomet

e bonding:

st producin

to the colo

onding sur

s a good c

tion and the

onding in a

onding isore it can b

bigger tha

ntrollabilit

with U-prof

bonding wi

-profile. W

hide the a

adhesive vi

bility of th

g or natura

nd this way

with L-prof

with L-pro

the stiffne

ure.

all scale tes

ntal invest

istics (stren

surface and

2.

Chan

4

ning details o

ification, co

specimen w

glass. In a

carrying

side. There

en no addi

ies showed

method is

r of the ad

ace is signif

ntrollabilit

surface of t

roove:

a visual at assembled

in case of

decreases.

iles:

th U-profile

hereas a la

hesive area

scosity and

quality of

l atmospher

increase the

les:

file is alm

ss of the a

ts (push-out

igations on

th, stiffness

shear loadi

el bonding

groove

f the bonded

sts and the

ere not reali

ddition the

ehaviour o

ore and bec

ional anneal

he followin

bonding the

esive and th

icantly smal

and appear

e adhesive

ractive altein good qua

ront bondin

s turns out t

ge U-profil

especially

ranges be

application

is high. Ov

ductility be

st identical

hesive gap

tests)

small scal

, stress-strai

g in directi

25

n a Bo

onnection

bility to m

zed with la

first results

the one si

use of the p

ed glass and

strengths a

face of the

e quality of

ler than for

ance. Disad

flanks that a

native beclity with mo

g. Therefore

be more o

e appears u

y using dar

ween com

is challeng

er and abov

ause of the

as bondin

but appear

e tests wer

-relation) f

n of the ad

ding with

Profiles

asure the st

inated glas

revealed n

de and the

roblems of t

heath-stren

nd weaknes

lass-sheet

application

he other var

antageous

re exposed t

use of thedera

development of steel-glass structures-rtssd

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