Дисертації з теми "Structural Joints Testing"

In this study, ABS Publication 115, “Guidance on Fatigue Assessment of Offshore Structures” is briefly reviewed. Emphasis is on the S-N curves based fatigue assessment approach of non-tubular joints, and both size and environment effects are also considered. Further, fatigue tests are performed to study the fatigue strength of load-carrying and non-load-carrying steel cruciform joints that represent typical joint types in marine structures. The experimental results are then compared against ABS fatigue assessment methods, based on nominal stress approach, which demonstrates a need for better fatigue evaluation parameter. A good fatigue parameter by definition should be consistent and should correlate the S-N data well. The equivalent structural stress parameter is introduced to investigate the fatigue behavior of welded joints using the traction based structural stress approach on finite element models of specimens, and representing the data as a single Master S-N curve.

Adhesives have been shown to be an excellent solution for joining fibre reinforced polymer (FRP) components thanks to their capacity to redistribute loads, reduces stress concentrations and contribute to overall weight saving in the structure. The most relevant mechanical property in adhesive bonded joints design is the shear (mode II) fracture toughness of the adhesive. The application of the existing mode II delamination standards to adhesive joints entails some major limitations that result in severe under/over estimations of the adhesive properties and, in many cases, can even prevent results from being obtained from tests. The main objective of the present thesis is to develop robust tools for the determination of shear (mode II) facture toughness in adhesive joints. This includes studying data reduction methods as well as the test geometries<br>Els adhesius han demostrat ser una magnífica solució per unir components de polímers reforçats amb fibres (FRP) gràcies a la seva capacitat per redistribuir càrregues, reduir les concentracions de tensions i contribuir a l’estalvi general de pes en l’estructura. La propietat mecànica més rellevant en el disseny d’unions adhesives és la tenacitat a la fractura a tallant (mode II) de l’adhesiu. L’aplicació dels actuals assajos estandaritzats a les unions adhesives pot derivar en estimacions errònies, per sota o per sobre, de les propietats adhesives i, en molts casos, evitar que l’assaig es pugui realitzar satisfactòriament. L’objectiu principal d’aquesta tesi és el desenvolupament d’eines robustes per a la determinació de la tenacitat a la fractura a tallant (mode II) d’unions adhesives. S’estudia l’aplicabilitat dels mètodes d’assaig de deslaminació en mode II existents a les unions adhesives estructurals. Això inclou l’estudi dels mètodes de reducció de dades i de les geometries d’assaig

The objective of this thesis is to determine if the single sided resistance spot weld (RSW) can be used as a feasible connection method for cold formed steel (CFS) shear walls subject to lateral force of either seismic or wind loads on mobile shelters. The research consisted of three phases which include: a design as a 3D BIM model, connection tests of the resistance spot weld, and full-scale testing of the designed solid wall panels. The shear wall testing was conducted on specimens with both resistance spot weld and self-drilling screws and the results from tests gave a direct comparison of these connections when the solid wall panel was subjected to in-plane shear forces. The full-scale tests also included 4-point bending tests which was designed to investigate the wall panel's resistance to the lateral loads applied perpendicularly to the surface. The research discovered that the singled sided resistance spot weld achieved similar performance as the self-drilling screws in the applications of CFS wall panels for mobile shelters. The proposed single sided resistance spot weld has advantages of low cost, no added weight, fast fabrication, and it is a feasible connection method for CFS wall panels.

Bolted joints are integral parts of mechanical systems, and bolt preload loss is one of the major failure modes for bolted joint structures. Understanding the damping and frequency response to a varying preload in a single-bolted lap-joint structure can be very helpful in predicting and analyzing more complicated structures connected by these joints. In this thesis, the relationship between the bolt preload and the natural frequency, and the relationship between the bolt preload and the structural damping, have both been investigated through impact hammer testing on a single-bolted lap-joint structure. The test data revealed that the bolt preload has nonlinear effects on the structural damping and on the natural frequency of the structure. The damping ratios of the test structure were determined to increase with decreasing preload. An increase in structural damping is beneficial in most engineering circumstances, for it will reduce the vibrational response and noise subjected to external excitations. It was also observed that the modal frequency increased with increasing preload, but remained approximately constant for preload larger than 30% in the bolt yield strength. One application for studying the preload effect is the detection for loose bolts in structures. The possibility of using impact testing for estimating preload loss has been confirmed, and the modal damping was determined to be a more sensitive indicator than the natural frequency in a single-bolted lap-joint structure.

An investigation is presented into the behaviour of carbon fibre composite joints subjected to dynamic loading rates in the range of 0.1 m/s to 10 m/s. The research is focused on the response of single fastener joints and more complex structural arrangements involving multiple fasteners and complex loads. Fasteners play a crucial role in the joining of aerospace components due to their ease of installation and inspection and their resistance to creep and environmental degradation. A consequence of the operating environment of aircraft is that many critical load cases involve impact and crash. These loading events are characterised by high loading rates, high kinetic energy and possibly loads well above the static design case. The properties of composite materials change with loading rate, so it is likely that the behaviour of bolted composite joints may also vary significantly. Dynamic behaviour of bolted joints is an area of research that has been given little attention to date. The few available papers on the topic are limited to the investigation of ideal bearing loads and include some contradictory results. The research developed a detailed understanding of the behaviour of bolted joints in composite structures through a combined numerical and experimental investigation. A set of quasi-static and dynamic single fastener joint tests was conducted to develop an understanding of the complex failure mechanisms present in bolted composite joints. Simple structural tests were developed to investigate the interaction of multiple bolts in a joint. High speed camera footage, full-field strain measurement and CT scanning techniques were all used to develop an understanding of the changes in the failure process with increased loading rate. Finite element analyses used implicit and explicit dynamic algorithms to model the tests. The finite element analysis contributed to the understanding of the experimental results as well as providing a predictive tool to minimise the need for further testing. A method of incorporating detailed information about bolt failure into large scale structural models was investigated and developed. The original contributions of this thesis involve novel dynamic joint testing including dynamic pull-through and structural tests. CT Scanning was utilised in a novel way to investigate the complex failure modes within a bolted joint. Novel finite element techniques were developed for modelling bolted joints at both a detailed level and a simplified level for structural analyses. These contributions significantly improve the current understanding of bolted joint failure, both quasi-statically and dynamically, and will allow for more efficient design of bolted composite structures for crash and impact loads.

In the last few decades, there has been a shift to using more lightweight materials for the potential of fuel consumption reduction. In the Aerospace Industry, conventional metal structures are being replaced by advanced composite structures. The major advantage of an advanced composite structure is the huge reduction in the number of parts and joints required. Also composite materials provide better resistance to creep, corrosion, and fatigue. However, one cannot eliminate all the joints and attachments in an aircraft’s structure. Eliminating structural joints is impractical in present-day aircraft because of the requirements for inspection, manufacturing breaks, assembly and equipment access, and replacement of damaged structures. Currently, composite joints are overdesigned which leads to weight penalties. Understanding how to optimize the ultimate bearing strength of a composite joint by altering the cure cycle might be beneficial to the composite joint design process. This study investigates, through numerical and experimental analysis, the mechanical behavior of double shear joints. The first task is to test Aluminum double shear joint specimens inside the double shear joint fixture at a loading rate of 0.05 in./min. (quasi-static). The second task is to numerically model and validate the aluminum double shear joint specimen. The third task is to test the Unidirectional MTM 49 carbon fiber pre-preg double shear composite joint specimens with two different cure cycles and five different loading rates (0.05 in./min., 0.1 in./min., 1 in./min., 2 in./min. and 6 in./min.). The double shear composite joint specimens are made, using a heat press, with a quasi-isotropic laminate orientation of [0 0 +45 -45 +45 -45 90 90]s. The first cure cycle used is called the alternate cure cycle, which is Cytec’s MTM 49 Unidirectional Carbon Fiber pre-preg material cure cycle, and the second cure cycle used is called the datasheet cure cycle, which is Umeco's MTM 49 Unidirectional Carbon Fiber pre-preg material cure cycle. The recommended datasheet cure cycle and an alternate cure cycle are both compared to see how they affect the mechanical characteristics of the matrix along with the bearing stress. The fourth task is to adjust the Aluminum double shear joint numerical model for the double shear composite joint specimen. The numerical results for both the Aluminum and the composite specimens are in agreement with the experimental results. The theoretical in-plane material properties of the quasi-isotropic laminate were in agreement with the experimental results. One can see that at 0.05 in./min. and 0.1 in./min. (for both cure cycles) the composite double shear specimens carried more load compared to the higher loading rates of 1 in./min., 2 in./min. and 6 in./min. The tensile modulus of elasticity of an Aluminum sample is measured using a crosshead displacement, a strain gage and an extensometer. The crosshead displacement yielded very inaccurate results when compared to the strain gage and the extensometer.

The research was focused on the three major structural elements of a typical cold-formed steel building - shear wall, floor joist, and column. Part 1 of the thesis explored wider options in the steel sheet sheathing for shear walls. An experimental research was conducted on 0.030 in and 0.033 in. (2:1 and 4:1 aspect ratios) and 0.027 in. (2:1 aspect ratio) steel sheet shear walls and the results provided nominal shear strengths for the American Iron and Steel Institute Lateral Design Standard. Part 2 of this thesis optimized the web hole profile for a new generation C-joist, and the web crippling strength was analyzed by finite element analysis. The results indicated an average 43% increase of web crippling strength for the new C-joist compared to the normal C-joist without web hole. To improve the structural efficiency of a cold-formed steel column, a new generation sigma (NGS) shaped column section was developed in Part 3 of this thesis. The geometry of NGS was optimized by the elastic and inelastic analysis using finite strip and finite element analysis. The results showed an average increment in axial compression strength for a single NGS section over a C-section was 117% for a 2 ft. long section and 135% for an 8 ft. long section; and for a double NGS section over a C-section was 75% for a 2 ft. long section and 103% for an 8 ft. long section.

Since ancient times, master builders have used arches to cover large spans in masonry structures. As a consequence, nowadays the safety assessment of these structural elements plays a fundamental role in the conservation of built cultural heritage. Due to their frequent occurrence, support displacements are one of the primary sources of damage for masonry arches. Among the potential causes of support displacements, slow-moving landslides have received very little attention from the scientific community. The present thesis is motivated by the observation of extensive and severe damage in the arches of historic masonry churches exposed to slow-moving landslides. These phenomena produce a combination of vertical and horizontal supports displacements, whose effect on the arch structural behaviour has never been thoroughly investigated in the literature, especially in the framework of large displacements. In view of the above, this thesis aims at providing a full understanding of the mechanics of masonry arches subjected to large support displacements, with special attention to inclined displacements. The methodology used to accomplish this goal included both experimental tests and numerical analyses on a segmental scaled dry-joint masonry arch subjected to different combinations of horizontal and vertical support displacements. The numerical simulations were carried out in the framework of large displacements using two different numerical approaches based on finite element (FE) and rigid block (RB) modelling. A micro-modelling strategy was adopted, where the arch was modelled as an assemblage of voussoirs, very stiff and infinitely resistant in compression in the FE model and rigid in the RB model, interacting at no-tension friction interfaces. Preliminary numerical simulations, aimed at designing the experimental set-up and gaining a first insight in the arch response, were carried out considering the arch as a rigid-no tension structure. To this aim, a very large value of interface normal stiffness was adopted in the FE model. A large experimental campaign was performed on a 1:10 small-scale model built as a dry-joint assemblage of voussoirs made of a bicomponent composite material. The results of the tests allowed, for the first time in the literature, to accurately assess the effect of the direction of the imposed support displacements on the arch response in the framework of large displacements. The comparison between numerical and experimental results showed that the numerical models were not able to accurately predict the experimental response. To investigate this discrepancy, a sensitivity analysis on the effect of the interface normal stiffness on the FE predictions was performed. The results demonstrated that the difference between numerical and experimental results could be attributed due to the imperfections, and resulting deformability, of the joints of the physical model. A strategy to include imperfections in the numerical modelling, consisting in calibrating the interface normal stiffness based on the experimental results, was thus proposed and validated by performing further FE simulations, whose results were in very good agreement with the experimental evidence. Finally, to investigate the effect of geometrical imperfections on the arch response, a further experimental test was performed on a physical model made of bicomponent composite voussoirs exhibiting more imperfections. The test was simulated using a FE calibrated model to further validate the strategy proposed to model imperfections. The comparison between the experimental results for the two tested physical models showed that imperfections play a fundamental role in the response of small-scale arches to large support displacements. Furthermore, reducing the interface normal stiffness with respect to the large value adopted to model rigid interfaces proved to be an effective strategy to simulate the amount of imperfections of the experimental models.<br>Desde la antigüedad, los maestros constructores han utilizado el arco como elemento estructural para salvar grandes luces en estructuras de mampostería. En consecuencia, para la conservación del patrimonio arquitectónico es hoy en día de fundamental importancia la correcta verificación estructural de este tipo de elementos. Se ha observado frecuentemente que el desplazamiento de los apoyos es una de las principales causas de daño en arcos de mampostería. De entre las distintas causas que pueden provocar dicho desplazamiento, el deslizamiento de tierras ha recibido poca atención por parte de la comunidad científica. La presente tesis encuentra su motivación en el daño extenso y severo observado en los arcos de las iglesias de mampostería ubicadas en zonas expuestas a deslizamiento de tierras. Este fenómeno produce una combinación de desplazamientos verticales y horizontales, cuyo efecto en el comportamiento estructural de los arcos no ha sido investigado en profundidad, especialmente en lo relativo a grandes desplazamientos. Esta tesis aspira a contribuir al conocimiento del comportamiento mecánico de los arcos de mampostería sometidos a grandes desplazamientos de apoyos, con especial atención a los desplazamientos inclinados. La metodología utilitzada para dicho fin incluye ensayos experimentales y análisis numéricos en un modelo a escala de un arco de mampostería a junta seca. El modelo fue ensayado bajo diferentes combinaciones de desplazamientos horizontales y verticales en uno de sus apoyos. La simulación numérica fue desarrollada en el marco de grandes desplazamientos usando dos métodos numéricos diferentes: un modelo de elementos finitos (FE) y un modelo de bloques rígidos (RB). Los modelos fueron concebidos como un conjunto de dovelas rígidas con infinita resistencia a compresión en el modelo FE y como dovelas infinitamente rígidas en el modelo RB. En ambos modelos la interfaz entre dovelas fue modelada sin resistencia a tracción. Con el objetivo de diseñar la configuración experimental y adquirir una comprensión inicial de la respuesta del arco, se llevaron a cabo simulaciones numéricas preliminares en las cuales se consideró al arco estudiado como una estructura rígida. Para ello en el modelo FE del arco, la rigidez normal de la interfaz fue inicialmente caracterizada con un valor muy elevado. La campaña experimental fue llevada a cabo en modelos a escala 1:10. Los resultados de los ensayos experimentales permitieron, por primera vez en la literatura, un análisis preciso del efecto que tiene la dirección del desplazamiento impuesto en el comportamiento del arco en marco de grandes desplazamientos. La comparaci ón entre los resultados numéricos y experimentales mostró que los modelos numéricos no eran capaces de capturar de manera precisa la respuesta experimental. Para investigar esta discrepancia, se realizó un estudio de sensibilidad relativo al efecto de la rigidez normal de la interfaz sobre las predicciones del modelo FE. Los resultados demostraron que la diferencia entre los resultados numéricos y experimentales se debía a las imperfecciones de las juntas del modelo físico. Como consecuencia, se propuso la inclusión de imperfecciones en el modelo numérico. Para ello se calibró la rigidez normal de la interfaz según los resultados experimentales y el modelo se validó con nuevas simulaciones. Finalmente, con el fin de investigar el efecto de las imperfecciones en la respuesta del arco, se llevó a cabo otro ensayo con el mismo modelo experimental, pero añadiéndole imperfecciones. El ensayo fue simulado con un modelo calibrado FE. Los resultados obtenidos mostraron que las imperfecciones juegan un rol fundamental en la respuesta de arcos a pequeña escala con grandes desplazamientos en los apoyos. Además, la reducción de la rigidez normal de la interfaz con respecto al valor muy elevado inicialmente adoptado demostr ó ser una estrategia efectiva para simular las imperfecciones de los modelos experimentales.<br>Fin dall’antichità, i maestri costruttori hanno utilizzato gli archi per coprire grandi luci nelle strutture in muratura. Di conseguenza, ad oggi la valutazione della sicurezza di questi elementi strutturali gioca un ruolo fondamentale nella conservazione del patrimonio architettonico. A causa del loro frequente verificarsi, gli spostamenti degli appoggi sono una delle principali fonti di danno per gli archi in muratura. Tra le potenziali cause di questi spostamenti, le frane a cinematica lenta hanno ricevuto pochissima attenzione da parte della comunità scientifica. La presente tesi è motivata dall'osservazione di danni ingenti negli archi di chiese storiche in muratura interessate da frane a cinematica lenta. Questi fenomeni producono una combinazione di spostamenti verticali e orizzontali agli appoggi, il cui effetto sul comportamento strutturale dell'arco non è mai stato studiato a fondo in letteratura, soprattutto nell’ambito di grandi spostamenti. Alla luce di queste osservazioni, questa tesi si propone di fornire una piena comprensione della meccanica degli archi in muratura soggetti a grandi spostamenti degli appoggi, con particolare attenzione agli spostamenti inclinati. La metodologia utilizzata per raggiungere questo obiettivo ha incluso sia prove sperimentali che analisi numeriche su un arco ribassato in muratura di giunti a secco in piccola scala, in cui sono state applicate diverse combinazioni di spostamenti orizzontali e verticali in corrispondenza di un appoggio. Le simulazioni numeriche sono state eseguite nell’ambito dei gradi spostamenti utilizzando due diversi approcci numerici basati su una modellazione ad elementi finiti (FE) ed una modellazione a blocchi rigidi (RB). È stata adottata una strategia di micro-modellazione, in cui l'arco è stato modellato come un assemblaggio di blocchi, molto rigidi e infinitamente resistenti a compressione nel modello FE e infinitamente rigidi nel modello RB. In entrambi i modelli i blocchi erano collegati da interfacce senza resistenza a trazione. Simulazioni numeriche preliminari, finalizzate a progettare il set-up sperimentale e ad acquisire una prima conoscenza della risposta dell'arco, sono state eseguite considerando l'arco come una struttura rigida non resistente a trazione. A tal fine, nel modello FE è stato adottato un valore molto elevato di rigidezza normale delle interfacce. Un’ampia campagna sperimentale è stata eseguita su un modello in scala 1:10 costruito come un assemblaggio a secco di blocchi realizzati con un materiale composito bicomponente. I risultati delle prove sperimentali hanno permesso, per la prima volta in letteratura, di valutare con precisione l'effetto della direzione degli spostamenti imposti sulla risposta dell'arco nell’ambito dei grandi spostamenti. Il confronto tra i risultati numerici e sperimentali ha mostrato che i modelli numerici non erano in grado di cogliere in maniera accurata la risposta sperimentale, specialmente in termini di spostamento ultimo al collasso. Al fine di indagare le ragioni di questa discrepanza, è stata quindi eseguita un'analisi di sensitività relativa all’effetto della rigidezza normale delle interfacce sulle previsioni del modello FE. I risultati hanno dimostrato che la differenza tra risultati numerici e sperimentali poteva essere attribuita alle imperfezioni, e conseguente deformabilità, delle interfacce del modello fisico. Una strategia per includere le imperfezioni nella modellazione numerica, consistente nel calibrare la rigidezza normale delle interfacce sulla base dei risultati sperimentali, è stata quindi proposta e validata attraverso ulteriori simulazioni FE, i cui risultati si sono rivelati in ottimo accordo con le evidenze sperimentali. Infine, per indagare l'effetto delle imperfezioni geometriche sulla risposta dell'arco, è stata eseguita un’ulteriore prova sperimentale su un modello fisico costituito da blocchi dello stesso materiale composito bicomponente che presentavano però più imperfezioni. Al fine di validare ulteriormente la strategia proposta per modellare le imperfezioni, la prova sperimentale è stata simulata utilizzando un modello FE calibrato. Il confronto tra i risultati sperimentali per i due modelli fisici ha mostrato che le imperfezioni giocano un ruolo fondamentale nella risposta di archi in piccola scala a grandi spostamenti degli appoggi. Inoltre, ridurre la normale rigidezza dell'interfaccia rispetto al valore molto alto adottato per modellare interfacce rigide si è rivelata una strategia efficace per simulare la quantità di imperfezioni dei modelli sperimentali<br>Enginyeria de la construcció

O presente trabalho consiste basicamente num estudo experimental de juntas híbridas metal-compósito unidas mecanicamente por fixadores. Foram analisadas juntas fabricadas através de uma chapa metálica de titânio unida a uma placa em compósito de fibra de carbono e resina epóxi por fixadores de monel. As juntas avaliadas são juntas simples (\"single lap joint\"), ou seja, as mesmas foram submetidas ao simples cisalhamento. Antes, porém, dos ensaios das juntas, foram fabricados corpos-de-prova (CDPs) do compósito seguindo as especificações das normas ASTM D3039 e ASTM D3518. Os ensaios de tração e cisalhamento dos CDPs de compósito possibilitaram a determinação de propriedades mecânicas, bem como de valores de resistência. Sob posse das propriedades e resistência média, foram executadas simulações computacionais via Método dos Elementos Finitos com o intuito de prever o comportamento mecânico das juntas a serem ensaiadas seguindo a norma ASTM D5961 e, assim, delinear estratégias para os ensaios. Os ensaios das juntas foram realizados, possibilitando assim a avaliação do comportamento mecânico de juntas híbridas e de seus mecanismos de falha. Por fim, as conclusões e as perspectivas para trabalhos futuros foram apresentadas.<br>This work consists on an experimental investigation of hybrid joints (metal-composite) joined by fasteners. For this work, hybrid joints of titanium joined to composite (carbon fiber with epoxy resin) by monel fasteners were manufactured. Only single lap joints were investigated. However, before manufacturing specimens of joints, composite specimens were tested following the ASTM D3039 e ASTM D3518. The tensile and shear tests provided the mechanical properties and strength values of the composite. Finite element analyses of the hybrid joints were carried out, using average mechanical properties and strength values. These simulations followed the specifications of ASTM D5961 in order to predict the mechanical behavior of the joints during the experimental tests, as well as, provide a good strategy for the test setup. The experimental tests were carried out, observing the mechanical behavior and failure mechanisms of the hybrid joints. Finally, the conclusions and perspective of future works were showed.

Fires following earthquake (FFE) have historically produced enormous post-earthquake damage and losses in terms of lives, buildings and economic costs, like the San Francisco earthquake (1906), the Kobe earthquake (1995), the Turkey earthquake (2011), the Tohoku earthquake (2011) and the Christchurch earthquakes (2011). The structural fire performance can worsen significantly because the fire acts on a structure damaged by the seismic event. On these premises, the purpose of this work is the investigation of the experimental and numerical response of structural and non-structural components of steel structures subjected to fire following earthquake (FFE) to increase the knowledge and provide a robust framework for hybrid fire testing and hybrid fire following earthquake testing. A partitioned algorithm to test a real case study with substructuring techniques was developed. The framework is developed in MATLAB and it is also based on the implementation of nonlinear finite elements to model the effects of earthquake forces and post-earthquake effects such as fire and thermal loads on structures. These elements should be able to capture geometrical and mechanical non-linearities to deal with large displacements. Two numerical validation procedures of the partitioned algorithm simulating two virtual hybrid fire testing and one virtual hybrid seismic testing were carried out. Two sets of experimental tests in two different laboratories were performed to provide valuable data for the calibration and comparison of numerical finite element case studies reproducing the conditions used in the tests. Another goal of this thesis is to develop a fire following earthquake numerical framework based on a modified version of the OpenSees software and several scripts developed in MATLAB to perform probabilistic analyses of structures subjected to FFE. A new material class, namely SteelFFEThermal, was implemented to simulate the steel behaviour subjected to FFE events.

The objective of this research is to develop a method to evaluate important weld dimensions in thin plates by using laser generated ultrasounds and EMAT receiver. The superimposed laser sources (SLS) technique is developed to generate narrowband Lamb waves with fixed wavelengths in thin plates. The method permits the flexibility of selecting desired wavelength. The signal processing procedure that combines wavenumber-frequency (k-w) domain filtering and synthetic phase tuning (SPT) is used to further reduce the complexity of Lamb waves. The k-w domain filtering technique helps to filter out the unwanted wave components traveling at the direction that is not of interest to us and the SPT technique is applied to amplify and isolate a particular Lamb wave mode. The signal processing procedure facilitates the calculation of reflection coefficients of Lamb waves that result from the presence of weld joints. The SLS and signal processing procedure are then applied to measure reflection coefficients in butt welds and lap welds. Two methods, the direct method and indirect method, are used to develop models that use reflection coefficients as predictors to predict these weld dimensions. The models developed in this research are shown to accurately predict weld dimensions in thin plates.

This thesis deals with the exploration and evaluation of the existing bridge carried him on the highway D2. The work is divided into theoretical and practical parts. The theoretical part focuses on the technical surveys, diagnosis of building structures and some methods of investigation and testing of building structures. In the practical part the visual inspection and diagnosis of disorders of the highway bridge substructures ev. No. D2-058, to determine material characteristics substructure and evaluate the state of the bridge. In conclusion, the practical part of the recommendations for the design and method of repairing the bridge.

Bestärkt durch das gesellschaftliche und wirtschaftliche Interesse an nachhaltigen und ressourcenschonenden Formen des Bauens gewinnen Holzkonstruktionen wieder unverkennbar an Bedeutung. Mit dieser Entwicklung bilden sich neue Konstruktionsprinzipien und Materialkombinationen im Bauwesen heraus, zu deren ingenieurtechnischer Beurteilung zum Teil keine ausreichenden Erkenntnisse vorliegen. Verbundkonstruktionen aus Holz und Glas sind eine innovative Bauweise, die zu einer höheren Materialeffizienz in Fassaden beiträgt, deren Wirkungsweise aber noch nicht ausreichend hinterfragt wurde. Werden Holz und Glas durch eine tragende Klebung verbunden, lässt sich das vielfach ungenutzte Tragpotenzial ausschöpfen, das eine in Scheibenebene belastete Verglasung aufweist. Die Qualität der Klebung entscheidet dabei über die Eigenschaften und das Leistungsvermögen des Bauteils. Die üblicherweise an dieser Schnittstelle eingesetzten Silikonklebstoffe weisen eine hohe Nachgiebigkeit und eine vergleichsweise geringe Festigkeit auf. Wenn die Verbundelemente als Aussteifung mitwirken sollen, bleibt ihr Einsatz deswegen auf Gebäude mit höchstens zwei Geschossen limitiert. Die vorliegende Arbeit trägt entscheidend zur Erweiterung der baulichen Möglichkeiten bei, indem sie der Anwendbarkeit von hochfesten Klebstoffen, die für den Einsatz im Bauwesen nur wenig erforscht sind, auf vielschichtige Weise nachgeht. Im Fokus stehen aussteifende Holz-Glas-Verbundelemente für die Fassade. Weder die Bauart noch das Bauprodukt Klebstoff sind derzeit in Deutschland in einer Norm erfasst. Das Klären der baurechtlichen Rahmenbedingungen ist daher unerlässlich und erfolgt mit engem Bezug zum konstruktiven Glasbau. Zusätzlich zur wissenschaftlichen Interpretation wird dadurch eine praxisnahe Bewertung der Versuchsergebnisse möglich, was ein Alleinstellungsmerkmal dieser Arbeit darstellt. Das Verformungsvermögen des Klebstoffs spielt eine zentrale Rolle bei der Materialauswahl und Gestaltung der Holz-Glas-Verbundelemente. Der Einfluss der Klebstoffsteifigkeit auf das Tragverhalten eines Einzelelements und auf dessen Interaktion mit den anderen Bestandteilen des Tragwerks wird an einem Modellgebäude untersucht. Auf Basis dieser Parameterstudie lassen sich drei Steifigkeitsbereiche definieren, auf die sich die Klebstoffauswahl für die weiteren Untersuchungen stützt. Der experimentelle Teil der Arbeit beginnt mit der ausführlichen Charakterisierung von sieben Klebstoffen. Davon werden zwei höherfeste Klebstoffe als geeignet identifiziert. Ein Silikonklebstoff wird als Referenzmaterial zur aktuellen Anwendungspraxis festgelegt. Das Hauptaugenmerk der folgenden Experimente richtet sich auf Aspekte der Alterungsbeständigkeit und des zeitabhängigen Materialverhaltens unter langandauernder mechanischer Beanspruchung. In labormaßstäblichen Alterungsprüfungen werden die Klebstoffproben unterschiedlichen Schadeinwirkungen ausgesetzt, die im Glas- und Fassadenbau relevant sind. Darüber hinaus erfolgen Kriechversuche an kleinen und großen Scherprüfkörpern. Letztere stellen einen besonderen Mehrwert dar, da sie eine realistische Klebfugengeometrie aufweisen und die Ergebnisse dadurch dem tatsächlichen Bauteilverhalten nahekommen. Für diese Zeitstandversuche wurde eine bislang einzigartige Versuchsanlage aus sechs Prüfrahmen mit Gasdruckfederbelastung entwickelt. Im Ergebnis zeigt sich, dass mit den gewählten höherfesten Klebstoffen die Festigkeit der nicht gealterten Klebschichten erwartungsgemäß gesteigert werden kann. Der Bruch des Fügepartners Holz wird zum maßgebenden Versagenskriterium. Die Verformungen des Verbundelements reduzieren sich gegenüber einer Silikonklebung deutlich. Allerdings offenbaren sich in einzelnen Alterungsszenarien und unter langandauernder Belastung auch Schwachstellen dieser Klebstoffe. Ihre Verwendung kann daher nur mit konstruktiven Kompensationsmaßnahmen oder durch Abschirmen der kritischen Einwirkungsgrößen empfohlen werden. Entsprechende Vorschläge werden bei der abschließenden Bewertung der Ergebnisse unterbreitet. Verfahren und Beurteilungsmethoden, die in dieser Arbeit angewendet und entwickelt werden, erleichtern die zukünftige Bewertung weiterer aussichtsreicher Klebstoffe für den Holz-Glas-Verbund<br>Wooden constructions are on the rise again – encouraged by a strong public and economic trend towards sustainable and resource efficient buildings. Spurred by this growing interest novel design principles and material assemblies in architecture and the building industry evolve. These developments require further research due to the absence of evaluation tools and insufficient knowledge about their design. Load-bearing timber-glass composite elements could contribute to a more efficient use of materials in façade constructions. In this case a linear adhesive bond connects the glass pane to the timber substructure. This enables an in-plane loading of the glass whose capacity is not used to its full potential in conventional façades as it is solely applied as an infill panel. The quality of the adhesive bond defines the characteristics and the performance of the whole structural component. Structural sealants such as silicones, which are typically used for the joint, provide a high flexibility and only a low load-bearing capacity. Considering such elements being part of a bracing system, the mentioned characteristics limit the application range to buildings with not more than two stories. This thesis widens the scope with an in-depth examination of high-modulus adhesives, which have not yet been evaluated for their use in building constructions. Timber-glass composite elements used as a bracing component in façades are the focus of this work. Neither the full structural component nor the adhesive have yet been included into German building standards. Hence it is essential to assess the general requirements of their application. The relevant aspects are clarified in the context of glass constructions. In addition to the scientific discussion of the results, this approach facilitates also a practical evaluation of the findings, which is a unique feature of this work. The deformability of the adhesive becomes a crucial criterion when selecting the individual materials and designing the timber-glass composite elements. A case study assesses the influence of the adhesive stiffness on the behavior of a single element and its interaction with other members of the structural system. Based on the results, three different stiffness classes are introduced to support the selection process of the adhesives to be examined in further investigations. The experimental part of this work is initiated by a comprehensive characterization of seven shortlisted adhesives. The results enable a further differentiation of suitable materials. Two adhesives qualified as suitable for the main experiments. A silicone adhesive complements the test series to serve as a reference material to the current practice. In the next phase attention is drawn to the ageing stability and on the time-dependent material behavior of the adhesives under long-term loading. Small-scale specimens made from adhesively joint timber and glass pieces are exposed to different ageing scenarios which relate to the impacts typically encountered in façades. Beyond that, creep tests are carried out on small and large shear specimen. The latter provide extra benefit as they comprise long linear adhesive joints resembling virtually the situation in a real-size element. A specific long-term test rig was developed for this purpose comprising a loading unit with gas pressurized springs. Based on the results it can be concluded that joints with adhesives of high and intermediate stiffness enable an increase of characteristic failure loads and a significant reduction of deformation. With the stiffer joint near-surface rupture of timber fibers becomes the prevailing failure mechanism. The timber strength limits further loading of the adhesive joint. However, ageing and creep testing reveal also shortcomings of the adhesives. Their application can only be recommended if redundant compensation measures are taken or the joint is protected against critical environmental impacts. Appropriate solutions are proposed with the final recommendations of this work. Methods and assessment tools that have been developed and tested for this work offer the possibility of a more straight-forward evaluation of further promising adhesives and their use in load-bearing timber-glass composites

The inclusion of trapezoidal types of steel decking in the shear connection of composite beams has been found to significantly reduce their maximum strength and ductility by causing premature concrete-related failure modes. In order to investigate the complex behaviour and various load-transfer mechanisms that can occur in composite beams incorporating this type of connections, a total of 91 carefully-designed push-out tests were performed. Specific failure modes in conventionally reinforced specimens were initially induced by varying critical parameters. Specimens incorporating specific stud reinforcing devices were subsequently tested to suppress the undesirable failure modes. The concrete reinforcing and stud performance-enhancing devices, which included novel waveform-type reinforcement elements and spiral wire or ring components surrounding individual studs in secondary composite beams and special haunch reinforcement in primary beam applications, significantly delayed the onset and reduced the effect of the premature concrete-related failure modes. Hence, they increased the ultimate strength and ductility of the shear connection. The findings of the small-scale push-out tests were also verified in two full-scale composite beam tests which showed good agreement in shear connection behaviour and failure mode. Most of the design approaches currently used around the world take into account the weakening effect of trapezoidal types of decking by applying a reduction factor to the nominal strength that the same connection would have in a solid slab. From the test results, it is evident that not every shear connection incorporating steel decking, and within the limits of the associated standards, can be classified as ductile. A new and more reliable design approach is proposed which also incorporates the application of the various stud reinforcing devices. The key element of this design approach is to classify the anticipated connection behaviour, in regards to its deformation capacity, into ductile or brittle connections, hence ensuring satisfactory shear connection behaviour where the new types of trapezoidal steel decking are used. A reliability analysis of the new proposal is presented which enables the application of this new approach in accordance with AS 2327.1 (Standards Australia 2003). It is calibrated to provide a reliability index similar to stud applications currently in use. Simple strength reduction factors for the types of trapezoidal steel decking available in Australia are also provided which can be applied to the current solid slab shear connection strength for a fast and simplified design.<br>Doctor of Philosophy (PhD)

"1st February 2002"<br>Includes bibliographical references (leaves 265-273)<br>xi, 273 leaves : ill. (some col.), plates (col.) ; 30 cm.<br>Title page, contents and abstract only. The complete thesis in print form is available from the University Library.<br>Concerns the specialized requirements of welding procedures used on operational gas pipelines.<br>Thesis (Ph.D.)--University of Adelaide, Dept. of Mechanical Engineering, 2004?

"1st February 2002"<br>Includes bibliographical references (leaves 265-273)<br>xi, 273 leaves : ill. (some col.), plates (col.) ; 30 cm.<br>Concerns the specialized requirements of welding procedures used on operational gas pipelines.<br>Thesis (Ph.D.)--University of Adelaide, Dept. of Mechanical Engineering, 2004?

Copies of author's previously published articles inserted.<br>Bibliography: leaves 254-264.<br>xx, 297, [26] leaves : ill. ; 30 cm.<br>Studies the effects of various weld geometry parameters, residual stresses and the combined axial and bending loadings on the fatigue behaviour of butt-welded steel joints. Presents ways of improving the fatigue strength. Simulates the effect of the induced surface compressive residual stresses on the welded joints (for the improvement of the fatigue life). Explains the phenomenon of large scatter band associated with fatigue tests results. Suggests a new procedure for performing and evaluating the fatigue tests.<br>Thesis (Ph.D.)--University of Adelaide, Dept. of Mechanical Engineering, 1996

Bestärkt durch das gesellschaftliche und wirtschaftliche Interesse an nachhaltigen und ressourcenschonenden Formen des Bauens gewinnen Holzkonstruktionen wieder unverkennbar an Bedeutung. Mit dieser Entwicklung bilden sich neue Konstruktionsprinzipien und Materialkombinationen im Bauwesen heraus, zu deren ingenieurtechnischer Beurteilung zum Teil keine ausreichenden Erkenntnisse vorliegen. Verbundkonstruktionen aus Holz und Glas sind eine innovative Bauweise, die zu einer höheren Materialeffizienz in Fassaden beiträgt, deren Wirkungsweise aber noch nicht ausreichend hinterfragt wurde. Werden Holz und Glas durch eine tragende Klebung verbunden, lässt sich das vielfach ungenutzte Tragpotenzial ausschöpfen, das eine in Scheibenebene belastete Verglasung aufweist. Die Qualität der Klebung entscheidet dabei über die Eigenschaften und das Leistungsvermögen des Bauteils. Die üblicherweise an dieser Schnittstelle eingesetzten Silikonklebstoffe weisen eine hohe Nachgiebigkeit und eine vergleichsweise geringe Festigkeit auf. Wenn die Verbundelemente als Aussteifung mitwirken sollen, bleibt ihr Einsatz deswegen auf Gebäude mit höchstens zwei Geschossen limitiert. Die vorliegende Arbeit trägt entscheidend zur Erweiterung der baulichen Möglichkeiten bei, indem sie der Anwendbarkeit von hochfesten Klebstoffen, die für den Einsatz im Bauwesen nur wenig erforscht sind, auf vielschichtige Weise nachgeht. Im Fokus stehen aussteifende Holz-Glas-Verbundelemente für die Fassade. Weder die Bauart noch das Bauprodukt Klebstoff sind derzeit in Deutschland in einer Norm erfasst. Das Klären der baurechtlichen Rahmenbedingungen ist daher unerlässlich und erfolgt mit engem Bezug zum konstruktiven Glasbau. Zusätzlich zur wissenschaftlichen Interpretation wird dadurch eine praxisnahe Bewertung der Versuchsergebnisse möglich, was ein Alleinstellungsmerkmal dieser Arbeit darstellt. Das Verformungsvermögen des Klebstoffs spielt eine zentrale Rolle bei der Materialauswahl und Gestaltung der Holz-Glas-Verbundelemente. Der Einfluss der Klebstoffsteifigkeit auf das Tragverhalten eines Einzelelements und auf dessen Interaktion mit den anderen Bestandteilen des Tragwerks wird an einem Modellgebäude untersucht. Auf Basis dieser Parameterstudie lassen sich drei Steifigkeitsbereiche definieren, auf die sich die Klebstoffauswahl für die weiteren Untersuchungen stützt. Der experimentelle Teil der Arbeit beginnt mit der ausführlichen Charakterisierung von sieben Klebstoffen. Davon werden zwei höherfeste Klebstoffe als geeignet identifiziert. Ein Silikonklebstoff wird als Referenzmaterial zur aktuellen Anwendungspraxis festgelegt. Das Hauptaugenmerk der folgenden Experimente richtet sich auf Aspekte der Alterungsbeständigkeit und des zeitabhängigen Materialverhaltens unter langandauernder mechanischer Beanspruchung. In labormaßstäblichen Alterungsprüfungen werden die Klebstoffproben unterschiedlichen Schadeinwirkungen ausgesetzt, die im Glas- und Fassadenbau relevant sind. Darüber hinaus erfolgen Kriechversuche an kleinen und großen Scherprüfkörpern. Letztere stellen einen besonderen Mehrwert dar, da sie eine realistische Klebfugengeometrie aufweisen und die Ergebnisse dadurch dem tatsächlichen Bauteilverhalten nahekommen. Für diese Zeitstandversuche wurde eine bislang einzigartige Versuchsanlage aus sechs Prüfrahmen mit Gasdruckfederbelastung entwickelt. Im Ergebnis zeigt sich, dass mit den gewählten höherfesten Klebstoffen die Festigkeit der nicht gealterten Klebschichten erwartungsgemäß gesteigert werden kann. Der Bruch des Fügepartners Holz wird zum maßgebenden Versagenskriterium. Die Verformungen des Verbundelements reduzieren sich gegenüber einer Silikonklebung deutlich. Allerdings offenbaren sich in einzelnen Alterungsszenarien und unter langandauernder Belastung auch Schwachstellen dieser Klebstoffe. Ihre Verwendung kann daher nur mit konstruktiven Kompensationsmaßnahmen oder durch Abschirmen der kritischen Einwirkungsgrößen empfohlen werden. Entsprechende Vorschläge werden bei der abschließenden Bewertung der Ergebnisse unterbreitet. Verfahren und Beurteilungsmethoden, die in dieser Arbeit angewendet und entwickelt werden, erleichtern die zukünftige Bewertung weiterer aussichtsreicher Klebstoffe für den Holz-Glas-Verbund.:1 Einleitung 13 1.1 Motivation 13 1.2 Zielsetzung 18 1.3 Abgrenzung 20 1.4 Vorgehensweise 21 2 Die Holz-Glas-Verbundbauweise 25 2.1 Tragprinzip und Wirkungsweise 25 2.2 Forschungsschwerpunkte und Anwendungen 27 2.2.1 Geklebte Verglasungssysteme für Fenster 27 2.2.2 Träger 28 2.2.3 Wandscheiben und Schubfelder 32 2.2.4 Verbundplatten 36 2.3 Tragendes Glas im Verbund 37 2.3.1 Relevanz für Holz-Glas-Verbundlösungen 37 2.3.2 Historische Vorbilder 37 2.3.3 Verbundglas und Verbund-Sicherheitsglas 38 2.3.4 Verbundträger 40 2.3.5 Wandscheiben aus Glas 43 2.4 Konstruktionsprinzipien von tragenden Wand und Fassadenelementen aus Holz und Glas 46 2.4.1 Aufbau 46 2.4.2 Verglasung 46 2.4.3 Ausbildung der Klebfuge 48 2.4.4 Marktreife Systeme mit Koppelleiste 49 2.4.5 Identifizieren geeigneter Tragsysteme 52 2.4.6 Skelett-, Tafel- und Massivholzbauweise 53 2.5 Zusammenfassung wesentlicher Erkenntnisse 55 3 Klebverbindungen im Glasbau 57 3.1 Fügen von Glas 57 3.1.1 Besondere Merkmale des Fügewerkstoffs 57 3.1.2 Wirkprinzip und Fügeverfahren 60 3.1.3 Vor- und Nachteile von Klebverbindungen 61 3.1.4 Glasoberfläche 65 3.2 Typische Anwendungsbeispiele im Glasbau 67 3.2.1 Klassifizierung 67 3.2.2 Einordung der Holz-Glas-Verbundbauweise 69 3.2.3 Structural Sealant Glazing 71 3.2.4 Ganzglaskonstruktionen 74 3.3 Planungsstrategien 76 3.3.1 Sicheres Bauteilversagen 76 3.3.2 Redundanz und Versagensszenarien 78 3.3.3 Besonderheiten bei geklebten Verglasungen 80 3.4 Baurechtliche Rahmenbedingungen 82 3.4.1 Normung und Verfahrensweise in Deutschland 82 3.4.2 Harmonisierung auf europäischer Ebene 84 3.4.3 ETAG 002 – Leitlinie für Structural Glazing 86 3.4.4 Der Weg zur geklebten Glaskonstruktion 88 4 Einfluss der Klebstoffsteifigkeit auf aussteifende Holz-Glas-Verbundtragwerke 91 4.1 Aussteifung von Holzbauten 91 4.2 Berechnungsverfahren 92 4.2.1 Begründung der Auswahl der Verfahren 92 4.2.2 Verteilung von Horizontallasten auf die Wandscheiben eines Aussteifungssystems 93 4.2.3 Wandscheibe als Schubfeld 95 4.2.4 Federmodelle 97 4.3 Randbedingungen für die Analyse 101 4.3.1 Modellgebäude 101 4.3.2 Konstruktive Gestaltung 103 4.3.3 Lastannahmen 104 4.4 Parameterstudie 107 4.4.1 Nachgiebigkeit der Kernwände 107 4.4.2 Nachgiebigkeit eines Verbundelements 108 4.4.3 Auswirkung der Elementanordnung 112 4.4.4 Lastumlagerung bei Ausfall von Elementen 114 4.4.5 Horizontallastanteil auf Fassade und Kern 116 4.5 Rückschlüsse auf die Tragsystemgestaltung und die Klebstoffauswahl 120 5 Materialauswahl und -charakterisierung 123 5.1 Untersuchungsprogramm 123 5.2 Materialeigenschaften der Fügeteile 124 5.2.1 Glas 124 5.2.2 Holz und Holzwerkstoffe 126 5.3 Klebstoffe 128 5.3.1 Auswahlkriterien für Holz-Glas-Klebungen 128 5.3.2 Vorauswahl der Klebstoffsysteme 130 5.4 Experimentelle Methoden zur Charakterisierung der Klebstoffe 134 5.4.1 Dynamisch-mechanische Analyse 134 5.4.2 Einaxialer Zugversuch 135 5.4.3 Scherversuch 138 5.5 Versuchsergebnisse 141 5.5.1 Glasübergangstemperatur 141 5.5.2 Spannungs-Dehnungs-Beziehung 145 5.5.3 Einpunktkennwerte 150 5.5.4 Scherfestigkeit und Bruchbildanalyse 151 5.6 Klebstoffauswahl für die Hauptuntersuchungen 155 6 Experimentelle Untersuchungen an Klebverbindungen im Labormaßstab 157 6.1 Methodik 157 6.1.1 Untersuchungsgegenstand 157 6.1.2 Beurteilungsgrundlagen 158 6.1.3 Untersuchungsprogramm 159 6.1.4 Auswertungsmethoden 162 6.2 Geometrie und Herstellung der Prüfkörper 164 6.2.1 Prüfkörper zum Bestimmen der Haftfestigkeit vor und nach künstlicher Alterung 164 6.2.2 Scherprüfkörper für Kriechversuche 165 6.2.3 Vorbereiten und Konditionieren der Proben 166 6.3 Verfahren zur mechanischen Prüfung und zur künstlichen Alterung 168 6.3.1 Zug- und Scherversuche 168 6.3.2 Lagerung unter UV-Bestrahlung 170 6.3.3 Lagerung in Reinigungsmittellösung 171 6.3.4 Holzfeuchtewechsel bei +20 °C 172 6.3.5 Lagerung in schwefeldioxidhaltiger Atmosphäre 173 6.3.6 Kriechversuche 174 6.4 Auswertung der Versuchsergebnisse 176 6.4.1 Anfangsfestigkeit im Scherversuch 176 6.4.2 Anfangsfestigkeit im Zugversuch 181 6.4.3 Sichtbare Veränderungen der Klebschicht 183 6.4.4 Restfestigkeit nach Alterung 185 6.4.5 Analyse der Versagensmuster 189 6.4.6 Kriechverhalten 192 6.4.7 Restfestigkeit nach Vorbelastung 198 7 Experimentelle Untersuchungen an bauteilähnlichen Prüfkörpern 201 7.1 Untersuchungsprogramm und Methodik 201 7.1.1 Ziel der Untersuchungen 201 7.1.2 Materialien 202 7.1.3 Großer Scherprüfkörper 203 7.1.4 Herstellung der Prüfkörper 205 7.1.5 Versuchsprogramm – Bauteilversuche 207 7.2 Entwicklung eines Kriechprüfstands 210 7.2.1 Prüfrahmen 210 7.2.2 Lasteinleitung 211 7.2.3 Belastungsvorgang 212 7.2.4 Messtechnik und Monitoring 213 7.2.5 Modifikation für Kurzzeitversuche 214 7.3 Große Scherversuche unter Kurz- und Langzeiteinwirkung 215 7.3.1 Tragfähigkeit bei kurzzeitiger Lasteinwirkung 215 7.3.2 Spannungsverteilung im Glas 219 7.3.3 Kriechversuche mit 1000 Stunden Laufzeit 221 7.3.4 Verlängerte Kriechversuche am Klebstoff mit mittlerer Steifigkeit 226 7.3.5 Tragfähigkeit nach Vorbelastung 230 8 Bewertung und Handlungsempfehlung 231 8.1 Alterungsverhalten 231 8.2 Korrelation der Ergebnisse aus Fügeteil- und 233 Bauteilversuchen 8.2.1 Versuche bei kurzzeitiger Lasteinwirkung 233 8.2.2 Versuche bei langandauernder Lasteinwirkung 235 8.3 Der Vorzugsklebstoff und seine Einsatzgrenzen 238 8.4 Konstruktion 241 9 Zusammenfassung und Ausblick 243 9.1 Zusammenfassung 243 9.2 Ausblick 249 10 Literatur 253 11 Abbildungsverzeichnis 263 12 Tabellenverzeichnis 267 13 Bezeichnungen 268 Anhang A Materialkennwerte zur Klebstoffauswahl 271 B Klebverbindungen im Labormaßstab 287 C Bauteilähnliche Prüfkörper 373<br>Wooden constructions are on the rise again – encouraged by a strong public and economic trend towards sustainable and resource efficient buildings. Spurred by this growing interest novel design principles and material assemblies in architecture and the building industry evolve. These developments require further research due to the absence of evaluation tools and insufficient knowledge about their design. Load-bearing timber-glass composite elements could contribute to a more efficient use of materials in façade constructions. In this case a linear adhesive bond connects the glass pane to the timber substructure. This enables an in-plane loading of the glass whose capacity is not used to its full potential in conventional façades as it is solely applied as an infill panel. The quality of the adhesive bond defines the characteristics and the performance of the whole structural component. Structural sealants such as silicones, which are typically used for the joint, provide a high flexibility and only a low load-bearing capacity. Considering such elements being part of a bracing system, the mentioned characteristics limit the application range to buildings with not more than two stories. This thesis widens the scope with an in-depth examination of high-modulus adhesives, which have not yet been evaluated for their use in building constructions. Timber-glass composite elements used as a bracing component in façades are the focus of this work. Neither the full structural component nor the adhesive have yet been included into German building standards. Hence it is essential to assess the general requirements of their application. The relevant aspects are clarified in the context of glass constructions. In addition to the scientific discussion of the results, this approach facilitates also a practical evaluation of the findings, which is a unique feature of this work. The deformability of the adhesive becomes a crucial criterion when selecting the individual materials and designing the timber-glass composite elements. A case study assesses the influence of the adhesive stiffness on the behavior of a single element and its interaction with other members of the structural system. Based on the results, three different stiffness classes are introduced to support the selection process of the adhesives to be examined in further investigations. The experimental part of this work is initiated by a comprehensive characterization of seven shortlisted adhesives. The results enable a further differentiation of suitable materials. Two adhesives qualified as suitable for the main experiments. A silicone adhesive complements the test series to serve as a reference material to the current practice. In the next phase attention is drawn to the ageing stability and on the time-dependent material behavior of the adhesives under long-term loading. Small-scale specimens made from adhesively joint timber and glass pieces are exposed to different ageing scenarios which relate to the impacts typically encountered in façades. Beyond that, creep tests are carried out on small and large shear specimen. The latter provide extra benefit as they comprise long linear adhesive joints resembling virtually the situation in a real-size element. A specific long-term test rig was developed for this purpose comprising a loading unit with gas pressurized springs. Based on the results it can be concluded that joints with adhesives of high and intermediate stiffness enable an increase of characteristic failure loads and a significant reduction of deformation. With the stiffer joint near-surface rupture of timber fibers becomes the prevailing failure mechanism. The timber strength limits further loading of the adhesive joint. However, ageing and creep testing reveal also shortcomings of the adhesives. Their application can only be recommended if redundant compensation measures are taken or the joint is protected against critical environmental impacts. Appropriate solutions are proposed with the final recommendations of this work. Methods and assessment tools that have been developed and tested for this work offer the possibility of a more straight-forward evaluation of further promising adhesives and their use in load-bearing timber-glass composites.:1 Einleitung 13 1.1 Motivation 13 1.2 Zielsetzung 18 1.3 Abgrenzung 20 1.4 Vorgehensweise 21 2 Die Holz-Glas-Verbundbauweise 25 2.1 Tragprinzip und Wirkungsweise 25 2.2 Forschungsschwerpunkte und Anwendungen 27 2.2.1 Geklebte Verglasungssysteme für Fenster 27 2.2.2 Träger 28 2.2.3 Wandscheiben und Schubfelder 32 2.2.4 Verbundplatten 36 2.3 Tragendes Glas im Verbund 37 2.3.1 Relevanz für Holz-Glas-Verbundlösungen 37 2.3.2 Historische Vorbilder 37 2.3.3 Verbundglas und Verbund-Sicherheitsglas 38 2.3.4 Verbundträger 40 2.3.5 Wandscheiben aus Glas 43 2.4 Konstruktionsprinzipien von tragenden Wand und Fassadenelementen aus Holz und Glas 46 2.4.1 Aufbau 46 2.4.2 Verglasung 46 2.4.3 Ausbildung der Klebfuge 48 2.4.4 Marktreife Systeme mit Koppelleiste 49 2.4.5 Identifizieren geeigneter Tragsysteme 52 2.4.6 Skelett-, Tafel- und Massivholzbauweise 53 2.5 Zusammenfassung wesentlicher Erkenntnisse 55 3 Klebverbindungen im Glasbau 57 3.1 Fügen von Glas 57 3.1.1 Besondere Merkmale des Fügewerkstoffs 57 3.1.2 Wirkprinzip und Fügeverfahren 60 3.1.3 Vor- und Nachteile von Klebverbindungen 61 3.1.4 Glasoberfläche 65 3.2 Typische Anwendungsbeispiele im Glasbau 67 3.2.1 Klassifizierung 67 3.2.2 Einordung der Holz-Glas-Verbundbauweise 69 3.2.3 Structural Sealant Glazing 71 3.2.4 Ganzglaskonstruktionen 74 3.3 Planungsstrategien 76 3.3.1 Sicheres Bauteilversagen 76 3.3.2 Redundanz und Versagensszenarien 78 3.3.3 Besonderheiten bei geklebten Verglasungen 80 3.4 Baurechtliche Rahmenbedingungen 82 3.4.1 Normung und Verfahrensweise in Deutschland 82 3.4.2 Harmonisierung auf europäischer Ebene 84 3.4.3 ETAG 002 – Leitlinie für Structural Glazing 86 3.4.4 Der Weg zur geklebten Glaskonstruktion 88 4 Einfluss der Klebstoffsteifigkeit auf aussteifende Holz-Glas-Verbundtragwerke 91 4.1 Aussteifung von Holzbauten 91 4.2 Berechnungsverfahren 92 4.2.1 Begründung der Auswahl der Verfahren 92 4.2.2 Verteilung von Horizontallasten auf die Wandscheiben eines Aussteifungssystems 93 4.2.3 Wandscheibe als Schubfeld 95 4.2.4 Federmodelle 97 4.3 Randbedingungen für die Analyse 101 4.3.1 Modellgebäude 101 4.3.2 Konstruktive Gestaltung 103 4.3.3 Lastannahmen 104 4.4 Parameterstudie 107 4.4.1 Nachgiebigkeit der Kernwände 107 4.4.2 Nachgiebigkeit eines Verbundelements 108 4.4.3 Auswirkung der Elementanordnung 112 4.4.4 Lastumlagerung bei Ausfall von Elementen 114 4.4.5 Horizontallastanteil auf Fassade und Kern 116 4.5 Rückschlüsse auf die Tragsystemgestaltung und die Klebstoffauswahl 120 5 Materialauswahl und -charakterisierung 123 5.1 Untersuchungsprogramm 123 5.2 Materialeigenschaften der Fügeteile 124 5.2.1 Glas 124 5.2.2 Holz und Holzwerkstoffe 126 5.3 Klebstoffe 128 5.3.1 Auswahlkriterien für Holz-Glas-Klebungen 128 5.3.2 Vorauswahl der Klebstoffsysteme 130 5.4 Experimentelle Methoden zur Charakterisierung der Klebstoffe 134 5.4.1 Dynamisch-mechanische Analyse 134 5.4.2 Einaxialer Zugversuch 135 5.4.3 Scherversuch 138 5.5 Versuchsergebnisse 141 5.5.1 Glasübergangstemperatur 141 5.5.2 Spannungs-Dehnungs-Beziehung 145 5.5.3 Einpunktkennwerte 150 5.5.4 Scherfestigkeit und Bruchbildanalyse 151 5.6 Klebstoffauswahl für die Hauptuntersuchungen 155 6 Experimentelle Untersuchungen an Klebverbindungen im Labormaßstab 157 6.1 Methodik 157 6.1.1 Untersuchungsgegenstand 157 6.1.2 Beurteilungsgrundlagen 158 6.1.3 Untersuchungsprogramm 159 6.1.4 Auswertungsmethoden 162 6.2 Geometrie und Herstellung der Prüfkörper 164 6.2.1 Prüfkörper zum Bestimmen der Haftfestigkeit vor und nach künstlicher Alterung 164 6.2.2 Scherprüfkörper für Kriechversuche 165 6.2.3 Vorbereiten und Konditionieren der Proben 166 6.3 Verfahren zur mechanischen Prüfung und zur künstlichen Alterung 168 6.3.1 Zug- und Scherversuche 168 6.3.2 Lagerung unter UV-Bestrahlung 170 6.3.3 Lagerung in Reinigungsmittellösung 171 6.3.4 Holzfeuchtewechsel bei +20 °C 172 6.3.5 Lagerung in schwefeldioxidhaltiger Atmosphäre 173 6.3.6 Kriechversuche 174 6.4 Auswertung der Versuchsergebnisse 176 6.4.1 Anfangsfestigkeit im Scherversuch 176 6.4.2 Anfangsfestigkeit im Zugversuch 181 6.4.3 Sichtbare Veränderungen der Klebschicht 183 6.4.4 Restfestigkeit nach Alterung 185 6.4.5 Analyse der Versagensmuster 189 6.4.6 Kriechverhalten 192 6.4.7 Restfestigkeit nach Vorbelastung 198 7 Experimentelle Untersuchungen an bauteilähnlichen Prüfkörpern 201 7.1 Untersuchungsprogramm und Methodik 201 7.1.1 Ziel der Untersuchungen 201 7.1.2 Materialien 202 7.1.3 Großer Scherprüfkörper 203 7.1.4 Herstellung der Prüfkörper 205 7.1.5 Versuchsprogramm – Bauteilversuche 207 7.2 Entwicklung eines Kriechprüfstands 210 7.2.1 Prüfrahmen 210 7.2.2 Lasteinleitung 211 7.2.3 Belastungsvorgang 212 7.2.4 Messtechnik und Monitoring 213 7.2.5 Modifikation für Kurzzeitversuche 214 7.3 Große Scherversuche unter Kurz- und Langzeiteinwirkung 215 7.3.1 Tragfähigkeit bei kurzzeitiger Lasteinwirkung 215 7.3.2 Spannungsverteilung im Glas 219 7.3.3 Kriechversuche mit 1000 Stunden Laufzeit 221 7.3.4 Verlängerte Kriechversuche am Klebstoff mit mittlerer Steifigkeit 226 7.3.5 Tragfähigkeit nach Vorbelastung 230 8 Bewertung und Handlungsempfehlung 231 8.1 Alterungsverhalten 231 8.2 Korrelation der Ergebnisse aus Fügeteil- und 233 Bauteilversuchen 8.2.1 Versuche bei kurzzeitiger Lasteinwirkung 233 8.2.2 Versuche bei langandauernder Lasteinwirkung 235 8.3 Der Vorzugsklebstoff und seine Einsatzgrenzen 238 8.4 Konstruktion 241 9 Zusammenfassung und Ausblick 243 9.1 Zusammenfassung 243 9.2 Ausblick 249 10 Literatur 253 11 Abbildungsverzeichnis 263 12 Tabellenverzeichnis 267 13 Bezeichnungen 268 Anhang A Materialkennwerte zur Klebstoffauswahl 271 B Klebverbindungen im Labormaßstab 287 C Bauteilähnliche Prüfkörper 373