Tesis sobre el tema "Structural construction; Solid Timber"

Under de så kallade rekordåren mellan 1961-1975 byggdes det totalt 920,000 lägenheter i flerbostadshus i Sverige, och idag finns omkring 850,000 av dessa kvar. Den vanligaste byggnadstekniken under perioden var med byggande av förtillverkade våningshöga fasadelement tillsammans med en platsbyggd bokhyllestomme med tvärgående bärande innerväggar och gavlar. Syftet med arbetet är att kontrollera om en våningspåbyggnad på ett referenshus från miljonprogrammet med bokhyllestomme är möjlig för att skapa nya lägenheter som medför ökade hyresintäkter för fastighetsägaren, och kan medverka till ökad variation i området arkitektonisk och öka lägenhetsutbudet. Arbetet ger information om vad som behöver kontrolleras och utredas vid uppstarten av ett påbyggnadsprojekt. Arbetet jämför och beskriver tre olika stomförslag på en våningspåbyggnad. Alternativen som tas upp är massivträstomme med bärande flerskiktskiva, prefabricerad betong – och stålstomme bestående av HD/F-plattor och VKR-pelare, och ett alternativ bestående av volymelement. Inventering av konstruktionen och bärförmågan hos den befintliga stommen visar att det finns bärförmåga kvar att utnyttja. Utförda kontroller undersöker bl.a. bärförmågan hos väggar, grundsulor, samt det befintliga vindsbjälklaget. Kontroller utförs även med hänsyn till stabilitet då byggnaden betraktas som en stel enhet med en fiktiv påbyggnad. Slutsatsen av detta arbete är att en våningspåbyggnad är fullt möjlig på referenshuset. Alternativet med massivträ klarar en fiktiv påbyggnad om tre våningar som valts som exempel i arbetet. Alternativet med en prefabricerad betong och-stålstomme kan maximalt byggas på med två extra våningar, sedan blir grundtrycket dimensionerande och begränsar antalet våningar för påbyggnaden till två.
During the so called ‘record years’ between 1961-1975 a total of 920,000 apartments were built in apartment buildings in Sweden. Today about 850.000 of these are still in use. The most common method of building during this period was by using prefabricated one-storey high façade units together with load-bearing interior cross walls and gable walls which were built on site. The purpose of this degree project is to find out if a storey extension on a reference-building from the so called ‘Million Programme’ with load-bearing interior cross walls is possible in order to create new apartments. If this is possible it would give an increase of income of rents to the owner of the apartment building and it could also contribute to an increase of variation in the area as regards both architecture and supply of apartments. This degree project gives information about what has to be checked and investigated before a storey extension project begins. This degree project compares and describes three different suggestions of structural construction systems for storey extensions. The alternatives dealt with are solid timber structural construction consisting of cross-laminated boards, a prefabricated concrete – and steel structural construction consisting of HD/F-elements and tube steel framing, and finally an alternative consisting of prefabricated building modules. The study of the structural construction and the load-bearing capacity of the existing building show that there is enough load-bearing capacity left to make use of. Performed checks investigate for example the load-bearing capacity of load-bearing walls, strip foundations as well as the existing loft floor. Checks are also performed with regard to the stability as the building is considered a stiff unit with a fictitious storey extension. The conclusion from this degree project is that a storey extension is fully possible on the reference-building. The alternative with a solid timber structural construction allows a fictitious storey extension with three additional storeys, which has been chosen as an example in this degree project. The alternative with the prefabricated concrete – and steel structural construction allows a fictitious storey extension of maximum two additional storeys, and then the ground pressure was dimensioning and limited the amount of additional storeys for the storey extension.

An integrated programme of experimental and analytical work was carried out to evaluate the nonlinear semi-rigid characteristics of timber connections using fully overlapping nails subjected to short duration lateral loading and moment. The investigation is part of a continuing programme of research at Napier University into the behaviour of timberjoints using fully overlapping nails as the connecting Z -1 mechanism. The effects of the factors and material properties that influence the behaviour of nailed joints were addressed in a structured and controlled way allowing semi-empirical models to be developed for the lateral load behaviour of rnulti-nailed timber joints using steel and plywood gusset plates. A quality control procedure was established for the testing programme and consistent standards were applied to the preparation and testing work. The semi-empirical models that were developed included for the effect of timber density: crussept late material effect- nail strength; number of nails: nail diameter; row spacing and the effect of the moisture content in the timber. They covered joints assembled with and without a gap between the timber and the gusset plates and for joints assembled with steel gusset plates, the effect of the predrill size used in the gusset plate was also investigated. The model results compared very well with the results from tests, accurately predicting the non-linear behaviour of the joints up to failure. An extensive analytical and experimental study was carried out to investigate the moment-rotation behaviour of these types ofjoints. Two linear arýd four non-linear models were developed for each type of joint and the efficiencies of the models were compared to detennine the one that best simulated the joint behaviour. The linear models consistently underestimated the capacity of the joint, giving conservative results. The best solutions were obtained by applying the torsion formula used for steel connections and incorporating the nail behaviour models developed for the non-linear lateral load joints. Account was taken of the non-linear behaviour of the connection and alternative models using fixed and moveable centres of rotation were developed. Very good comparisons were achieved between these models and the test results. A detailed comparison was made between the behaviour of the joints using the lateral load displacement models and Eurocode 5 (EC5) and it was concluded that EC5 rules did not accurately simulate the behaviour of this type of joint. It was concluded that the nail spacing rules in the code did not apply to fully overlapping nails. A limit state design method based on the principles used in EC5 has been developed from the models for the design of joints using fully overlapping nails and subjected to lateral loading or moment. The semi-rigid behaviour of the joints was also investigated and it was concluded that to safely predict the response of structures assembled with fully, overlapping nails. the semi-rigid behaviour must be included for in the analysis procedure. Rigidity factors, end fixing moment reduction factors and the secant rotational stiffness coefficients for the joints were derived. It was also shown that where the analysis was limited to the serviceability limit state. a modified elastic method of analysis could be used and where it was beyond this state a non-linear method of analysis was required.

Topic of this Master's Thesis is a design and a statical evalution of a load bearing structure of an observation tower in Beskydy mountains. Ground plan of this structure is in a shape of a nonagon with a non-roofed interior space. Height of the observation tower is 38,5 m, the shape of a ground plan doesn't change with a radius of a circumscribed circle of 12 m. The structure is designed from glued laminated timber, solid wood and steel. Columns bear horizontal beams and their stiffness is ensured by horizontal and inclined reinforcing beams. Main load bearing columns, upper and lower beams are designed from glued laminated timber GL24h. Upper beams and beams of a gallery are designed from glued laminated timber GL36h. Horizontal stiffener is designed from solid wood C24. Central column, inclined beams, stairway, water slide cantilevers, rod and central rod are designed from steel of a strength class S235. Cantilever for gallery is designed from steel of a strength class S355. Connections are designed from steel elements. Statical evaluation, technical report and construction drawing are included

The topic of my diploma thesis is a design of a construction of a multipurpose building. The floor plan is of irregular shape with a maximal span of 35 metres. There are two buildings in shape of a hexagon, to which another building in shape of a half of a hexagon is connected. Part of the building is designed as a two-storey building and all parts are different in height. The hight of the designed building in its highest point is 13,5 metres. The load-bearing structure consists of glued laminated wood elements and raised wood with steel elements used as fasteners. The construction is designed alternatively from wood and steel. The static solution was made using the RFEM software.

Les projets de construction sont aujourd'hui confrontés à des défis importants pour réduire la grande quantité d'énergie employée quotidiennement pour les utilisations tels que le chauffage, l'électricité et l'eau chaude dans les bâtiments résidentiels et commerciaux, en particulier en Europe. De nombreux règlements de construction encouragent l'utilisation des matériaux biosourcés puisqu’ils semblent avoir des propriétés physiques supérieures en terme d'efficacité énergétique dans le secteur de la construction. L'utilisation de matériaux à faible teneur en carbone dans des structures telles que le béton de chanvre améliore le niveau d'isolation ainsi que l'absorption acoustique et diminue le poids de la structure du bâtiment, car ce matériau naturel fournit un agrégat à faible densité. Cette étude concerne le comportement mécanique de murs en bois, réalisés avec des planches croisées en bois CLT et des murs à panneaux d’OSB, sous l’effet de forces horizontales de cisaillement. Une approche théorique a été proposée pour prédire la performance latérale de la paroi CLT par rapport aux charges latérales ainsi qu’une comparaison entre les résultats théoriques et expérimentaux a été effectuée. Des essais expérimentaux ont été réalisés sur des murs de bois ayant deux formes différentes pour étudier et mettre en évidence les paramètres qui affectent significativement la résistance latérale du béton de chanvre en tant que matériau de remplissage. Des montants verticaux et des éléments de contreventement diagonaux de 2,5 mètres de hauteur et 1,25 mètres de largeur soumis à une compression ont été réalisés dans cette étude . Les résultats ont montré que le béton de chanvre apporte une légère contribution contre les charges latérales dans les murs verticaux de 1,25 mètres de largeur, ce qui signifie qu'une diminution de la largeur du mur de bois diminue significativement la contribution du béton de chanvre contre les charges latérales. Trois murs en bois de différentes longueurs (1,2 mètres, 1,6 mètres et 2,4 mètres) remplis de béton de chanvre ont été étudiés numériquement dans cette étude. D'après les résultats numériques, il était évident que la largeur du mur en bois joue un rôle principal dans la résistance latérale du béton de chanvre : lorsque la largeur du mur augmente, la résistance latérale du béton de chanvre s’accroît considérablement. De plus, le contact et la liaison entre le chanvre et les montants en bois affectent totalement la capacité de la résistance latérale du béton de chanvre en tant que matériau de remplissage dans les murs en bois
Construction projects nowadays face significant challenges to reduce the large amounts of daily energy usage for utilities such as heating, electricity and hot water in residential and commercial buildings – especially in Europe. Many building regulations encourage the use of bio-based materials with superior physical properties for energy efficiency in the construction sector. The use of low-carbon material in structures such as hemp concrete, improves the insulation level and sound absorption and simultaneously decreases the weight of the building structure, as this natural material provides low-density aggregate. This study aimed to investigate the mechanical behaviour of timber frame walls against lateral loads. Cross-laminated timber walls (CLT) and Oriented Strand Board (OSB) were used in this study in order to examine the global lateral strength of timber walls. A theoretical approach has been proposed to predict the lateral performance of CLT wall against lateral loads and a comparison between the theoretical and experimental results has been conducted. Experimental testing was undertaken on a full-size example of two different designs of timber walls to investigate and highlight the parameters that significantly affect the lateral resistance of hemp concrete as infill material. Vertical studs and diagonal bracing elements under compression were used in this study, with dimensions of 2.5m height and 1.25m length. The results showed that hemp concrete makes a slight contribution against lateral loads in vertical stud timber wall of length 1.25m, which means that decreasing the length of timber wall significantly decreased the hemp concrete contribution against lateral loads. Three timber walls with different lengths (1.2m, 1.6m and 2.4m) filled with hemp concrete have been examined numerically in this study. Based on the numerical results, it was obvious that the length of the timber wall plays a major role in the lateral strength of hemp concrete, as increasing the wall length significantly increased the lateral strength of hemp concrete. Also, the contact and bonding between hemp material and timber studs significantly affected the lateral load carrying capacity of hemp concrete as infill material in timber frame walls

A classificação estrutural de peças de madeira possibilita melhor utilização do material, separando as peças de acordo com a sua resistência estimada. Nesse processo é feita a classificação visual, de grande importância no caso de madeiras do gênero pinus, e a classificação mecânica por meio de testes não destrutivos com objetivo de estimar o módulo de elasticidade. Com esse objetivo, além de ensaios de flexão estática, podem ser aplicados métodos dinâmicos baseados em medições das frequências naturais e densidade do material para a determinação do módulo de elasticidade da madeira. Nesse sentido o objetivo deste trabalho foi avaliar a eficiência do aparelho portátil Brookhuis Micro Timber Grader (MTG) na estimativa do módulo de elasticidade por meio de ensaios não-destrutivos de vibração longitudinal. Para tanto, foi utilizado um lote de peças estruturais de madeira da espécie Pinus elliottii classificado visualmente. Os resultados obtidos por esse aparelho foram comparados com os resultados de módulo de elasticidade obtidos em ensaio de flexão estática. Tendo em vista a sua praticidade, é recomendável a utilização deste método para a classificação estrutural de peças serradas de madeira. A classificação visual agregada a classificação mecânica são essenciais para a utilização do Pinus em vigas laminadas coladas, construções industrializadas de madeira e do sistema construtivo em woodframe.
The structural grading of wood allows better use of the material, sorting the specimen according to their estimated strength. In this process the visual grading is a fundamental matter in use of the structural Pinus elliottii and also the mechanical grading obtained by non-destructive methods in order to estimate the modulus of elasticity. For this purpose, in addition to the static bending tests, dynamic methods based on measurement of the natural frequencies and density of the material to determining the modulus of elasticity (MOE) of timber can be applied. The objective of this study was to evaluate the efficiency of portable device Brookhuis Micro Timber Grader (MTG) in estimating the modulus of elasticity by non-destructive testing of longitudinal vibration. It was used structural pieces of wood species Pinus elliottii rated visually. The results obtained by this device was compared with the modulus of elasticity results obtained in static bending tests. Given its convenience and low cost, it is recommended to use this method for structural grading of timber sawn pieces. The visual and stress grading are essencial for the use of Pines in glued laminated timber, industrilization timber constructions and woodframe constructions.

La mixité bois-béton est une solution intéressante dans le domaine des ouvrages d'art pour la réalisation de ponts, et dans le domaine du bâtiment dans la confection de planchers mixtes bois-béton. Le laboratoire Navier travaille depuis plusieurs années au développement du procédé par collage appliqué aux structures mixtes bois-béton. En effet, cette technique d'assemblage permet d'assurer une connexion quasi-parfaite entre le bois et le béton, contrairement aux techniques d'assemblage usuelles (connecteurs métalliques). Des travaux antérieurs ont montré la bonne performance de structures mixtes collées bois-béton du point de vue de leur tenue mécanique en fatigue. Cependant la connexion par collage nécessite une étude complémentaire concernant la durabilité de l'assemblage collé bois-béton, en particulier lorsque la structure mixte est soumise à des conditions hygrométriques variables. Les travaux menés pendant la thèse ont pour objectifs de déterminer les facteurs qui influent sur la tenue de ces assemblages collés sous chargement hydrique ; ils se divisent en 3 parties :-Deux parties expérimentales :(1)Des tests de cisaillement « Push-Out », en collaboration avec le Laboratoire Départemental d'Autun, ont permis d'évaluer l'effet des propriétés élastiques de l'adhésif sur la tenue en cisaillement de l'assemblage. L'objet de cette étude expérimentale est de valider un choix de colle pour ce type d'assemblage, prenant en compte un vieillissement hydrique, en se basant sur la capacité maximale atteinte en cisaillement, et le mode de rupture de l'assemblage. (2)Parallèlement aux tests de cisaillement, l'effet de chargements hydriques sur la tenue d'assemblages collés bois-béton a été étudié. L'analyse du comportement hydrique de la structure a été réalisée par la technique de corrélation d'image (DIC) sur des assemblages bois-béton collé de petite taille. Ces mesures de déformations locales ont permis de localiser des zones d'endommagement liées notamment aux déformations hydriques du bois empêchées par l'interface collée. Les effets des propriétés élastiques de l'adhésif, de la géométrie du bois (notamment sa structure et le sens des cernes par rapport au plan de collage) ainsi que du comportement mécanique du matériau cimentaire ont été étudiés.- Une partie numérique :(3) Un modèle numérique par éléments finis a été validé en comparant les résultats numériques aux cartes de déformation obtenues expérimentalement. L'analyse numérique a permis de quantifier les contraintes induites au niveau de l'interface en relation avec les déformations hydriques empêchées par l'interface collée et de prévoir le comportement à l'échelle 1 de structures mixtes. Ces différentes investigations ont permis de proposer des solutions optimisant ce type de connexion et de définir des conditions de mise en œuvre et d'utilisation de ces assemblages
The wood-concrete composite is an interesting solution in the field of Civil Engineering to create high performance bending elements for bridge, as well as in the building construction for the design of wood-concrete floor systems. The Navier laboratory has been working for many years on the development of the bonding process as applied to wood-concrete composite structures. Contrary to conventional joining connectors (metal connectors), this assembling technique does ensure an almost perfect connection between wood and concrete. Previous work has already shown good performances of glued wood-concrete composite structures in terms of mechanical fatigue. However, the bonding connection requires additional research on the long-term behaviour of glued wood-concrete composites, especially when this structure is subjected to variable hygrometric conditions. The work undertaken during this thesis aims at determining the factors which induce damages on these glued wood-concrete assemblies under hygrometric loading; the research is divided into 3 parts:-Two experimental parts:(1)"Push-Out" shear tests conducted in collaboration with the Departmental Laboratory of Autun, were used to assess the effect of the elastic properties of the resin on the shear strength of the assembly. This experimental study aims at validating the adhesive of choice for this kind of connection, taking into account ageing under variable hygrometric conditions. Analysis is based on maximum shear capacity and on the failure mode of the assembly. (2)In addition to shear tests, the effect of hygrometric loading on the durability of glued wood concrete assemblies was examined. The analysis of the hydric behaviour of the structure was carried out by the digital image correlation (DIC) technique on small-sized glued wood-concrete assemblies. The measurements of the local deformations allowed us to locate areas of damage, particularly due to the hydric deformations of the wood prevented by the glued connection The effects of the elastic properties of the resin, the microstructure of the wood (including its structure and the direction of the annual rings) as well as the mechanical behaviour of the concrete material were examined.- A numerical part:(3) A numerical finite element model was validated by comparing the numerical results to the deformation maps experimentally obtained. Numerical analysis was used to quantify the stresses induced to the structure, in relation to hydric deformations prevented by glued connection. Moreover investigations at the full scale were conducted to evaluate the long-term behaviour under variable hygrometric conditions. These investigations were conducted in order to offer solutions aiming at optimizing this type of connection, and to define conditions for use of these glued assemblies

The thesis deals with the design and review of the supporting structure of the exhibition pavilion in the suburb of Brno. The design is shaped dome built over the octagonal floor plan with eight lateral niches. The pavilion is 30m wide and 8 meters tall.

The content of the master’s thesis is a design and evaluation of the timber construction of roofed footbridge for pedestrians and cyclists across the river Bělá in Jeseník in two different options of structure. The final version is solve in detail. It is a bridge with a span of 32 m and width of 4 m. The supporting structure is made of two two-hinged arch of glued laminated timber with lower deck and steel suspender. The bridge deck consists of two main girders, cross beams and stringers. Roof is from arches, roof beams, steel columns and cross beams. The stability of the whole construction is provided with horizontal longitudinal bracing in the plane of the deck and in the plane of the roof. The calculations are processed according to Czech technical norms ČSN EN.

Diploma thesis deals with creating the concept of container based modular building. The process of building is made by connecting module. Three block modules were designed. They could be created up to nine combinations (Up to nine combination might be created up by these). The modules are designed as a diffuse open wooden building with a warm flat roof. Family house is one of the possible combinations. Construction of building consists of two connected modules that are made like single-storey. Founded on earth screws. Under the construction is ventilated space. The building is situated on flat land (parcel) in Velké Němčice. The advantages of modular container buildings are good thermal properties, short time of construction and the possibility of connecting or disconnecting the modules.

The master's thesis deals with design and static assessment of loadbearing structure the timber viewtower on the hill Hostyn. The shape of the structure is very close oblate spheroid. Towers plan shape is a regular octagon whose outer diameter varies along the height. Tower in the footing and in the top measure 10,5 meters, at mid-height measure 6.5 meters. The height of the viewtower is 35 meters and view floor is located at a height of 30.5 meters. The main structure of tower consists outer towers curved wooden columns and interior steel column. Columns support the horizontal beams and bracing provide rigidity of the structure. The roof has a pyramid shape towers and tends to 17 °. Outer columns are designed from glued laminated wood GL24h, others carrying wooden beam are designed from solid timber C24 steel rods are designed from steel S235. Connections are solved using steel components. The work includes structural calculation, technical report and drawings.

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
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 content of this work was to carry out construction-technical survey of timber structures of the existing building in order to design an appropriate procedure for their reconstruction. The survey showed construction in an unsatisfactory to disrepair, so further work also includes the static calculation of new structures proposed instead of the current. Timber structure in the building has form of staircase, roof and ceiling construction. Newly designed the following types of stairs and roof trusses from which the lower belts are used as ceiling beams. The new proposal also includes possible roofing, roofing options, developed one of them. The work also includes drawings, bill of materials and cost estimate staircase structure and truss. Specialization in the field of civil engineering is represented by drawings of the new truss and passport (view of current state) whole object on parcel ST.74 / 1, land Tišnov (okr.Brno-venkov), the content of which was the basis for this work.

Tese no âmbito do Doutoramento em Engenharia Civil, apresentada à Faculdade de Ciências Tecnologia da Universidade de Coimbra
A madeira lamelada-cruzada (cross-laminated timber, CLT), tendência moderna em termos de construção em madeira, demonstra elevado potencial para sistemas maciços de construção de madeira. O conceito dos painéis CLT (camadas ortogonais) reduz significativamente a anisotropia dos painéis, garante maior estabilidade física e permite ligações mais fáceis e eficientes entre os elementos e destes com outros componentes da construção, tornando esses painéis uma solução versátil para suportar cargas fora/ e no plano dos mesmos. Este sistema possui vantagens significativas em relação à construção das tradicionais estruturas leves de madeira, abrindo um campo completamente novo para o uso da madeira na construção. Por outro lado, como se trata de um sistema maciço de madeira, é necessário um volume significativo de matéria-prima para produzir os painéis, aspeto que é apontado como uma das principais barreiras para a implementação do CLT de uma forma mais abrangente, porventura devido aos custos associados. Neste contexto, o objetivo da presente tese consistiu no desenvolvimento de uma solução de painel alternativa, ou pelo menos complementar, baseada em CLT, mas utilizando menos quantidade de madeira, combinando desempenho mecânico com melhor isolamento térmico e peso reduzido. A solução desenvolvida, denominada madeira isolada cruzada (cross-insulated timber, CIT), consiste em substituir a camada interna de um painel CLT de cinco camadas por uma à base de material de isolamento (espuma rígida de poliuretano), tendo, por isso, algumas semelhanças com o conceito de painel de madeira estrutural isolado (SIP). Os principais aspetos focados nesta tese, tendo em vista o desenvolvimento do painel incluem: (i) a definição da estrutura do painel e dos possíveis materiais para a sua constituição; (ii) a caracterização dos materiais selecionados para o desenvolvimento do painel, incluindo as camadas adesivas; (iii) a caracterização mecânica dos painéis; (iv) a otimização funcional e económica dos painéis; (v) a avaliação do impacte ambiental dos painéis; (vi) a caracterização acústica dos painéis; e (vii) o desenvolvimento de sistemas de conexão para os painéis. No primeiro aspeto, foi definida uma estrutura composta por um núcleo em espuma rígida de poliuretano entre dois pares de camadas cruzadas em madeira de Pinho bravo. Em alternativa, para as faces exteriores dos painéis, foi também considerada a Acácia Austrália. No segundo aspeto, os resultados de caracterização dos materiais permitiram verificar o comportamento complexo da espuma de poliuretano, tendo-se observado um comportamento não-linear e rotura dúctil em compressão e um comportamento linear e rotura frágil em tração. Da adesão entre materiais, concluiu-se que as adoção de pressões de aperto mais elevadas conduzem a uma melhor adesão dos mesmos e, dos ensaios de envelhecimento, concluiu-se que ao invés de uma redução da resistência, particularmente no poliuretano, houve um aumento da mesma devido à pós-reticulação do material. No terceiro aspeto, foi possível verificar que o modo de rotura dominante nos ensaios de flexão foi o corte do núcleo. Os modelos analíticos identificados na revisão do estado-da-arte descreveram bem o comportamento inicial observado (linear) e, para descrever a fase não-linear observada, os modelos numéricos desenvolvidos demonstraram um bom nível de precisão. No quarto aspeto, concluiu-se que a exigência de um desempenho térmico mínimo (envolvente exterior do edifício) torna a solução de painel desenvolvido na tese mais competitiva face aos painéis CLT. No quinto aspeto, através de uma análise de ciclo-de-vida, concluiu-se que a produção de poliuretano e a assemblagem do painel constituem os processos de produção com maior impacte ambiental; dos cenários de fim-de-vida considerados, a opção de incineração com recuperação de energia revelou ser a que implica menores impactes. Da comparação com sistemas de CLT, concluiu-se que o painel desenvolvido implica, de uma forma geral, maiores impactes. No sexto aspeto, verificou-se, o menor isolamento dos painéis de CIT face aos de CLT de igual espessura, devido à menor massa. Os modelos analíticos identificados no estado-da-arte para painéis sanduiche não se revelaram adequados para avaliação do isolamento a sons aéreos dos painéis, pelo que o modelo de Sharp para elementos isotrópicos e homogéneos com uma adaptação revelou uma melhor descrição dos mesmos; para descrição do isolamento a sons de percussão, a lei do invariante revelou-se eficaz. No sétimo aspeto foram desenvolvidas várias ligações, sendo que uma delas foi testada experimentalmente, e cuja resistência se enquadrou dentro do previsto pelos modelos analíticos identificados no estado-da-arte. Globalmente, o estudo realizado nesta tese mostrou que os painéis desenvolvidos têm potencial para complementar os atuais sistemas em CLT, nomeadamente no que diz respeito ao aos elementos da envolvente exterior.
Cross-Laminated Timber (CLT), a modern trend in timber construction, shows high potential for massive timber construction systems. Compared to traditional systems, the CLT panels’ layout (crosswise layers) significantly reduces the anisotropy of the panels, guarantees higher physical stability and allows for easier and more efficient connections between elements and other building components, making these panels a versatile solution to bear both out-of-plane and in-plane loads. This system has also significant advantages with respect to traditional wood light-frame construction, opening a completely new field for the use of timber in construction. On the other hand, as this is a massive wood system, a significant volume of wood raw material is required to produce the panels and this is pointed out as one of the main barriers for CLT implementation, perhaps due to the associated costs. In this context, the objective of the present thesis consisted of the development of an alternative, or at least complementary, CLT based panel solution but using less amount of wood, combining mechanical performance with improved thermal insulation and reduced weight. Such solution, named cross insulated timber (CIT), consists of replacing the inner layer of a five-layer CLT panel by an alternative one made of insulation material (polyurethane rigid foam), and thus having some similarities with the structural insulated timber panel (SIP) concept. The main aspects that are focused on this thesis for the panel development, include: (i) the definition of the panel layout and potential materials for its constitution; (ii) the characterization of the selected materials for the panel development, including the adhesive layers; (iii) the mechanical characterization of the panels; (iv) the functional and economic optimization of the panels; (v) the evaluation of the environmental impact of the panels; (vi) the acoustic characterization of the panels; (vii) the development of connection systems for the panels. In the first aspect, a structure consisting of a polyurethane core between two pairs of Maritime pine crossed layers was defined. As an alternative to this, for the exterior faces of the panels, Acacia Australia was considered. In the second aspect, the results of material characterization tests allowed to verify the complex behaviour of the polyurethane foam, which presents non-linear behaviour and ductile failure in compression, and linear behaviour and brittle failure in tension. From the adhesion between materials, it was concluded that the adoption of higher bonding pressures leads to better adhesion of the same ones and, from the ageing tests, it was concluded that instead of a reduction in strength, particularly in polyurethane, there was a strength increase due to additional cross-linking due to post-curing. In the third aspect, it was possible to verify that the dominant failure mode in the bending tests was core shearing. The analytical models identified in the state-of-the-art review described well the observed initial behaviour (linear) and, to describe the observed nonlinear phase, the numerical models developed demonstrated a good level of precision. In the fourth aspect, it was concluded that the requirement of a minimum thermal performance (in the case of the exterior envelope of the building) makes the panel solution more competitive against CLT panels. In the fifth aspect, through a life-cycle analysis, it was concluded that the production of polyurethane and the assembly of the panel constitute the production processes with the greatest environmental impact; among the considered end-of-life scenarios, the option of incineration with energy recovery proved to be the one with the least impacts. From the comparison with CLT systems, it was concluded that the developed panel presented, in general, greater impacts. In the sixth aspect, less insulation of the CIT panels compared to the CLT panels of equal thickness was registered, due to the lower mass. The analytical models identified in the state-of-the-art for sandwich panels did not prove to be suitable for assessing the airborne sound insulation of the panels, so the Sharp model for isotropic and homogeneous elements with an adaptation provided more accurate predictions; for describing the insulation to impact sounds, the invariant law proved to be effective. In the seventh aspect, several connections were developed, one of which was experimentally tested, and whose resistance fit within the predictions provided by the analytical models identified in the state-of-the-art. Overall, the study conducted in this thesis showed that the developed panels have the potential to complement the current CLT systems, namely concerning the elements of the external envelope.

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
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