Timber is becoming an increasingly popular construction material particularly due to its great environmental properties. Just alone around Linnaeus University in Växjö city, dozens of multistory buildings in timber have risen. As the demand for more timber construction is becoming popular, the understanding of timber design must evolve at the same pace. One of the most important parts of timber construction are the connections that hold everything together. One variable that is used to design connections is the embedment behavior. This thesis examined how the embedment behavior of a steel dowel in wood is influenced by moisture content, assembly history, and artificial cracks. In this case the assembly history refers to if the drilling and insertion of the steel dowel was done before or after drying or wetting the specimen. The idea behind the artificial crack was to achieve something similar to a real crack where the crack was created with a precision saw to separate the fibers parallel to the grain. The embedment behavior was studied by means of embedment strength, elastic- and plastic embedment stiffness. In total, 140 embedment experiments were conducted to study the embedment behavior of the dowel in wood. All embedment experiments were carried out parallel to the fiber direction using two species of wood, spruce and birch. Each experimental series had its own attributes to allow a comparison of how the embedment behavior is influenced by moisture content, assembly history, and artificial cracks. The data from the experiments was then used as input to create computer models where the beam on foundation modeling approach was used in conjunction with the finite element computer program Abaqus. A timber-steel-timber connection was modeled to study the influence of the side timber member thickness on the overall strength. The results of the experiments showed that the moisture content and the assembly history can potentially affect the embedment strength and the elastic, and the plastic embedment stiffness. The series that studied the influence of artificial cracks showed that mostly the embedment strength and elastic embedment stiffness are affected by artificial cracks. The numerical simulations indicated that the moisture profile from the experimental data had less influence on the strength for thicker timber side members than it did on thinner. In general, this thesis provides new insights and a better understanding of how the embedment behavior is influenced by moisture content, assembly history, and artificial cracks.

The research and application of Ultra-high Performance Concrete (UHPC) has been developed significantly within the last 1-2 decades. Due to the specific property of high strength capacity, it is potential to be used in bridge deck system without shear reinforcement so that it provides even lighter self-weight of the deck. However, one of the shear component, dowel action, has not been adequately investigated in the past. In this dissertation, a particular test was designed and carried out to fully investigate the dowel action response, especially its contribution to shear resistance. In addition, research on serviceability and fatigue behaviors were expanded as well to delete the concern on other factors that may influence the application to the deck system. Both experimental and analytical methods including finite element modeling, OpenSees modeling and other extension studies were presented throughout the entire dissertation where required.

Concrete pavements are a suitable alternative for high-traffic volume roads, concentrated loads and roads exposed to severe weather conditions. In Sweden, among other reasons, the scarcity of concrete pavements is attributed to the need for more national knowledge and expertise in the field. The most recent concrete pavement was constructed seventeen years ago in Uppsala. Concrete pavements are renowned for their longevity and durability. Jointed plain concrete pavements (JPCP) are the most frequent type of concrete pavements. However, it is important to note that the joints in concrete pavements are critical components that can lead to various distresses, necessitating rehabilitation. Rehabilitating concrete pavements is particularly challenging in areas with heavy traffic and requires substitute routes because of the imperative to maintain traffic flow during construction. Developing effective detours might involve significant alterations to the existing routes or building temporary roads, which entails substantial cost investment and time consumption. A literature review has been conducted to study the available methods that can be used to repair concrete pavements. The strategy for selecting a repair technique is based on rehabilitating the concrete pavement within a short work window, deterring traffic congestion and ensuring the long service life of the pavements. The study showed that the precast concrete technology based on the precast slab is a promising technology that effectively shortens the lane closure for repairing damaged pavements and produces durable pavements, thereby extending the service life of pavements. However, the construction or rehabilitation cost of concrete pavement using precast slabs is 1.6 to 4 times higher than that of conventional cast-in-place concrete. Therefore, rehabilitation using precast slabs is inappropriate for low-traffic roads and temporary routes. Joints are crucial for the rehabilitation of concrete pavements with precast slabs. The structural performance of concrete pavement is, however, greatly affected by the joints, as the presence of joints creates a discontinuity between adjacent slabs and thus diminishes the load transfer to the abutting slab. To maintain the structural integrity of the pavement system, dowel bars are used at the transverse joints. A numerical study has been conducted to evaluate the influence of various dowel-related parameters on the interaction between adjacent concrete slabs. The study revealed that the dowel bar’s position, mislocation and diameter had an obvious effect on joint efficiency, while the bond between the concrete slab and the dowel bar slightly affected the load transfer efficiency. It was also investigated that the dowel bar’s intended performance, i.e., load transfer efficiency, was reduced as the joint gap between adjacent slabs increased. / Betongbeläggningar är ett lämpligt alternativ för högtrafikerade vägar, koncentrerad belastning och vägar utsatta för svåra väderförhållanden. I Sverige är betongvägar sällsynta vilket bl.a. beror på brist på kunskap och kompetens. Den senaste betongvägen byggdes för sjutton år sedan i Uppsala.Betongbeläggningar är kända för sin långa livslängd och hållbarhet. Den vanligaste typen av betongvägar är fogade, oarmerade betongbeläggningar. Ändå är det viktigt att notera att fogarna i betongbeläggningar är kritiska komponenters om kan leda till olika olägenheter, vilket kräver rehabilitering. Att rehabilitera betongbeläggningar är särskilt utmanande i områden med intensiv trafik som kräver ersättningsvägar på grund av nödvändigheten att upprätthålla trafikflödet under reparationsarbetena. Att ta fram en effektiv omledning av trafiken kan innebära antingen väsentliga förändringar och förlängningar av befintliga rutter eller byggande av tillfälliga vägar, vilket medför betydande kostnadsinvesteringar och tidsåtgång. En litteraturöversikt har genomförts för att studera de tillgängliga metoderna som kan användas för att reparera betongbeläggningar. Strategin för valet av reparationsmetod bygger på att rehabilitera betongbeläggningen inom ett kort arbetsfönster, förhindra trafikstockningar och säkerställa lång livslängd för beläggningen. Studien visade att förtillverkade betongplattor är en lovande metod som effektivt förkortar avstängningen av körfält för att reparera skadad beläggning och producerar hållbara betongbeläggningar med lång livslängd. Rehabiliterings kostnaden för betongbeläggning med prefabricerade plattor är emellertid 1,6 till 4 gånger högre än den för konventionell platsgjuten betong. Därför är rehabilitering med förtillverkade betongplattor olämplig för vägar med låg trafik och temporära rutter. Fogar är vidare nödvändiga vid reparation med förtillverkade betongplattor.Betongbeläggningens strukturella prestanda påverkas dock kraftigt av fogar, eftersom förekomsten av fogar skapar en diskontinuitet mellan intilliggande plattor och därmed minskat lastöverföringen till den angränsande plattan. För att upprätthålla den strukturella integriteten hos beläggningssystemet används dymlingar i de tvärgående fogar. En numerisk studie har genomförts med olika parametrar för att utvärdera dymlingens inverkan på fogens effektivitet. Studien visade att dymlingens position, felplacering och diameter har en tydlig inverkan på fogens effektivitet, medan vidhäftningen mellan dymling och betongplatta enbart verkar ha en marginell inverkan på fogens effektivitet. Studien visade också att dymlingens prestanda, dvs. lastöverföringsförmågan, minskade då fogöppningen eller glappet mellan två närliggande plattor ökade. / <p>QC 240207</p>

No description available.

This study investigated the vibration serviceability of timber structures with dowel-type connections. It addressed the use of such connections in cutting-edge timber structures such as multi-storey buildings and long-span bridges, in which the light weight and flexibility of the structure make it possible that vibration induced by dynamic forces such as wind or footfall may cause discomfort to occupants or users of the structure, or otherwise impair its intended use. The nature of the oscillating force imposed on connections by this form of vibration was defined based on literature review and the use of established mathematical models. This allowed the appropriate cyclic load to be applied in experimental work on the most basic component of a dowel-type connection: a steel dowel embedding into a block of timber. A model for the stiffness of the timber in embedment under this cyclic load was developed based on an elastic stress function, which could then be used as the basis of a model for a complete connector. Nonlinear and time-dependent behaviour was also observed in embedment, and a simple rheological model incorporating elastic, viscoelastic and plastic elements was fitted to the measured response to cyclic load. Observations of the embedment response of the timber were then used to explain features of the behaviour of complete single- and multiple-dowel connections under cyclic load representative of in-service vibration. Complete portal frames and cantilever beams were tested under cyclic load, and a design method was derived for predicting the stiffness of such structures, using analytical equations based on the model for embedment behaviour. In each cyclic load test the energy dissipation in the specimen, which contributes to the damping in a complete structure, was measured. The analytical model was used to predict frictional energy dissipation in embedment, which was shown to make a significant contribution to damping in single-dowel connections. Based on the experimental results and analysis, several defining aspects of the dynamic response of the complete structures, such as a reduction of natural frequency with increased amplitude of applied load, were related to the observed and modelled embedment behaviour of the connections.

O trabalho tem por finalidade o estudo teórico e experimental de ligações em estruturas de madeira com cavilhas de madeira de seção cilíndrica impregnadas com resinas estirênicas. A impregnação da madeira tem como objetivos: diminuir o processo de degradação, retardação ao fogo, melhorar a estabilidade dimensional e aumentar as propriedades de resistência e elasticidade da madeira. Foram determinados experimentalmente as características de resistência e elasticidade do material e posteriormente realizados ensaios de ligações padronizados com solicitação paralela e normal às fibras. Os resultados dos ensaios mostram aumento na resistência de compressão normal até 292% e aumento de 80% no limite de proporcionalidade da ligação. A madeira utilizada para a impregnação foi o Pinus de reflorestamento. / The aim of this work is a theorytical and experimental studies of joints in timber structures with wooden dowels of circular cross section impregnated with styrenic resins. The objetives of wood impregnation are to decrease the deterioration process, to promote fire retardation, to improve dimensional stability and mainly increase the compression strength and stiffiness of wood. The strength and stiffness properties of the material are determined. Standard joints tests are carried out in compression both parallel and perpendicular to grains. The test results increases of compression perpendicular strength up to 292% and the up to 80% proportional limit joint. The wood used for impregnation was Pinus from reforestation sites.

A análise de painéis de concreto armado submetidos a corte puro é um tópico que tem recebido atenção de pesquisadores ao longo dos anos. Isto se deve, principalmente, à dificuldade encontrada na aplicação do carregamento e das condições de vinculação sobre a estrutura. Esta dificuldade é constatada tanto experimentalmente como na análise numérica. O objetivo deste trabalho é apresentar um modelo numérico para simular o comportamento de painéis de concreto simples e de concreto armado submetidos ao corte. Na análise computacional via Elementos Finitos, será utilizado um modelo de fissura incorporada que considera a contribuição da armadura no equilíbrio interno de forças do elemento. Estes modelos se baseiam no conceito de descontinuidades incorporadas dentro de elementos finitos padrão. O modelo incorporado implementado é uma continuação dos trabalhos desenvolvidos por d’Avila (2003) e Brisotto (2006), baseados no modelo de Dvorkin, Cuitiño e Gioia (1990). O modelo de transferência de tensão por aderência de Russo, Zingone e Romano (1990) foi usado por d’Avila para incluir a contribuição da armadura no equilíbrio interno de forças do elemento. Para representar as barras de aço da armadura, é utilizado o modelo incorporado desenvolvido por Elwi e Hrudey (1989) que permite a disposição arbitrária das barras no interior dos elementos de concreto. Os resultados dos ensaios numéricos de painéis de concreto armado submetidos ao corte puro com diferentes taxas de armadura são comparados com os resultados experimentais apresentados por Vecchio (1981). São incluídos dois diferentes modelos de efeito de pino (resistência ao corte das barras da armadura), analisando-se a influência dos mesmos no comportamento dos painéis ensaiados. O efeito do engrenamento dos agregados na fissura também foi estudado. Vários painéis com diferentes formas de ruptura experimental foram simulados, obtendo-se respostas muito boas para a maioria deles. Comparações da resposta tensão tangencial x distorção com e sem efeito de pino foram feitas, verificando-se a grande importância deste efeito na resposta global. / The analysis of reinforced concrete panels submitted to in-plane shear has received the attention of researchers along the years. It is mainly due to the difficulty to simulate the application of the external loads and the structural boundary conditions. The purpose of this work is to present a numerical model to represent reinforced concrete panels submitted to inplane shear. In the computational analysis via Finite Elements, an embedded crack model that considers the inclusion of the reinforcement contribution in the internal force equilibrium of the element is presented. This type of model is based in discontinuities embedded into standard finite elements. The implemented formulation uses the model presented by Dvorkin, Cuitiño and Gioia (1990), which does not have the reinforcement contribution in the element internal equilibrium. The adherence stress transfer model of Russo, Zingone and Romano (1990) is used to include this reinforcement contribution. An embedded model was employed to represent the reinforcement bars, allowing that they can be placed in an independent position and shape in the FEM elements. The numerical results are compared with Vecchio’s work. Also are included two different dowel action models (transversal shear resistance of the bars) and is studied their influence in the panels’ behavior. Panels with different experimental rupture modes were simulated with good responses in the most cases. Comparisons of shear stress x shear strain curve with and without dowel action are performed, showing the importance of this effect on the global response.

<p>Joints are critical parts of timber structures, transmitting static and dynamic forces between structural members. The ultimate behavior of a loaded building depends strongly on the structural configuration and the capacity of the joints. The collapse of a whole building or less extensive accidents that may occur is usually starting as a local failure inside or in the vicinity of a joint. Such serious failures have recently occurred in our Nordic countries. Especially the collapse of two large glued laminated timber structures clearly indicates the need of an improved joint design. The trend toward larger and more complex structures even further increases the importance of a safer design of the joints.</p><p>An aim of this partly experimental and partly numerically based thesis has been to investigate if steel-to-timber dowel joints are affected by moisture-induced stresses. The experimental results showed that the load-bearing capacity of the joints is reduced by such a moisture influence. Most of the decrease in load-bearing capacity observed was found in joints initially exposed to restrained shrinkage deformations caused by the presence of dowel fasteners in the joint area. The load-bearing capacity was, however, also found to decrease in joints exposed to an initial decrease in moisture without any fasteners present in the specimens during storage before loading. An explanation of this unexpected behavior is that moisture gradients cause tensile stresses. It is shown by numerical simulations that the moisture-induced stresses are so large that they may have a considerable influence on the joint behavior.</p><p>Use of contact-free measurement methods, used in some of the experimental tests, was in many ways found to be superior to traditional measurement techniques, but was also found to be a valuable complement to the numerical analysis performed. From numerical results obtained in combination with results from contact-free measurements several observations of considerable interest were made. For dowel-type joints loaded in tension parallel to the grain a strongly non-uniform strain distribution was found in the joint area. It was further observed that the shear and tensile strains were concentrated close to the fasteners in the joint area. These concentrations will influence the failure mode of the joint. A general observation was that the larger sized joints failed in a brittle manner.</p><p>Keywords: constraint stresses, contact-free measurement, dowel-type joints, humidity variations, moisture-induced deformations, timber structures</p>

Due to inadequate lateral stiffness, many reinforced concrete buildings are highly damaged or collapsed in Turkey after the major earthquake. To improve the behavior of such buildings and to prevent them from collapse, repair and/or strengthening of some reinforced concrete elements is required. One of the strengthening techniques is the use of CFRP sheets on the existing hollow brick masonry infill. While using the CFRP sheets their attachment to both structural and non-structural members are provided by CFRP anchor dowels. In this study, by means of the prepared test setup, the pull-out strength capacities of CFRP anchor dowels are measured. The effects of concrete compressive strength, anchorage depth, anchorage diameter, and number of fibers on the tensile strength capacity of CFRP anchor dowel are studied.

A análise de painéis de concreto armado submetidos a corte puro é um tópico que tem recebido atenção de pesquisadores ao longo dos anos. Isto se deve, principalmente, à dificuldade encontrada na aplicação do carregamento e das condições de vinculação sobre a estrutura. Esta dificuldade é constatada tanto experimentalmente como na análise numérica. O objetivo deste trabalho é apresentar um modelo numérico para simular o comportamento de painéis de concreto simples e de concreto armado submetidos ao corte. Na análise computacional via Elementos Finitos, será utilizado um modelo de fissura incorporada que considera a contribuição da armadura no equilíbrio interno de forças do elemento. Estes modelos se baseiam no conceito de descontinuidades incorporadas dentro de elementos finitos padrão. O modelo incorporado implementado é uma continuação dos trabalhos desenvolvidos por d’Avila (2003) e Brisotto (2006), baseados no modelo de Dvorkin, Cuitiño e Gioia (1990). O modelo de transferência de tensão por aderência de Russo, Zingone e Romano (1990) foi usado por d’Avila para incluir a contribuição da armadura no equilíbrio interno de forças do elemento. Para representar as barras de aço da armadura, é utilizado o modelo incorporado desenvolvido por Elwi e Hrudey (1989) que permite a disposição arbitrária das barras no interior dos elementos de concreto. Os resultados dos ensaios numéricos de painéis de concreto armado submetidos ao corte puro com diferentes taxas de armadura são comparados com os resultados experimentais apresentados por Vecchio (1981). São incluídos dois diferentes modelos de efeito de pino (resistência ao corte das barras da armadura), analisando-se a influência dos mesmos no comportamento dos painéis ensaiados. O efeito do engrenamento dos agregados na fissura também foi estudado. Vários painéis com diferentes formas de ruptura experimental foram simulados, obtendo-se respostas muito boas para a maioria deles. Comparações da resposta tensão tangencial x distorção com e sem efeito de pino foram feitas, verificando-se a grande importância deste efeito na resposta global. / The analysis of reinforced concrete panels submitted to in-plane shear has received the attention of researchers along the years. It is mainly due to the difficulty to simulate the application of the external loads and the structural boundary conditions. The purpose of this work is to present a numerical model to represent reinforced concrete panels submitted to inplane shear. In the computational analysis via Finite Elements, an embedded crack model that considers the inclusion of the reinforcement contribution in the internal force equilibrium of the element is presented. This type of model is based in discontinuities embedded into standard finite elements. The implemented formulation uses the model presented by Dvorkin, Cuitiño and Gioia (1990), which does not have the reinforcement contribution in the element internal equilibrium. The adherence stress transfer model of Russo, Zingone and Romano (1990) is used to include this reinforcement contribution. An embedded model was employed to represent the reinforcement bars, allowing that they can be placed in an independent position and shape in the FEM elements. The numerical results are compared with Vecchio’s work. Also are included two different dowel action models (transversal shear resistance of the bars) and is studied their influence in the panels’ behavior. Panels with different experimental rupture modes were simulated with good responses in the most cases. Comparisons of shear stress x shear strain curve with and without dowel action are performed, showing the importance of this effect on the global response.