Concrete deep beams with small shear span-to-depth (a/d) ratios are common elements in structures. However, there are few experimental results on the behaviour of FRP reinforced concrete deep beams and no specific modelling techniques exist in design codes for such members. The objectives of this study were to examine the shear behaviour of FRP reinforced concrete deep beams containing no web reinforcement and to develop a modelling technique. Test results of 12 large-scale specimens are reported where the primary variables included the a/d ratio, reinforcement ratio, member height, and concrete strength. The results showed that an arch mechanism was able to form in FRP reinforced concrete beams having a/d 2.1. A strut and tie modelling procedure adapted from CSA A23.3-04 was capable of accurately predicting the capacity of FRP reinforced concrete deep beams containing no web reinforcement while sectional shear models gave poor, but conservative, predictions. / Structural Engineering

Concrete bridges in Texas have developed large cracks in bent caps and pretensioned trapezoidal bridge girders. The bridges show premature concrete deterioration due to alkali-silica reaction (ASR) and delayed ettringite formation (DEF). There is concern that deterioration due to ASR/DEF may lead to a loss of structural capacity. However, there are no quantitative guidelines to relate the level of concrete deterioration due to ASR/DEF to structural performance. Using such guidelines, the need for rehabilitation of beams with ASR/DEF cracking can be assessed. The goal of this research was to determine the shear capacity of pretensioned trapezoidal box girder specimens exhibiting varying degrees of ASR and/or DEF cracking and to use the shear testing results to evaluate the severity of the problem that may exist in Texas bridge structures. To achieve this goal, beams that were severely deteriorated due to ASR/DEF over a period of more than ten years were transported to the University of Texas for testing to failure. Both severely deteriorated and uncracked beams were tested in shear. The test results were used to evaluate the shear performance of trapezoidal box beams affected by ASR/DEF. In addition, three different types of forensic analyses were conducted on the beams to understand the nature of the ASR/DEF cracks and severity of the deterioration. After testing, it is found that the shear capacity of the test specimens was not significantly reduced even with heavy ASR/DEF cracking. Assessment using current US design provisions for bridges or buildings (ACI 318-08 and AASHTO LRFD 2008) and the proposed provision from an earlier project (TxDOT Project 5253) yielded conservative estimates of strength. Results from forensic analyses provided a qualitative indication of ASR/DEF damage but did not correlate with the observed levels of ASR/DEF deterioration. / text

Across the State of Texas and many other areas of the world, relatively young concrete structures have developed signs of premature concrete deterioration. Large cracks form on the surface of the concrete due to expansive forces from alkali-silica reaction (ASR) and delayed-ettringite formation (DEF). The goal of this project is to assess the effect of ASR/DEF on the trapezoidal box beam bridges in the US 59 corridor and Katy Central Business District (CBD) HOV lanes in Houston, TX. Five dapped-end beams were rejected during the casting process and have been in storage at a local precast yard for nearly fifteen years. These beams have been subject to accelerated deterioration and represent the potential severity of the ongoing ASR/DEF distress within the dapped end regions of the in-service trapezoidal box beams. The results from five load tests, corresponding strut-and-tie models, and forensic investigation are used to provide insights into the relationship between the severity of the deterioration and the capacity margin. / text

No description available.

Experiments were conducted to investigate the shear behaviour of large deep beams subjected to uniform load. Six tests were performed on specimens with identical cross sections and reinforcing, but under different loading configurations. Variables included: span, degree of cracking prior to loading, proximity to a disturbed region near a reaction, and type of flexural stress on the loaded face. The findings indicate a specific set of variables resulting in unconservative predictions made using a strut-and-tie model for simply-supported beams subjected to uniform load, confirming and validating recent results by other researchers. A fanning strut model is proposed and is shown to provide more conservative results. The emerging trend of high capacity in continuous uniformly-loaded specimens is supported by the experimental results, as is the high capacity of specimens uniformly-loaded on their flexural tension face. Further, the high strength of specimens with suboptimal crack orientations supports recent experimental work.

Experiments were conducted to investigate the punching shear behaviour of thick slabs with identical spans and depths, subjected to monotonic point load conditions. Variables included: reinforcement ratio, column size, and reinforcement size. Analytical studies conducted as part of this thesis indicate that the current CSA A23.3 and the ACI 318 can be unconservative for thick slabs with low reinforcement ratios. The new fib Model Code provisions for punching offer an effective method for determining the full load-rotation behaviour of a slab up to failure, including accurate failure predictions. A summary of the background of current design procedures and standards will be presented, and a comparison between the different design equations and theories will be given. Based on the findings of this project, it is proposed that the provisions accepted by the fib Model Code should be considered for implementation in the CSA and ACI standards.

Experiments were conducted to investigate the shear behaviour of large deep beams subjected to uniform load. Six tests were performed on specimens with identical cross sections and reinforcing, but under different loading configurations. Variables included: span, degree of cracking prior to loading, proximity to a disturbed region near a reaction, and type of flexural stress on the loaded face. The findings indicate a specific set of variables resulting in unconservative predictions made using a strut-and-tie model for simply-supported beams subjected to uniform load, confirming and validating recent results by other researchers. A fanning strut model is proposed and is shown to provide more conservative results. The emerging trend of high capacity in continuous uniformly-loaded specimens is supported by the experimental results, as is the high capacity of specimens uniformly-loaded on their flexural tension face. Further, the high strength of specimens with suboptimal crack orientations supports recent experimental work.

Experiments were conducted to investigate the punching shear behaviour of thick slabs with identical spans and depths, subjected to monotonic point load conditions. Variables included: reinforcement ratio, column size, and reinforcement size. Analytical studies conducted as part of this thesis indicate that the current CSA A23.3 and the ACI 318 can be unconservative for thick slabs with low reinforcement ratios. The new fib Model Code provisions for punching offer an effective method for determining the full load-rotation behaviour of a slab up to failure, including accurate failure predictions. A summary of the background of current design procedures and standards will be presented, and a comparison between the different design equations and theories will be given. Based on the findings of this project, it is proposed that the provisions accepted by the fib Model Code should be considered for implementation in the CSA and ACI standards.

For architectural reasons, in some structural building systems, the need to change the direction of columns from one floor to another arises. One of the adopted solutions in the transition zone is to use a block of reinforced concrete to assist the transfer of loads between the columns. This solution is proposed by analogy to the blocks used in the transition from the superstructure to the infrastructure of a building, commonly called the pile caps. In this context, this work aims to study a three-dimensional strut-and-tie model applied to the design of reinforced concrete blocks used in the transition between rotated columns, from the results of elastic analysis of stresses and numerically evaluate the failure modes, last resistance and service conditions of the designed block, considering the physical non-linearity of the materials with a model of plasticity. The three-dimensional model was proposed linking plane models defined previously in studies of the author. It was found that the difference of the stresses between the proposed model and the plane model are not significant, confirming thereby the use of the plane model. From the nonlinear analysis, it was found that the load capacity of the investigated element is significantly greater than the applied load, by influence of the tensile strength of the concrete. This means that as the tensile strength of the concrete in the strut and tie model is not considered, is neglected much of the load capacity of the element. Furthermore, it was observed that the configuration of ruin occurred by yielding of steel in the armor called "main". With the results of the study, it was sought to contribute to propose a better solution for the transition region between rotated columns. / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Por motivos arquitetônicos, em alguns dos sistemas estruturais de edifícios surge a necessidade de modificar a direção de pilares de um pavimento para o outro. Uma das soluções adotadas na zona de transição de direção é a utilização de um bloco de concreto armado para auxiliar a transferência das cargas entre os pilares. Esta solução é proposta por analogia aos blocos utilizados na transição da superestrutura à infraestrutura de uma edificação, comumente chamado de blocos de fundação. Nesse contexto, o presente trabalho tem como objetivo estudar um modelo de bielas e tirantes tridimensional para o dimensionamento de blocos de concreto armado para transição entre pilares rotacionados, a partir dos resultados de análises elásticas de tensões, e avaliar numericamente os modos de falha, resistências últimas e condições de serviços do bloco dimensionado, considerando a não linearidade física dos materiais com um modelo de plasticidade. O modelo tridimensional proposto interliga modelos planos anteriormente definidos em estudos do autor. Verifica-se que a diferença entre os esforços do modelo proposto e o do modelo plano não são significativas, ratificando, com isso, a utilização do modelo plano. A partir das análises não lineares, verifica-se que a capacidade resistente do elemento estudado é significativamente maior que a solicitação aplicada, por influência da resistência à tração do concreto, ou seja, a não consideração da resistência à tração do concreto no modelo de bielas e tirantes despreza grande parte da capacidade resistente do elemento. Além disso, observa-se que a configuração de ruína ocorre pelo escoamento do aço na armadura chamada de "principal". Com os resultados do trabalho, busca-se contribuir com a proposição de uma solução mais adequada para a região de transição entre pilares rotacionados.

Made available in DSpace on 2015-03-26T13:28:03Z (GMT). No. of bitstreams: 1 texto completo.pdf: 2387307 bytes, checksum: f11d179178c73973dbcc9eaba047425e (MD5) Previous issue date: 2011-07-04 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This work presents an evaluation of the structural behavior of steel plane frames infilled with structural masonry of blocks of autoclaved aerated concrete, regarding the contribution of the masonry to the structure global stiffening, through the strut-and-tie model. Case studies were evaluated taking into account three steel plane frames and, subsequently, the model was applied to the project of steel buildings with four, six, and eight stories. First and second-order numerical analyses (nonlinear geometrical analysis) were performed to braced steel frames with bracing elements formed for bars of steel and masonry panels. The masonry panels were considered across strut-and-tie model. It is presented comparisons of the lateral displacements and the solicitant forces in the bars of strut-and-tie model to first and second-order analyses. The solicitant forces on the strut and tie were also compared to the structural resistance on these bars aiming to achieve the structural dimension of the masonry panel. Through the results obtained it is concluded that it is possible to substitute the bracing metal bars for the masonry panels until determined numbers of stories. This numbers depends on factors such as the stiffness of the frame and masonry panels, and the intensity applied. / Neste trabalho apresenta-se uma avaliação do comportamento estrutural de pórticos planos de aço preenchidos com alvenaria estrutural de blocos de concreto celular autoclavado, considerando a contribuição da alvenaria na rigidez global da estrutura, por meio de um modelo de bielas e tirantes. Para realização dos estudos de caso, foram avaliados três pórticos planos de aço e, posteriormente, o modelo foi aplicado ao projeto de edifícios de aço com quatro, seis e oito pavimentos. Foram realizadas análises numéricas de primeira e segunda ordem (análise não-linear geométrica) de pórticos de aço contraventados com elementos de contraventamentos formados por barras de aço e por painéis de alvenaria. Os painéis de alvenaria foram considerados por meio do modelo de bielas e tirantes. São apresentadas comparações dos deslocamentos laterais e dos esforços solicitantes nas barras do modelo de bielas e tirantes para as análises de primeira e de segunda ordem. Os esforços solicitantes nas bielas e nos tirantes também foram comparados com os esforços resistentes nessas barras, com vistas a efetuar o dimensionamento estrutural do painel de alvenaria. Os resultados obtidos permitem concluir que é possível substituir as barras de contraventamento metálico por painéis de alvenaria até um determinado número de pavimentos. Este número depende de fatores como a rigidez dos pórticos e dos painéis de alvenaria e a intensidade das ações aplicadas.