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yes / Test results of 24 reinforced concrete continuous deep beams are reported. The main variables studied were concrete strength, shear span-to-overall depth ratio (a/h) and the amount and configuration of shear reinforcement. The results of this study show that the load transfer capacity of shear reinforcement was much more prominent in continuous deep beams than in simply supported deep beams. For beams having an a/ h of 0.5, horizontal shear reinforcement was always more effective than vertical shear reinforcement. The ratio of the load capacity measured and that predicted by the strutand-tie model recommended by ACI 318-05 dropped against the increase of a/h. This decrease rate was more remarkable in continuous deep beams than that in simple deep beams. The strut-and-tie model recommended by ACI 318-05 overestimated the strength of continuous deep beams having a/ h more than 1.0.

The research conducted was sponsored by JVI of Pittsfield, Massachusetts. JVI has developed a steel embedded connection, referred to as a shooter. The shooter is provided in capacities, a 40 kip capacity shooter and a 50 kip capacity shooter. This steel connection is embedded near the end of a double-tee prestressed girder. Double-tee prestressed girders are a primary component used in the construction of parking garages. Typical double-tee lengths are 60 to 75 feet; however, for this research 20 ft long segments were cast and tested with the shooter installed. This project had three main goals. The first goal was to develop a preliminary design for the reinforcement around the shooter and test the shooters' capacity in the laboratory to determine if the stated capacity was correct. Four different designs were created, two designs for the 40 kip capacity shooter and 2 designs for the 50 kip capacity shooter. Each design was placed in one stem of the double-tee and tested at the laboratory. Results from these tests indicate that that each specimen achieved the stated capacity. However, failure was not a connection failure but a shear bond failure. The second goal was to take the information gathered from testing and develop a design model that could be used for other situations for this type of connection. The design model was created according to the guidelines in the ACI 318-08 code. Two different methods were used, a strut-and-tie model and a modified ACI code approach. From these designs it was determined that the strut-and-tie model should be used for the design of these connections; however, more research needs to be done before using the modified ACI code approach. The final goal was to determine if finite element analysis could be used to determine if the load at which large cracks that immediately proceed failure occur could be predicted. From this analysis it was determined that a load range could be predicted in which a crack could form as well as a range of what the transfer length of the strands could be. / Master of Science

Precast/Prestressed concrete girders are commonly used in bridge construction in the United States. The application and diffusion of the prestress force in a pretensioned girder causes a vertical tension force to develop near the end of the beam. Field surveys of the beam ends of pretensioned bridge girders indicate that many of the PCBT beams used in the Commonwealth of Virginia develop cracks within the anchorage zone region. The lengths and widths of these cracks range from acceptable to poor and in need of repair. Field observations also indicate deeper cross sections, very heavily prestressed sections, and girders with lightweight concrete tend to be most susceptible to crack formation. This research examined a new strut-and-tie based design approach to the anchorage zone design of the PCBT bridge girders used in Virginia. Case study girders surveyed during site visits are discussed and used to illustrate the nature of the problem and support the calibration of the strut-and-tie based model. A parametric study was conducted using this proposed design model and the results of this study were consolidated into anchorage zone design tables. The results of the parametric study were compared to the results obtained using existing anchorage zone design models, international bridge codes, and standard anchorage zone details used by other states. A set of new standard details was developed for the PCBT girders which incorporates elements of the new design approach and is compatible with the anchorage zone design aids. A 65 ft PCBT-53 girder was fabricated to verify the new strut-and-tie based design model. This girder contained anchorage zone details designed with the new model. The new anchorage zone details were successful at controlling the development of anchorage zone cracks. The new design approach is recommended for implementation by the Virginia Department of Transportation. / Master of Science

O modelo de bielas e tirantes apresenta como uma de suas vantagens a generalidade, ou seja, é capaz de representar, de modo aproximado, porém realista e sistemático, grande parte dos elementos de concreto estrutural da atualidade. Além disso, permite ao engenheiro fácil visualização físico-intuitiva do comportamento do concreto estrutural. Por outro lado, o modelo ainda tem um enorme potencial não aproveitado. Ainda não se tem um critério exato para determinação dos nós e das seções transversais das bielas de alguns elementos. Apesar de haver certas incertezas no caso de vigas-parede e principalmente de blocos de fundação, nas vigas esses elementos do modelo podem ser determinados sem grandes dificuldades. Possivelmente, a solução seria variar as dimensões das bielas e as posições dos nós, ambas hipotéticas, a fim de confrontar várias situações com resultados experimentais. Daí a grande importância da difusão do modelo de bielas e tirantes: um maior número de análises de modelagens e de resultados de ensaios levará a um maior domínio sobre o modelo. Este trabalho consiste na análise de vigas de concreto armado utilizando modelos de bielas e tirantes. São apresentados os conceitos que levaram à concepção do modelo, desde a Analogia Clássica da Treliça, chegando aos critérios para verificação dos elementos da treliça e às recomendações atuais de normas e pesquisadores. Com o auxílio do programa computacional CAST (2000), foram modeladas quatro vigas, sendo as três primeiras biapoiadas sem descontinuidades e a quarta com balanço e descontinuidade geométrica (abertura na alma). A primeira viga biapoiada teve algumas de suas características iniciais alteradas a fim de gerar o segundo e o terceiro modelos, procurando-se estabelecer limites de carregamentos e análises comparativas. Os resultados das modelagens permitiram comparações com os resultados das verificações realizadas segundo os critérios da NBR 6118:2003 e do MC CEB-FIP (1990) e, permitiram também, identificar os aspectos de maior dificuldade na concepção de um modelo de bielas e tirantes e os pontos críticos dos mesmos, nos quais há maior possibilidade de falha nas verificações / One of the main advantages presented by the strut-and-tie model is generality. This model is able to approximately represent, in a realistic and systematic way, the majority of today’s reinforced concrete elements. Furthermore, it allows the physics-intuitive visualization of the behavior presented by structural concrete. On the other hand, its potentials are not fully explored yet. Up to date, there is no accurate criterion for the determination of nodes and transverse sections of some strut elements. Despite presenting some uncertainties related to the determination of wall-beams (and mainly of foundation blocks), the model can determine beams without major difficulties. Probably, the key is to vary the dimensions of the struts and the positions of the nodes, both hypothetical, in order to confront various situations with experimental data. Hence, it is very important to diffuse the strut-and-tie model: the bigger the number of modeling analysis and experimental data, the better the comprehension of the model. This work aims to analyze reinforced concrete beams employing the strut-and-tie model. Here are presented the concepts that led to the development of the model, ranging from the Truss Classic Analogy to the criteria employed to verify truss elements and the recommendations from researchers and established standards (rules or norms). Four examples of beams were modeled. Three of them were double-based and the fourth presented balance and no geometric discontinuity (with an opening). Some of the characteristics of the first double-based beam were altered in order to generate the second and the third model, thus establishing loading limits and comparative analysis. The modeling allowed comparisons between the verifications performed in accordance with the NBR 6118:2003 and MC CEB-FIP criteria. It also allowed the identification of major difficulties and critical aspects related to the development of struts and ties, the ones that are most prone to failure in the verification process

Este trabalho estuda o comportamento estrutural de blocos sobre estacas em concreto armado situados em divisas de terrenos. Foi feita revisão bibliográfica abordando os assuntos de blocos de coroamento, vigas de equilíbrio, modelo de bielas e tirantes e um breve comentário sobre o programa computacional Diana (2010). O trabalho apresenta um roteiro para análise estrutural e dimensionamento de vigas de equilíbrio sobre estacas com pilar excêntrico ao apoio. É apresentado um exemplo feito por Andrade (1989), comparado com o método proposto por Burke (1979) e com análise numérica. Além deste, foram analisados casos de projetos reais utilizando o método Burke (1979) adaptado neste trabalho. Alguns desses exemplos foram modelados em regime elástico e linear no programa computacional Diana (2010). São apresentadas comparações de resultados obtidos com o método Burke (1979) e análise numérica, comprovando a eficácia desse método. Em todos os exemplos estudados o método proposto por Burke (1979) indicou bons resultados quando comparados com os encontrados em análise computacional. A dissertação apresenta soluções para projetos de bloco sobre estacas, situados em divisas de terrenos e associados a vigas de equilíbrio. / This research investigates the structural behavior of reinforced concrete blocks piles located on the limit of land. Literature review was done about blocks piles, balance beams, strut and tie model and a short comment about the Diana computer program (2010). The dissertation presents a roadmap for structural analysis and sizing of balance beams on stakes with eccentric support pillar. An example, which was studied by Andrade (1989), is compared with the same example done using the method proposed by Burke (1979) and with numerical analysis. In addition to this, are analyzed real cases of projects using the method of Burke (1979). Some of these examples were modeled in linear and elastic characteristics using Diana program computer (2010). Here, it is presented comparisons between the method proposed by Burke (1979) and numerical analysis. It is presented comparisons between the method Burke (1979) and numerical analysis, proving the effectiveness of this method. In all examples studied the method proposed by Burke (1979) provided with good accuracy the results for computer analysis. The conclusion presents suggestions for projects of block piles located in limit of land associated with balance beams.

Significant diagonal cracking in reinforced concrete inverted-T (IT) straddle bent caps has been reported throughout the State of Texas. Many of the distressed structures were recently constructed and have generally been in service for less than two decades. The unique nature of the problem prompted a closer look into the design and behavior of such structural components. A preliminary investigation highlighted outdated design requirements and a scarcity of experimental investigations pertaining to inverted-T bent caps. This research project (TxDOT Project 0-6416, Shear Cracking in Inverted-T Straddle Bents) aims to improve current understanding of the behavior of inverted-T caps, while providing updated design provisions. In order to develop strength and serviceability guidelines for inverted-T beams, an extensive experimental program was developed. This series of large scale tests was used to evaluate the strength and serviceability of IT deep beams in relation to the following parameters – shear span-to-depth (a/d) ratio, web reinforcement ratio, ledge height, ledge length, number of point loads, and member depth. This report focuses mainly on results from a first series of tests conducted within this experimental program. / text

Este trabalho estuda o comportamento estrutural de blocos sobre estacas em concreto armado situados em divisas de terrenos. Foi feita revisão bibliográfica abordando os assuntos de blocos de coroamento, vigas de equilíbrio, modelo de bielas e tirantes e um breve comentário sobre o programa computacional Diana (2010). O trabalho apresenta um roteiro para análise estrutural e dimensionamento de vigas de equilíbrio sobre estacas com pilar excêntrico ao apoio. É apresentado um exemplo feito por Andrade (1989), comparado com o método proposto por Burke (1979) e com análise numérica. Além deste, foram analisados casos de projetos reais utilizando o método Burke (1979) adaptado neste trabalho. Alguns desses exemplos foram modelados em regime elástico e linear no programa computacional Diana (2010). São apresentadas comparações de resultados obtidos com o método Burke (1979) e análise numérica, comprovando a eficácia desse método. Em todos os exemplos estudados o método proposto por Burke (1979) indicou bons resultados quando comparados com os encontrados em análise computacional. A dissertação apresenta soluções para projetos de bloco sobre estacas, situados em divisas de terrenos e associados a vigas de equilíbrio. / This research investigates the structural behavior of reinforced concrete blocks piles located on the limit of land. Literature review was done about blocks piles, balance beams, strut and tie model and a short comment about the Diana computer program (2010). The dissertation presents a roadmap for structural analysis and sizing of balance beams on stakes with eccentric support pillar. An example, which was studied by Andrade (1989), is compared with the same example done using the method proposed by Burke (1979) and with numerical analysis. In addition to this, are analyzed real cases of projects using the method of Burke (1979). Some of these examples were modeled in linear and elastic characteristics using Diana program computer (2010). Here, it is presented comparisons between the method proposed by Burke (1979) and numerical analysis. It is presented comparisons between the method Burke (1979) and numerical analysis, proving the effectiveness of this method. In all examples studied the method proposed by Burke (1979) provided with good accuracy the results for computer analysis. The conclusion presents suggestions for projects of block piles located in limit of land associated with balance beams.

O modelo de bielas e tirantes apresenta como uma de suas vantagens a generalidade, ou seja, é capaz de representar, de modo aproximado, porém realista e sistemático, grande parte dos elementos de concreto estrutural da atualidade. Além disso, permite ao engenheiro fácil visualização físico-intuitiva do comportamento do concreto estrutural. Por outro lado, o modelo ainda tem um enorme potencial não aproveitado. Ainda não se tem um critério exato para determinação dos nós e das seções transversais das bielas de alguns elementos. Apesar de haver certas incertezas no caso de vigas-parede e principalmente de blocos de fundação, nas vigas esses elementos do modelo podem ser determinados sem grandes dificuldades. Possivelmente, a solução seria variar as dimensões das bielas e as posições dos nós, ambas hipotéticas, a fim de confrontar várias situações com resultados experimentais. Daí a grande importância da difusão do modelo de bielas e tirantes: um maior número de análises de modelagens e de resultados de ensaios levará a um maior domínio sobre o modelo. Este trabalho consiste na análise de vigas de concreto armado utilizando modelos de bielas e tirantes. São apresentados os conceitos que levaram à concepção do modelo, desde a Analogia Clássica da Treliça, chegando aos critérios para verificação dos elementos da treliça e às recomendações atuais de normas e pesquisadores. Com o auxílio do programa computacional CAST (2000), foram modeladas quatro vigas, sendo as três primeiras biapoiadas sem descontinuidades e a quarta com balanço e descontinuidade geométrica (abertura na alma). A primeira viga biapoiada teve algumas de suas características iniciais alteradas a fim de gerar o segundo e o terceiro modelos, procurando-se estabelecer limites de carregamentos e análises comparativas. Os resultados das modelagens permitiram comparações com os resultados das verificações realizadas segundo os critérios da NBR 6118:2003 e do MC CEB-FIP (1990) e, permitiram também, identificar os aspectos de maior dificuldade na concepção de um modelo de bielas e tirantes e os pontos críticos dos mesmos, nos quais há maior possibilidade de falha nas verificações / One of the main advantages presented by the strut-and-tie model is generality. This model is able to approximately represent, in a realistic and systematic way, the majority of today’s reinforced concrete elements. Furthermore, it allows the physics-intuitive visualization of the behavior presented by structural concrete. On the other hand, its potentials are not fully explored yet. Up to date, there is no accurate criterion for the determination of nodes and transverse sections of some strut elements. Despite presenting some uncertainties related to the determination of wall-beams (and mainly of foundation blocks), the model can determine beams without major difficulties. Probably, the key is to vary the dimensions of the struts and the positions of the nodes, both hypothetical, in order to confront various situations with experimental data. Hence, it is very important to diffuse the strut-and-tie model: the bigger the number of modeling analysis and experimental data, the better the comprehension of the model. This work aims to analyze reinforced concrete beams employing the strut-and-tie model. Here are presented the concepts that led to the development of the model, ranging from the Truss Classic Analogy to the criteria employed to verify truss elements and the recommendations from researchers and established standards (rules or norms). Four examples of beams were modeled. Three of them were double-based and the fourth presented balance and no geometric discontinuity (with an opening). Some of the characteristics of the first double-based beam were altered in order to generate the second and the third model, thus establishing loading limits and comparative analysis. The modeling allowed comparisons between the verifications performed in accordance with the NBR 6118:2003 and MC CEB-FIP criteria. It also allowed the identification of major difficulties and critical aspects related to the development of struts and ties, the ones that are most prone to failure in the verification process

Yes / The test results on eight two-span deep beams made of self-compacting concrete (SCC) are presented and discussed in this paper. The main parameters investigated were the shear span-to-depth ratio, and the amount and configuration of steel reinforcement. All beams failed due to a major diagonal crack formed between the applied mid-span load and the intermediate support separating the beam into two blocks: the first one rotated around the end support leaving the other block resting on the other two supports. Both concrete compressive strength and web reinforcement had a major effect in controlling the shear capacity of the beams tested. For the shear span-to-depth ratio considered, the vertical web reinforcement had more influence on the shear capacity of the specimens than the horizontal web reinforcement. The shear provisions of the ACI 318M-11 are unconservative for most of the beams tested. Comparisons of test results with the strut-and-tie model (STM) suggested by ACI 318M-11, EC2 and CSA23.4-04 showed that the predictions are reasonable for continuous deep beams made with low and medium compressive strength. Although the equation suggested by ACI 318M-11 is very simple, its prediction is more accurate than the STM suggested by different design codes. / This research investigation was funded by the Higher Education Ministry in The Libyan Government.