Dissertations / Theses: 'Tendons (Prestressed concrete) – Evaluation'

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Tso, Karmen. "Full-range behaviour of concrete beams partially prestressed with unbonded tendons." Click to view the E-thesis via HKUTO, 2007. http://sunzi.lib.hku.hk/hkuto/record/B38225578.

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Osimani, Filippo. "The Use of Unbonded Tendons for Prestressed Concrete Bridges." Thesis, KTH, Bro- och stålbyggnad, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-37000.

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Chan, Ka-ho Enoch. "Experimental and numerical studies of concrete beams prestressed with unbonded tendons." Click to view the E-thesis via HKUTO, 2008. http://sunzi.lib.hku.hk/hkuto/record/B40988004.

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Tso, Karmen, and 曹嘉雯. "Full-range behaviour of concrete beams partially prestressed with unbonded tendons." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B38225578.

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Gauvreau, Douglas Paul. "Ultimate limit state of concrete girders prestressed with unbonded tendons /." [S.l.] : [s.n.], 1993. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=9995.

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Ariyawardena, T. M. D. Nihal. "Prestressed concrete with internal or external tendons, behaviour and analysis." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0019/NQ54766.pdf.

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Icaza, Aguirre Juan José. "Factors affecting friction losses in multi-strand post-tensioning tendons including the effect of emulsifiable oils." Full-text Adobe Acrobat (PDF) file, 2004. http://www.engr.utexas.edu/research/fsel/FSEL_reports/Thesis/Aguirre,%20Juan%20Jose%20Icaza.pdf.

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Chan, Ka-ho Enoch, and 陳家灝. "Experimental and numerical studies of concrete beams prestressed with unbonded tendons." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2008. http://hub.hku.hk/bib/B40988004.

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Chambers, John Joseph. "Parallel-lay aramid ropes for use as tendons in prestressed concrete." Thesis, Imperial College London, 1986. http://hdl.handle.net/10044/1/8327.

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Perkins, Jake. "Concrete fluidity effects on bond of prestressed tendons for lightweight bridge girders." Thesis, Manhattan, Kan. : Kansas State University, 2008. http://hdl.handle.net/2097/1080.

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Gopal, Pritiv Kumar. "Flexural behaviour of flanged concrete beams prestressed with unbonded steel or FRP tendons." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0019/MQ54454.pdf.

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ARAUJO, AELLINGTON FREIRE DE. "EXPERIMENTAL STUDY ON THE FLEXURAL STRENGTH OF CONCRETE BEAMS PRESTRESSED WITH SYNTHETIC TENDONS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1997. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=1927@1.

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COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR Nos últimos anos a protensão externa tem sido empregada tanto na recuperação e reforço de estruturas existentes quanto na concepção de novas estruturas. A protensão externa pode ser feita com cabos de aço ou com cabos sintéticos. Dentre esses, podem-se destacar os cabos Parafil, cujo núcleo é constituído de fibras kevlar. Essas fibras têm alta resistência (3700MPa), alto módulo de elasticidade (126000MPa) e excelente resistência à corrosão. Neste trabalho é feito um estudo do comportamento de vigas protendidas com cabos externos tipo Parafil, onde se identificam os principais fatores que influenciam a resistência à flexão através de um estudo paramétrico, utilizando um modelo computacional desenvolvido por Krüger (1989) e Campos (1993). Foram ensaiadas experimentalmente cinco vigas protendidas com dois cabos externos, considerando a taxa de armadura passiva e o tipo de carregamento como principais variáveis. Os resultados mostram que a taxa de armadura passiva, o tipo de carregamento, o módulo de elasticidade do reforço, a resistência do concreto e o nível de protensão inicial (protensão efetiva) têm um efeito significante sobre a resistência à flexão das vigas. Os resultados teóricos obtidos através de equações desenvolvidas para o caso de cabos de aço, mostram, de um modo geral, bons resultados para o caso de cabos Parafil. External prestressing has been used either in new structures or in the repair and rehabilitation of existing ones. The use of steel tendons has been the most usual solution, but synthetic cables have also been used over the last years. One example of these cables is a parallel-lay rope known as Parafil, which is made from the high strength (3700 MPa), high modulus (126000 MPa) and corrosion resistant fiber commercially known as Kevlar. An investigation on the behavior of beams prestressed with external Parafil tendons is conducted with the purpose of studying the flexural strength of these beams. The main variables which affect the behavior of the beams are firstly identified through a parametric analysis using an existing computational model based on the finite element method. Secondly, an experimental investigation of five simple supported beams, in which the non-prestressed reinforcement and type of loading are the main variables, is presented. The results show that the non-prestressed reinforcement, type of loading, elastic modulus of the tendons, effective prestressing force level and concrete strength have a significant affect on the flexural strength of the beams. The comparison between the experimental results and those obtained from equations developed for steel tendons, shows that these equations could also be used for beams prestressed with synthetic cables. En los últimos años la protensión externa há sido empleada tanto en la recuperación y refuerzo de extructuras existentes como en la concepción de nuevas extructuras. La protensión externa puede ser realizada con cables de acero o con cables sintéticos. Dentro de estos, se pueden destacar los cables Parafil, cuyo núcleo está constituido de fibras kevlar. Esas fibras tienen alta resistencia (3700MPa), alto módulo de elasticidad (126000MPa) y excelente resistencia a la corrosión. En este trabajo se realiza un estudio del comportamientode vigas protendidas con cables externos tipo Parafil, donde se identifican los principales factores que tienen influencia sobre la resistencia a la flexión, a través de un estudio paramétrico, utilizando un modelo computacional desarrollado por Krüger (1989) y Campos (1993). Fueron ensayadas cinco vigas protendidas con dos cables externos, considerando como principales variables la tasa de armadura pasiva y el tipo de carga. Los resultados muestran que la tasa de armadura pasiva, el tipo de carga, el módulo de elasticidad del refuerzo, la resistencia del concreto y el nível de protensión inicial (protensión efectiva) tienen un efecto significativo sobre la resistencia a la flexión de las vigas. Los resultados teóricos obtenidos a través de las ecuaciones desarrolladas para el caso de cables de acero, muestran, de un modo general, buenos resultados para el caso de cables Parafil.

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Musgrove, Ryan Ross. "Nondestructive detection of post-tensioning tendons and simulated voids in concrete specimens using thermal imaging." Online access for everyone, 2006. http://www.dissertations.wsu.edu/Thesis/Spring2006/r%5Fmusgrove%5F012506.pdf.

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FORMAGINI, SIDICLEI. "INFLUENCE OF THE CONCRETE STRENGTH ON THE BEHAVIOR OF PRESTRESSED BEAMS WITH EXTERNAL ARAMID TENDONS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1999. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=1271@1.

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COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR Este trabalho apresenta uma análise experimental de cinco vigas de concreto, simplesmente apoiadas, protendidas com cabos sintéticos externos, com o objetivo de estudar a influência da resistência do concreto na variação da força nos cabos de protensão e na resistência à flexão das vigas. A protensão das vigas foi feita com cabos sintéticos conhecidos como Parafil, com resistência a tração de 1950MPa e módulo de elasticidade de 126000MPa. A única variável considerada foi a resistência do concreto, cujo valores foram 36, 57, 73, 74 e 104MPa. O concreto das vigas com resistência de 57, 73, 74 e 104MPa foram feitos com o uso da microssílica e aditivo superplastificante, com exceção da viga com resistência de 36MPa que foi feita com concreto comum. Os resultados mostraram que a influência da resistência do concreto sobre a resistência à flexão das vigas não é tão grande. Para o aumento de 189% na resistência do concreto, houve um aumento na variação da força no cabo de apenas 13.6% e um aumento de 33% no momento de ruptura. Na comparação dos resultados experimentais com os resultados das principais normas e modelos propostos verificou-se que todos fornecem bons resultados e subestimam os valores experimentais. Na comparação dos resultados experimentais com o modelo de Campos (1993) observou-se que os valores da variação na força no cabo superestimam os valores experimentais. An experimental investigation on five concrete beams prestressed with external aramid tendons was carried out for the purpose of studying the influence of concrete on the flexural behaviour at service and ultimate loads. The beams were prestressed with Type G Parafil tendons, which are made of Kevlar 49 fibres. The strength and elastic modulus of the cables are 1950 MPa and 12600 MPa respectively. The main variable considered in the testes was the strength of the concrete with values of 36, 57, 73, 74 and 104 MPa. The results show that for an increase of 189% in the strength of the concrete, an increase of only 33% in the ultimate moment is observed. Experimental results were compared with results predicted by some Codes of Practice. This comparison shows that the theoretical models give good results. Este trabajo presenta un análisis experimental de cinco vigas de concreto, simplemente apoyadas, protendidas con cables sintéticos externos, con el objetivo de estudiar la influencia de la resistencia del concreto en la variación de la fuerza de los cables de protensión y en la resistencia a la flexión de las vigas. La protensión de las vigas fue hecha con cables sintéticos conocidos como Parafil, con resistenciaa la tracción de 1950MPa y módulo de elasticidad de 126000MPa. La única variable considerada fue la resistencia del concreto, cuyos valores fueron 36, 57, 73, 74 y 104MPa. El concreto de las vigas con resistencia de 57, 73, 74 y 104MPa fueron construidos con el uso de la microsílica y aditivo superplastificante, con excepción de la viga con resistencia de 36MPa que fue construida con concreto común. Los resultados mostraron que la influencia de la resistencia del concreto sobre la resistencia a la flexión de las vigas no es grande. Para el aumento de 189% en la resistencia del concreto, se produjo un aumento en la variación de la fuerza en el cable de apenas 13.6% y un aumento de 33% en el momento de ruptura. Comparando los resultados experimentales con los resultados de las principales normas y modelos propuestos se verificó que todos ofrecen buenos resultados y subestiman los valores experimentales. Comparando los resultados experimentales con el modelo de Campos (1993) se observó que los valores de la variación en la fuerza en el cable superestiman los valores experimentales.

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Chu, Kwong-Yiu. "A study of the deflection and strength of partially prestressed concrete beams with unbonded tendons." Thesis, University of Leeds, 1985. http://etheses.whiterose.ac.uk/184/.

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Fifteen beams with-unbonded tendons consisting of I and rectangular sections with different amounts of prestressed and non-prestressed reinforcement, were tested under short-term and sustained loading and a combination of sustained loading with intermittent short-term cyclic loading(combined loading). Two additional ordinary reinforced concrete beams were tested under combined loading for comparison purposes. Results indicated that a noticeable amount of non-recoverable residual deflection occurred due to the effect of cyclic load. The cause was believed to be non-recoverable creep strain and increased creep rate under cyclic loading. An analytical method was formulated for calculating the short-term deflection of unbonded partially prestressed beams. The deflection was calculated by integration of curvature based on the recommendations of CP110, Appendix A, with certain modification. The computed results agreed well with the experiments. The experimental deflection was also checked against the computed results according to the Model Code and the ACI Code. The former was found to be unconservative for unbonded I-section beams. The ACI Code I-effective formula might require modification of the power in order to produce consistently conservative results. Moreover, the ACI simplified formula for calculating the long-term deflection was unconservative for unbonded beams both for sustained and combined loading. The flexural strength of the test beams was greater than predicted by the CP110, Tam-Pannell and the ACI Code methods mainly due to underestimation of the tendon stress at ultimate moment. The stress in the tendon reached the 0.2% proof stress and the stress in the non-prestressed steel sometimes reached the 2.5% proof stress. The friction between the tendon and the concrete caused localised stress change and hence increased the strength of the unbonded beam significantly.

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Choo, Ching Chiaw. "Investigation of rectangular concrete columns reinforced or prestressed with fiber reinforced polymer (FRP) bars or tendons." Lexington, Ky. : [University of Kentucky Libraries], 2005. http://lib.uky.edu/ETD/ukycien2005d00258/ChooPhDDissertation%5FFinal.pdf.

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Thesis (Ph. D.)--University of Kentucky, 2005. Title from document title page (viewed on November 7, 2005). Document formatted into pages; contains xi, 139 p. : ill. Includes abstract and vita. Includes bibliographical references (p. 130-139).

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Xu, Jiangong Barnes Robert W. "Nondestructive evaluation of prestressed concrete structures by means of acoustic emissions monitoring." Auburn, Ala, 2008. http://hdl.handle.net/10415/1429.

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Roberts, James Benson Schindler Anton K. "Evaluation of self-consolidating concrete for use in prestressed girder applications." Auburn, Ala., 2005. http://repo.lib.auburn.edu/2005%20Fall/Thesis/ROBERTS_JAMES_43.pdf.

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Cuadros, Olave Gladys. "Evaluation of high strength concrete prestressed bridge girder design." Texas A&M University, 2003. http://hdl.handle.net/1969/208.

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Dunbeck, Jennifer. "Evaluation of high strength lightweight concrete precast, prestressed bridge girders." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/28091.

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Davis, Brent M. "Evaluation of prestress losses in an innovative prestressed precast pavement system." Diss., Columbia, Mo. : University of Missouri-Columbia, 2006. http://hdl.handle.net/10355/4516.

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Thesis (M.S.) University of Missouri-Columbia, 2006. The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on August 22, 2007) Includes bibliographical references.

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NACHT, PEDRO KAJ KJELLERUP. "INTERACTIVE GRAPHICS TOOL FOR SERVICEABILITY LIMIT STATE STRESS CHECK OF PRESTRESSED CONCRETE BEAMS WITH POST-TENSIONED BONDED TENDONS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2015. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=27386@1.

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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO Este trabalho apresenta o desenvolvimento de uma ferramenta computacional gráfico-interativa para a verificação de vigas de concreto protendido com pós-tração aderente ao estado limite de serviço, de acordo com a norma brasileira NBR 6118:2014. A ferramenta é uma extensão (addin) para o Autodesk Robot Structural Analysis Professional , que serve como plataforma de modelagem estrutural. A partir de dados fornecidos pelo usuário através de uma interface gráfica, o programa desenvolvido calcula todas as perdas de protensão que ocorrem ao longo da vida-útil da estrutura, assim como os carregamentos equivalentes à protensão durante este período. O trabalho apresenta os métodos de cálculo tradicionais das perdas imediatas e diferidas, obtidos da NBR 6118, e as modificações que tiveram que ser feitas para permitir um cálculo incremental. Exemplos de utilização do programa e dos cálculos necessários também são apresentados e comprovam, pelos bons resultados obtidos, o acerto na escolha da metodologia escolhida. Como resultado, a ferramenta apresenta duas saídas: uma planilha contendo os esforços e as tensões atuantes na viga ao longo de sua vida-útil e verificações destes valores em relação aos limites estabelecidos para o estado limite de serviço; e o modelo estrutural no Robot apresenta os carregamentos equivalentes da protensão. O usuário pode então adotar estes carregamentos em demais cálculos da estrutura, enquanto a planilha pode ser utilizada para verificar com facilidade se a protensão atende às condições de serviço. This work presents the development of an interactive graphics computational tool for the verification of prestressed concrete beams with posttensioned bonded tendons to the serviceability limit state stress check according to the Brazilian code NBR 6118:2014. The tool is an add-in for Autodesk Robot Structural Analysis Professionalr, which serves as a structural modeling platform. With data supplied by the user through a graphics user interface, the program here developed calculates all relevant prestress losses that occur throughout the structure s life-cycle, along with the prestressing s equivalent loads during this period. The traditional calculation methods, obtained in the NBR 6118, are presented along with the modifications which had to be implemented in order to allow for incremental loss calculations. Usage examples and the necessary calculations are presented and, through the results obtained, validate the adopted methodology. As results, the program presents two outputs: a spreadsheet containing the resultant forces and stresses and a check of these values with respect to the permissible stresses in the serviceability limit state; and the Robot model presents the prestress equivalent loads. The user may then use these loads in additional calculations. The spreadsheet may be used to easily check if the prestress is sufficient with respect to serviceability conditions.

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Camino, Trujillo Santiago J. "Analytical Evaluation of Damaged Prestressed Concrete Box Beams Bridge Girders." Ohio University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1282326000.

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Luckenbill, Grant C. Gopalaratnam Vellore S. "Evaluation of the service performance of an innovative precast prestressed concrete pavement." Diss., Columbia, Mo. : University of Missouri--Columbia, 2009. http://hdl.handle.net/10355/6473.

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Title from PDF of title page (University of Missouri--Columbia, viewed on Feb 18, 2010). The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Thesis advisor: Dr. Vellore S. Gopalaratnam. Includes bibliographical references.

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Tasnimi, A. A. "Prediction of forces within prestressed sections : The behavior of simply supported prestressed concrete beams with boned and unbonded tendons predicted by mathematical model and investigated by testing to destruction using two point load." Thesis, University of Bradford, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384298.

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Hodges, Hunter Thomas. "Top Strand Effect and Evaluation of Effective Prestress in Prestressed Concrete Beams." Thesis, Virginia Tech, 2006. http://hdl.handle.net/10919/36300.

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The first objective of this thesis was to assess the effect of casting orientation on bond strength in pretensioned prestressed concrete members. The "top strand effect" was evaluated through transfer and development length tests of prestressed concrete beams. Eight beams were cast with normal orientation, while four beams were cast with inverted orientation so that a significant depth of fresh concrete was placed below prestressing strands. Discrete transfer lengths were determined at the ends of each beam by measuring concrete surface strains. Inverted casting orientation caused an average 70 percent increase in transfer length. Some transfer lengths in beams with inverted casting orientation exceed current ACI and AASHTO code provisions. All measured transfer lengths were less than 90 strand diameters (45 in. for 0.5 in. diameter strands). Ranges of development length were determined through iterative load testing. The top strand effect on development length was more qualitative than quantitative. Ranges of development length in normal beams were conservatively less than code provisions. Ranges of development length in beams with inverted casting orientation were much closer to and sometimes exceeded code provisions. It is recommended that ACI and AASHTO code provisions for the development length of prestressing strand be modified to include the same magnification factors that are specified for the development length of deformed bars with twelve or more inches of fresh concrete placed below. The second objective of this thesis was to compare experimentally measured prestress losses to theoretical calculations. Theoretical prestress losses were calculated according to PCI and AASHTO Refined methods. These methods produced similar results. Prestress losses were experimentally measured by vibrating wire gages and flexural load testing. Vibrating wire gages were used to monitor internal concrete strains. Two methods were used to reduce vibrating wire gage data: an upper/lower bound method and a basic method. The upper/lower bound method produced distorted data that was unreasonable in some cases. The basic method was more reasonable, but resulted in some prestress loss measurements that were greater than theoretical predictions. Flexural load testing was used to back calculate prestress losses from crack initiation and crack reopening loads. Prestress losses measured by crack initiation loads were generally greater than theoretical values. Losses measured by crack reopening loads were distorted. The distortion was attributed to difficulty in isolation of the correct crack reopening load. Large measurements of prestress losses by the basic vibrating wire gage and crack initiation methods suggested that losses occurred between the time when concrete was poured and prestress transfer occurred. Such losses are not accounted for in current code provisions. More research is recommended to determine the magnitude of these additional losses and their effect on design. Master of Science

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Grotheer, Sarah Jo. "Evaluation of lightweight concrete mixtures for bridge deck and prestressed bridge girder applications." Thesis, Manhattan, Kan. : Kansas State University, 2008. http://hdl.handle.net/2097/768.

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Filho, Fernando Menezes de Almeida. "Estruturas de pisos de edifícios com a utilização de cordoalhas engraxadas." Universidade de São Paulo, 2002. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-26052006-153328/.

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O presente trabalho aborda a utilização da protensão não aderente em edifícios residenciais e comerciais de concreto, focando os aspectos referentes às soluções com protensão aderente e não aderente e em concreto armado, para o consumo de materiais, notadamente: concreto, fôrmas e armaduras. São considerados três diferentes sistemas estruturais, sendo estes: laje plana maciça apoiada sobre pilares; laje plana nervurada apoiada sobre pilares e laje nervurada apoiada em vigas faixa protendidas sobre pilares. São apresentados estudos destes casos com a utilização da ferramenta computacional de análise estrutural TQS, a qual é baseada na análise por grelha. São comparados os índices de consumo de materiais para os dois referidos sistemas de protensão, discutindo os limites de sua utilização. Como resultados, o estudo fornece conclusões satisfatórias para utilização da protensão, tanto aderente quanto não aderente, em relação ao concreto armado. Ainda, o sistema de protensão aderente mostrou-se ligeiramente mais econômico, do ponto de vista de consumo de materiais, porém, é um sistema com produtividade inferior às soluções com protensão não aderente, tornando esta última solução, a mais adotada no cotidiano dos escritórios de cálculo de engenharia civil dentre as citadas The present work deals the use of the prestressed unbonded tendons in residential and commercial concrete buildings, pointing out aspects to the application with bonded and unbonded prestressing and reinforced concrete, regarding the consumption such as concrete, molds and reinforcing steel. Three different structural systems are considered: flat plate and columns; waffle slab and columns and waffle slab (non prestressed) in prestressed strip beams supported by columns. Case studies are presented with the use of the software of structural analysis TQS, which is based on the grillage analogy method. The consumption of materials is compared for the two referred prestressing systems, discussing the limits of their application. Based on the developed analyses, the study supplies satisfactory conclusions for use of the prestressing systems (bonded and unbonded), compared to reinforced concrete systems. With relation to the consumption of materials, the use of bonded tendons is a bit more cost effective, however, with smaller productivity than tendons with prestressed unbonded tendons, being the last one the more usual prestressing systems. Still, the system of prestressed bonded tendons was shown more economical, of the point of view of materials consumption, however, it is a system with inferior productivity to the solutions with prestressed unbonded tendons adopted in civil engineering offices nowadays

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Moser, Robert David. "High-strength stainless steels for corrosion mitigation in prestressed concrete: development and evaluation." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/41083.

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The use of stainless steel alloys in reinforced concrete structures has shown great success in mitigating corrosion in even the most severe of exposures. However, the use of high-strength stainless steels (HSSSs) for corrosion mitigation in prestressed concrete (PSC) structures has received limited attention. To address these deficiencies in knowledge, an experimental study was conducted to investigate the feasibility of using HSSSs for corrosion mitigation in PSC. The study examined mechanical behavior, corrosion resistance, and techniques for the production of HSSS prestressing strands. Stainless steel grades 304, 316, 2101, 2205, 2304, and 17-7 along with a 1080 prestressing steel control were included in the study. Tensile strengths of 1250 to 1550 MPa (181 to 225 ksi) were achieved in the cold-drawn HSSSs. 1000 hr stress relaxation of all candidate HSSSs was predicted to be between 6 and 8 % based on the results of 200 hr tests conducted at 70 % of the ultimate tensile strength. Residual stresses due to the cold drawing had a significant influence on stress vs. strain behavior and stress relaxation. Electrochemical corrosion testing found that in solutions simulating alkaline concrete, all HSSSs showed exceptional corrosion resistance at chloride (Cl-) concentrations from zero to 0.25 M. However, when exposed to solutions simulating carbonated concrete, corrosion resistance was reduced and the only HSSSs with acceptable corrosion resistance were duplex grades 2205 and 2304, with 2205 resistant to corrosion initiation at Cl- concentrations up to 1.0 M (twice that in seawater). Based on these results, duplex grades 2205 and 2304 were identified as optimal HSSSs and were included in additional studies which found that: (1) 2304 is susceptible to corrosion when tested in a stranded geometry, (2) 2205 and 2304 are not susceptible to stress corrosion cracking, and (3) 2205 and 2304 are susceptible to hydrogen embrittlement. Efforts focused on the production of 2205 and 2304 prestressing strands showed that they could be produced as strands using existing ASTM A416 prestressing strand production facilities. Due to the ferromagnetic properties of 2205 and 2304, a low-relaxation heat treatment was found to be a viable option to reduce stress relaxation and improve mechanical properties. The overall conclusion of the study was that HSSSs, especially duplex grades 2205 and 2304, show excellent promise to mitigate corrosion if utilized as prestressing reinforcement in PSC structures exposed to severe marine environments.

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Fernandez, Joseph Rogelio. "Stress Corrosion Cracking Evaluation of Candidate High Strength Stainless Steels for Prestressed Concrete." Scholar Commons, 2011. http://scholarcommons.usf.edu/etd/3102.

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Prestressed concrete piles are commonly used to support over-water highway bridges in marine environments. The reinforcing steel within will ultimately be degraded via corrosion damage due to the penetration of chloride ions from sea water. The service life of these structures is, in part, dictated by the time required to diffuse chloride ions through the concrete cover and subsequently corrode the steel. Therefore, by slowing the rate of diffusion or increasing the chloride threshold of the steel (or both) an increased service life can be expected. This thesis focuses on the latter whereby stainless steel reinforcing alternatives were investigated to elevate the chloride threshold before corrosion begins. The designation "stainless" steel implies corrosion resistance. However, corrosion resistance in itself is not a sufficient condition to make it a suitable alternative for prestressed concrete applications. In this study, the corrosion susceptibility of stainless steel alloys was scrutinized with the understanding that high strength stainless steels are vulnerable to stress corrosion cracking (SCC). This investigation screened three candidate alloys that span the norms of stainless steel compositions: a common austenitic stainless steel with high nickel content (316L), a less common austenitic stainless steel with low nickel but high manganese (XM 29), and a duplex stainless steel with high chromium and an additional constituent, molybdenum (2205). Each alloy was subjected to two stress conditions imposed by varied mechanical fixtures then subjected to various forms of high chloride concentrations. The pH of these conditions was also varied and in one case simulated the high pH common to concrete pore water solutions. Elevated temperatures were used to accelerate the effects of these exposures. Results of Phase 1 showed that for exposure at 135oC (275oF) cracking of alloys 316 L and 2205 occurred after 1 hour while XM29 experience cracking after 24 hours. At 90oC (194oF) alloy 316L cracked after 4 hours; XM29 did not crack after 96 hours while 2205 did crack after 96 hours. The results were interpreted with an Arrhenius relationship between time to cracking and test temperature to extrapolate toward the anticipated service regime. Results of Phase 2 showed that SCC was less likely to initiate in high pH conditions than in low pH conditions at typical marine environment temperatures and chloride concentration. In these limited tests the SCC performance of XM29 was better relative to that of the other two alloys.

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Jost, Daniel Trevisan. "Análise de peças fletidas com protensão não aderente pelo método dos elementos finitos." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2006. http://hdl.handle.net/10183/11037.

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Estruturas com protensão não aderente estão sendo utilizadas como uma alternativa na tecnologia de projeto e execução de edifícios. Este trabalho apresenta a análise numérica de estruturas com protensão não aderente. Para este fim, foi desenvolvido um programa computacional onde implementou-se um modelo não linear físico e geométrico através do método dos elementos finitos. O comportamento dos materiais é descrito por um modelo elasto-viscoplástico. No concreto, são utilizados elementos finitos isoparamétricos tridimensionais. Para representar o seu comportamento após a fissuração é utilizado o modelo de fissuras distribuídas. As armaduras são incluídas através do modelo incorporado, utilizando-se de elementos unidimensionais isoparamétricos.As armaduras passivas são consideradas como uma linha de material mais rígido no interior do elemento de concreto, existindo uma aderência perfeita entre o concreto e o aço. Nas armaduras não aderentes, é considerada a compatibilidade de deslocamentos entre os materiais apenas nas ancoragens, sendo que a armadura pode movimentar-se livremente no interior do concreto. O modelo não linear geométrico, utilizado para o concreto e para a armadura, foi desenvolvido com base na formulação Lagrangeana Total, considerando grandes deslocamentos e pequenas deformações. Para verificar a precisão do modelo computacional, compararam-se resultados numéricos com valores experimentais disponíveis na literatura. Unbonded prestressed concrete structures have been increasingly used as an alternative in the technology of design and construction of buildings. This work presents a numerical analysis of unbonded prestressed concrete structures. To accomplish this, a computational program has been developed in which a physical and geometrical nonlinear model was implemented through the finite element method. Materials behavior has been described through an elasto-viscoplastic model. In the concrete, a threedimensional isoparametric finite element has been used. To represent its behavior after cracking, the smeared cracking model has been used to. The prestressing tendons and reinforcement have been included according with the embedded model approach by the use of one-dimensional isoparametric elements. The reinforcement has been considered in the model as a line of a stiffer material inside the concrete element, with a perfect bonding between concrete and steel. As for the unbonded tendons, displacement compatibility between materials has been considered only at the anchorages, but they are allowed to move freely along their length inside the concrete. The geometric nonlinear model that has been used for the concrete, reinforcement and tendons has been developed according to the Total Lagrangean formulation, considering large displacements and small strains. In order to evaluate the accuracy of the computational model, numerical results have been compared with experimental values available in the literature.

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Gamble, Joanne M. "Field evaluation of calcium nitrite and chloride in Ohio prestressed concrete box beam bridge girders." Ohio : Ohio University, 1996. http://www.ohiolink.edu/etd/view.cgi?ohiou1178652761.

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Lammert, Kimberly. "Structural evaluation of impact damaged prestressed concrete I girders repaired with fiber reinforced polymer (FRP) materials." [Gainesville, Fla.] : University of Florida, 2003. http://purl.fcla.edu/fcla/etd/UFE0001119.

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Greenwood, Steven Michael. "Analytical performance evaluation of hollow prestressed piles and pile-cap connections in the I-5 Ravenna Bridge." Pullman, Wash. : Washington State University, 2008. http://www.dissertations.wsu.edu/Thesis/Fall2008/S_Greenwood_012608.pdf.

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Thesis (M.S. in civil engineering)--Washington State University, December 2008. Title from PDF title page (viewed on Apr. 8, 2009). "Department of Civil and Environmental Engineering." Includes bibliographical references (p. 136-140).

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Lazzari, Paula Manica. "Implementação de rotinas computacionais para o projeto automático de peças em concreto com protensão aderente e não aderente." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2011. http://hdl.handle.net/10183/36374.

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Este trabalho versa sobre o desenvolvimento de rotinas computacionais para o projeto automático de estruturas de concreto submetidas à protensão aderente e não aderente, conforme recomendações das normas brasileira [NBR6118:2007] e francesa [Règles BPEL 91]. A justificativa da realização deste trabalho vem da crescente utilização da protensão no Brasil, devido principalmente a suas vantagens construtivas, à redução na incidência de fissuras e na dimensão das peças com o emprego eficiente de materiais de maior resistência. Visando contribuir para o desenvolvimento científico nacional, o presente trabalho dá continuidade a uma linha de pesquisa que vem sendo desenvolvida no Programa de Pós- Graduação em Engenharia Civil – PPGEC/UFRGS, a qual foi iniciada com a implementação de um modelo numérico, baseado na formulação do elemento finito do tipo híbrido para pórticos planos, que faz a análise quanto à flexão de seções com protensão aderente e não aderente. A partir deste elemento finito, torna-se possível a utilização de elementos longos, de maneira que um único elemento finito possa ser utilizado para um vão de viga ou pilar, reduzindo, assim, o esforço computacional. O modelo numérico considera a não linearidade geométrica, carregamentos cíclicos e construção composta, levando em conta a concretagem por fases. Relações constitutivas já consolidadas na literatura são empregadas para os materiais, sendo que a cadeia de Maxwell é utilizada para representar o comportamento reológico do concreto e do aço de protensão, respeitando as características de cada material. Realizou-se, ainda, um estudo das variáveis necessárias na implementação do modelo numérico a fim de desenvolver uma interface gráfica amigável com a ajuda do software Microsoft Visual Basic 2008 Express Edition, disponível gratuitamente na internet, facilitando, desta forma, a entrada de dados. As rotinas computacionais implementadas efetuam a verificação dos estados limites de serviço e últimos, complementando o modelo numérico original. São consideradas as situações de protensão completa, limitada e parcial e verificados conforme cada caso, os estados limites de descompressão, de formação e de abertura das fissuras, além dos estados limites últimos finais, no ato da protensão e a verificação do esforço cortante. São apresentadas comparações entre situações de projeto conforme as normas brasileira e francesa, analisando de forma crítica os resultados obtidos. De um modo geral, observou-se que as verificações feitas pela norma francesa apresentaram resultados mais conservadores. Ao longo deste trabalho, buscou-se, como objetivo principal, tornar o programa computacional operacional para a realização de projetos. This work presents the development of computational algorithms for the automatic design of concrete structures subjected to bonded and unbonded prestressing, according to the Brazilian [NBR6118:2007] and French [Règles BPEL 91] code specifications. The study is justified by the increased use of prestressing in Brazil, due to its many constructive advantages, like reduction in crack incidence and decrease in section dimensions, with the efficient use of higher resistance materials. It is part of a major research developed in the Graduate Program in Civil Engineering - PPGEC/UFRGS, started with the implementation of a numerical model based on the formulation of a hybrid type finite element for prestressed plane frames. Such model, makes possible the use long elements, so that a single finite element can be used for modeling a beam or column, therefore improving computational efficiency. The numerical model considers geometric nonlinearity, cyclic loading and composite construction, allowing different constructive stages. Well established constitutive relations are used for representing material behavior and the Maxwell chain model is used for both concrete and prestressing steel time-dependent responses. A study on the variables needed to implement the numerical model was performed, in order to develop a friendly graphical interface, with the help of Microsoft Visual Basic 2008 Express Edition, a free software that facilitates data acquisition. The implemented computational algorithm performs the verification of the Serviceability Limit States and the Ultimate Limit State, with a view to complementing the original numerical model. Full, partial and limited prestressing situations are considered and checked and, in each case, the Limit State of Decompression, the Limit State of Cracking, the Ultimate Limit State, the final act of prestressing and the Shear Strength are verified. Comparison between design situations according to the Brazilian and French code specifications are presented. In general, it was observed that verifications of the French code were more conservative. This work was focused on the main objective to make the computer program operational for structural design.

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Fernandes, Bertrand. "Development of a Magnetic Field Sensor System for Nondestructive Evaluation of Reinforcing Steel in Prestressed Concrete Bridge Members." University of Toledo / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1352760825.

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Nadia, Binti Kamaruddin. "Durability and Seismic Resistance of a 60-Year Old Precast Prestressed Concrete Building Based on Field Inspections and Laboratory Testings." Kyoto University, 2018. http://hdl.handle.net/2433/235085.

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BOLDUC, MATTHEW W. "USE OF CARBON FIBER REINFORCED POLYMER PLATES FOR REPAIR OR RETROFIT OF PRESTRESSED AND REINFORCED CONCRETE GIRDERS." University of Cincinnati / OhioLINK, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1046870127.

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Arginhan, Oktay. "Reliability Based Safety Level Evaluation Of Turkish Type Precast Prestressed Concrete Bridge Girders Designed In Accordance With The Load And Resistance Factor Desing Method." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612723/index.pdf.

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The main aim of the present study is to evaluate the safety level of Turkish type precast prestressed concrete bridge girders designed according to American Association of State Highway and Transportation Officials Load and Resistance Factor Design (AASHTO LRFD) based on reliability theory. Span lengths varying from 25 m to 40 m are considered. Two types of design truck loading models are taken into account: H30S24-current design live load of Turkey and HL93-design live load model of AASHTO LRFD. The statistical parameters of both load and resistance components are estimated from local data and published data in the literature. The bias factors and coefficient of variation of live load are estimated by extrapolation of cumulative distribution functions of maximum span moments of truck survey data (Axle Weight Studies) that is gathered from the Division of Transportation and Cost Studies of the General Directorate of Highways of Turkey. The uncertainties associated with C40 class concrete and prestressing strands are evaluated by the test data of local manufacturers. The girders are designed according to the requirements of both Service III and Strength I limit states. The required number of strands is calculated and compared. Increasing research in the field of bridge evaluation based on structural reliability justifies the consideration of reliability index as the primary measure of safety of bridges. The reliability indexes are calculated by different methods for both Strength I and Service III limit states. The reliability level of typical girders of Turkey is compared with those of others countries. Different load and resistance factors are intended to achieve the selected target reliability levels. For the studied cases, a set of load factors corresponding to different levels of reliability index is suggested for the two models of truck design loads. Analysis with Turkish type truck models results in higher reliability index compared to the USA type truck model for the investigated span lengths

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Fernandes, Bertrand. "Nondestructive Evaluation of Deteriorated Prestressing Strands Using Magnetic Field Induction." University of Toledo / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1271432554.

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Kovalíková, Mária. "Statické zajištění kostela v Ludslavicích." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2015. http://www.nusl.cz/ntk/nusl-227609.

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This thesis is drafting static protection church horizontal pretension, especially at the level of foundations and walls. Furthermore, the design of a new increase the stiffness of reinforced concrete towers and other prestress. The role was also producing construction drawings for the design of static security.

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Němec, Petr. "Projekt zastřešení výstavní haly." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2013. http://www.nusl.cz/ntk/nusl-226442.

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The Diploma’s thesis is focused on the design of selected parts of reinforced concrete exhibition hall (prestressed concrete purlin, prestressed concrete girder, reinforced concrete column, reinforced concrete footing, post-tensioned concrete girders). The load calculation (the self weight, the permanent load, the wind load, the snow load and imposed load), the design and the review of selected reinforced concrete items and the drawing documentation are included in this thesis.

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Výpustek, Libor. "Průzkum a hodnocení mostu na dálnici D2." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2013. http://www.nusl.cz/ntk/nusl-225738.

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

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Salas, Pereira Rubén Mario. "Accelerated corrosion testing, evaluation and durability design of bonded post-tensioned concrete tendons." 2003. http://wwwlib.umi.com/cr/utexas/fullcit?p3118069.

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Lee, Jun Ki 1975. "Evaluation of external post-tensioned tendons using vibration signatures." Thesis, 2007. http://hdl.handle.net/2152/3490.

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Recent findings regarding corrosion of post-tensioned bridges have highlighted the urgent need to develop reliable methods to predict the behavior of the structural system after damage has occurred and inspection techniques to assess the condition of the structure. Corrosion in strands is undesirable in that it often progresses without visual signs of distress, but may cause a brittle failure. To complicate the inspection, access to the strands for visual inspection is usually blocked by the concrete cross section. To date, significant efforts have been taken to improve the durability of the post-tensioned bridges. However, the behavior of the post-tensioned bridges with corrosion damage is not clearly understood and the currently available inspection techniques tend to provide only limited information about the nature and extent of the damage. The research project discussed in this dissertation was developed is to evaluate the feasibility of using the vibration technique to detect and estimate the extent of damage in an external tendon due to corrosion. To accomplish this goal, damage was induced in five specimens, which were monitored periodically to correlate the measured changes in the frequency response to the level of damage. The induced damage simulated the degradation of a post-tensioned structure from corrosion. This dissertation describes the experimental program and the numerical scheme used to estimate the condition of the specimens. Three types of specimens were tested during the experimental phase of the research: individual strands, cables specimens, and external tendons. A series of tension tests of individual strands were conducted to investigate changes in the uniaxial behavior after damage was induced. Simulated damage included uniform corrosion of the strand, mechanical wire cuts, and an initial defect in one wire. Three cable specimens and one tendon specimen were subjected to fatigue loading. The loading was selected to simulate the loss of cross-sectional area in the strands, and also caused grout damage. The frequency response of the specimens was recorded periodically during the fatigue tests and acoustic sensors were used to detect the occurrence of wire breaks. A second tendon specimen was exposed to an acid solution to simulate the hydrogen induced cracking in the strand at three different locations along the length of the specimen. A number of wires fractured during the exposure test and damage was inspected visually. Natural frequencies were also measured periodically. The residual prestressing force in of the specimens was extracted from the measured natural frequencies. The stiff string model was used to determine optimum values of tension and flexural stiffness from the frequency response. The numerical results from this optimization demonstrated the feasibility of using the vibration technique as a nondestructive testing method for external tendons.

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Salas, Pereira Rubén Mario 1968. "Accelerated corrosion testing, evaluation and durability design of bonded post-tensioned concrete tendons." 2003. http://hdl.handle.net/2152/12506.

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Noshiravani, Talayeh. "Shear resistance of concrete girders prestressed with unbonded tendons." 2007. http://link.library.utoronto.ca/eir/EIRdetail.cfm?Resources__ID=452800&T=F.

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Abdelrahman, Amr A. "Serviceability of concrete beams prestressed by fibre reinforced plastic tendons." 1996. http://hdl.handle.net/1993/19077.

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Chen, Pei-lin, and 陳佩琳. "The Reduction for Use of Prestressed Tendons in Design of Precast Prestressed Concrete Bridge Girders Made Continuous." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/28633359418629142781.

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Amato, Lucio Roger. "CFRP Tendons For The Repair Of Post-Tensioned, Ubonded Concrete Buildings." Thesis, 2009. http://hdl.handle.net/1974/1775.

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The deterioration of prestressed concrete structures due to corrosion is a costly problem. This problem is accelerated in cold weather climates where de-icing salts are used. These salts accelerate the corrosion of the steel tendons greatly reducing the service life of the structures and leading to constant costly repairs. Recent research has shown composite materials such as Fibre Reinforced Polymers (FRP) to be suitable alternatives to steel, providing similar strength without being susceptible to electrochemical corrosion. Carbon FRP in particular has great promise for prestressed applications, showing resistance to corrosion in environments that might be encountered in concrete and experiencing less relaxation than steel. This thesis outlines the testing and implementation of a post-tensioned system that uses CFRP tendons to replace corroded, unbonded post-tensioned steel tendons. This system was then implemented in a parking garage in downtown Toronto. To the author’s knowledge, this is the first example of an unbonded, post-tensioned tendon replacement using FRP tendons. The system used split wedge anchors designed specifically for CFRP tendons at the University of Waterloo. The dead end was anchored by directly bonding the tendon to the concrete slab. Overall, the system was shown to work and provide a durable solution for unbonded post-tensioning systems. The CFRP tendon was successfully inserted in the opening left by the removal of the corroded tendon and stressed. It was found that the current anchorage configuration experienced large load losses of up to 60 % during the transfer. Changing the orientation of the anchor was found to reduce the load lost to a range of 1 % to 9 %. Thesis (Master, Civil Engineering) -- Queen's University, 2009-04-09 15:30:59.865

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