Este trabalho de doutorado versa sobre a simulação numérica das etapas construtivas de pontes estaiadas através do método dos elementos finitos, utilizando a plataforma ANSYS, versão 14.5. A justificativa da realização deste trabalho vem da crescente utilização deste tipo de estrutura de ponte no Brasil, devido, principalmente, ao seu bom comportamento estrutural e pela possibilidade de uso de uma estrutura mais leve, esbelta e econômica. Inicialmente, foi feita uma pesquisa abrangente sobre os componentes estruturais e concepções de projetos mais utilizados. Em seguida, estudaram-se as relações constitutivas de cada material constituinte, a fim de melhor representá-los na simulação numérica. Para a representação das equações constitutivas do concreto, implementou-se um novo modelo de material visco-elastoplástico com fissuração, com a ajuda da ferramenta de customização UPF (User Programmable Features), onde foram adicionadas novas sub-rotinas ao programa principal em linguagem FORTRAN. Como o objetivo final desta tese era trabalhar com análise estrutural das etapas construtivas de pontes estaiadas, envolvendo um número muito grande de elementos finitos, a implementação deste novo modelo possibilitou a utilização de elementos tridimensionais quadráticos de 20 nós (SOLID186) com armadura incorporada (REINF264), tornando a solução do problema mais rápida e eficaz. A fim de validar as sub-rotinas acrescentadas ao sistema, foram simuladas dezesseis vigas em concreto armado, ensaiadas por Leonhardt e Walther (1962) e por Bresler e Scordelis (1963), e uma viga segmentada com protensão externa, ensaiada por Aparicio et al (2002). A comparação de resultados das análises numéricas e experimentais mostraram boa aproximação. Após a validação das sub-rotinas, foi modelada numericamente a Ponte do Saber, localizada na cidade do Rio de Janeiro, seguindo fielmente as etapas construtivas adotadas na construção da ponte. A partir dos dados de monitoramento desta ponte, durante a fase executiva, foi possível comparar os valores obtidos no modelo numérico com as informações coletadas em campo, obtendo-se bons resultados. / This doctoral thesis presents the numerical simulation of the construction stages of cable-stayed bridges using the finite element method, through the ANSYS software, version 14.5. This work is justified by the increasing use of such structures in Brazil, mainly due to its good structural behavior and the possibility of using a lighter, slender and economic structure. Initially, it presents the results of a research about the structural components and the commonly used design concepts. Then, the constitutive relations of each constituent material were studied, in order to best represent them in the numerical simulation. For the representation of the constitutive equations of concrete, it was implemented a new model of visco-elastoplastic material with cracking. That was made with the help of the customization tool UPF (User Programmable Features), where new subroutines were added to the main program in FORTRAN language. The final goal of this thesis is to work with structural analysis of the construction stages of cable-stayed bridges, involving a very large number of finite elements. Therefore, the implementation of this new model enabled the use of three-dimensional quadratic elements of 20 nodes (SOLID186) with embedded reinforcement (REINF264), making the solution of the problem faster and more effective. In order to validate the subroutines added to the system, sixteen reinforced concrete beams tested by Leonhardt and Walther (1962) and by Bresler and Scordelis (1963), and a segmental beam with external prestressing, tested by Aparicio et al (2002) were simulated. The comparison of results of numerical and experimental analyzes showed good approximation. After validation of the subroutines, it was numerically modeled the Saber Bridge, located in the city of Rio de Janeiro, following exactly the constructive steps taken in the construction of the bridge. Based on the monitoring data of the bridge during the construction phase, it was possible to compare the values obtained from the numerical model with the information collected in the field, obtaining good results.

A novel type of precast, prestressed concrete structural element is being implemented in load-bearing systems in buildings. These structural elements combine the use of high-performance, self-consolidating concrete (HPSCC) and non-corroding carbon fibre reinforced polymer (CFRP) prestressing tendons; this produces highly optimized, slender structural elements with excellent serviceability and (presumed) extended service lives. More widely, the use of new construction techniques, innovative materials, and ground-breaking designs is increasingly commonplace in today's rapidly evolving building construction industry. However, the performance of these and other structural elements in fire is in general not well known and must be understood before these can be used with confidence in load-bearing applications where structural fire resistance is a concern. Structural fire testing has traditionally relied on the use of the standard fire resistance test (i.e. furnace test) for assuring regulatory compliance of structural elements and assemblies, and in many cases also for developing the scientific understanding of structural response to fire. Conceived in the early 1900s and fundamentally unchanged since then, the standard testing procedure is characterized by its high cost and low repeatability. A novel test method, the Heat-Transfer Rate Inducing System (H-TRIS), resulting from a mental shift associated with controlling the thermal exposure not by temperature (e.g. temperature measured by thermocouples) but rather by the time-history of incident heat flux, was conceived, developed, and validated within the scope of the work presented in this thesis. H-TRIS allows for experimental studies to be carried out with high repeatability, imposing rationally quantifiable thermal exposure, all at low economic and temporal cost. The research presented in this thesis fundamentally seeks to examine and understand the behaviour of CFRP prestressed HPSCC structural elements in fire, with emphasis placed on undesired 'premature' failure mechanisms linked to the occurrence of heat-induced concrete spalling and/or loss of bond between the pretensioned CFRP tendons and the concrete. Results from fire resistance tests presented herein show that, although compliant with testing standards, temperature distributions inside furnaces (5 to 10% deviation) appear to influence the occurrence of heat-induced concrete spalling for specimens tested simultaneously during a single test; fair comparison of test results is therefore questionable if thermal exposure variability is not explicitly considered. In line with the aims of the research presented in this thesis, H-TRIS is used to carry out multiple comprehensive studies on the occurrence of concrete spalling and bond behaviour of CFRP tendons; imposing a quantified, reproducible and rational thermal exposure. Test results led to the conclusion that a "one size fits all" approach for mitigating the risk of heat-induced concrete spalling (e.g. prescribed dose of polypropylene (PP) fibres included in fresh concrete), appears to be ineffective and inappropriate in some of the conditions examined. This work demonstrates that PP fibre cross section and individual fibre length can have an influence on the risk of spalling for the HPSCC mixes tested herein. The testing presented herein has convincingly shown, for the first time using multiple repeated tests under tightly controlled thermal and mechanical conditions, that spalling depends not only on the thermal gradients in concrete during heating but also on the size and restraint conditions of the tested specimen. Furthermore, observations from large scale standard fire resistance tests showed that loss of bond strength of pretensioned CFRP tendons occurred at a 'critical' temperature of the tendons in the heated region, irrespective of the temperature of the tendons at the prestress transfer length, in unheated overhangs. This contradicts conventional wisdom for the structural fire safety design of concrete elements pretensioned with CFRP, in which a minimum unheated overhang is generally prescribed. Overall, the research studies presented in this thesis showed that a rational and practical understanding of the behaviour of CFRP prestressed HPSCC structural elements during real fires is unlikely to be achieved only by performing additional standard fire resistance tests. Hence, H-TRIS presents an opportunity to help promote an industry-wide move away from the contemporary pass/fail and costly furnace testing environment. Recommendations for further research to achieve the above goal are provided.

Este trabalho apresenta os resultados das investigações teórica e experimental sobre a aderência de cordoalhas pré-tracionadas, em concretos de alta resistência com e sem fibras de aço. Foram utilizadas cordoalhas de sete fios com &#934p 12,7 mm e fibras de aço curtas, com ganchos nas extremidades (DRAMIX) e fator de forma 1/d=45. Foram realizados dois tipos de ensaios: arrancamento e flexão em viga. Os parâmetros estudados foram: comprimento de ancoragem (5&#934p, 7&#934p e 15&#934p), volume de fibra (zero, 40 kg/m3 e 60 kg/m3 e grau de protensão (zero e 0,8fptk). O concreto apresentou resistências à compressão de 50 MPa no momento da transferência da protensão e 68 MPa na data de ensaio, aproximadamente. Os resultados dos dois tipos de ensaio foram analisados e comparados com as prescrições normativas da NBR 6118 (2001), da FIB Bulletin 1 (1999) e do ACI 318 (2002), onde verificou-se que as prescrições se encontram a favor da segurança. A conclusão principal resultante desta pesquisa foi que a utilização de fibras com 40 kg/\'m3 por metro quadrado não influi na aderência. Já para um volume de fibra de 60 kg/\'m3 por metro quadrado há um ganho de aproximadamente 28% na aderência, em relação aos concretos sem fibras de aço, nos ensaios de arrancamento. Para as vigas, não houve ganho de aderência para os volumes de fibra utilizados, nem na determinação do comprimento de transferência, nem na do comprimento de ancoragem necessário. / This study presents the results of a theoretical and an experimental investigation of the bond of pretensioned strands embedded in plain and steel fiber reinforced high strength concrete. There were used seven wires strands with 12,7 mm diameter and short hooked steel fibers with an aspect ratio of 1/d=45. Two types of tests were carried out to obtain the bond characteristics of the strands: pullout tests and beam under flexure tests. The parameters studied were the volume fraction (0%, 0,51% and 0,76%) of the fibers, and the degree of prestress of the strand (zero and 0,8fptk). The concrete compressive strength was 50 MPa at transfer (3 days of age) and 68 MPa at 28 days of age (test date), approximately. The results were analyzed and compared to the provisions of the following Codes: NBR 6118 (2001) (Brazilian code under public consult), ACI-318 (2002) and FIB-Bulletin 1 (1999). The comparison indicated that the codes give a safe design. The main conclusion of this work was that the use of 0,5% of steel fibers does not influence the bond strength of the strand. The use of 0,76% of steel fibers increases the bond stress in 28% when compared with plain concrete, for the pullout tests. For the beam\'s tests there was no bond improvement due to the steel fibers, in both case (0,5% and (0,76%), neither for the transfer length nor for the development length.

Condition assessment and safety verification of existing bridges and decisions as to whether bridge posting is required are addressed through analysis, load testing, or a combination of methods. Bridge rating through structural analysis is by far the most common procedure for rating existing bridges. The American Association of State Highway and Transportation Officials (AASHTO) Manual for Bridge Evaluation (MBE), First Edition permits bridge capacity ratings to be determined through allowable stress rating (ASR), load factor rating (LFR) or load and resistance factor rating (LRFR); the latter method is keyed to the AASHTO LRFD Bridge Design Specifications, which is reliability-based and has been required for the design of new bridges built with federal findings since October, 2007. A survey of current bridge rating practices in the United States has revealed that these three methods may lead to different ratings and posting limits for the same bridge, a situation that carries serious implications with regard to the safety of the public and the economic well-being of communities that may be affected by bridge postings or closures. To address this issue, a research program has been conducted with the overall objective of providing recommendations for improving the process by which the condition of existing bridge structures is assessed. This research required a coordinated program of load testing and finite element analysis of selected bridges in the State of Georgia to gain perspectives on the behavior of older bridges under various load conditions. Structural system reliability assessments of these bridges were conducted and bridge fragilities were developed for purposes of comparison with component reliability benchmarks for new bridges. A reliability-based bridge rating framework was developed, along with a series of recommended improvements to the current bridge rating methods, which facilitate the incorporation of various in situ conditions of existing bridges into the bridge rating process at both component and system levels. This framework permits bridge ratings to be conducted at three levels of increasing complexity to achieve the performance objectives, expressed in the terms of reliability, that are embedded in the LRFR option of the AASHTO Manual of Bridge Evaluation. This research was sponsored by the Georgia Department of Transportation, and has led to a set of Recommended Guidelines for Condition Assessment and Evaluation of Existing Bridges in Georgia.

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

Application of refined ultimate state theories and use of high strength materials have resulted in longer spans and smaller depths of reinforced and prestressed concrete structures. Consequently, the condition of the limiting deflection rather than the strength requirement often is the governing design criterion. Long-term deflections might be up to 3 to 4 times larger than the short-term deflections. Such increments are caused by complex physical effects such as concrete creep, shrinkage and cracking, bond defects, etc. Long-term concrete creep and shrinkage deformations govern prestress losses. Structural analysis can be carried out either by traditional design code methods or numerical techniques. Although design code methods ensure safe design, they have significant limitations. Different techniques are used for strength, deflection, crack width and prestress loss analyses. Besides, most of the simplified approaches do not assess such factors as concrete shrinkage, cracking or tension stiffening. Based on a large number of empirical expressions and factors, they lack physical interpretation and do not reveal the actual stress-strain state of cracked structures. On the other hand, numerical techniques are universal and can take into account each physical effect. However, inadequacies made in the prediction of each effect might lead to significant inaccuracies when integral magnitudes such as deflection are to be assessed. Consequently, the predictions by the numerical... [to full text]

This thesis investigates the performance of GFRP pretensioned concrete slabs and compares their flexural behaviour with GFRP reinforced and steel prestressed concrete slabs. A total of 12 slabs were cast in this program. The slab mid-span deflections are theoretically predicted and the results indicate that the short-term response of GFRP prestressed concrete slabs can be predicted well by the existing methods. Long-term deflection behaviour has been estimated using the Age Adjusted Effective Modulus Method by incorporating three creep and shrinkage models. A large influence of creep and shrinkage models on the theoretical determination is observed and the use of long term multipliers is not suitable for GFRP prestressed concrete members. The slabs were instrumented for long-term monitoring using strain gauges and fibre-optic sensors. It was concluded that the electrical strain gauges can be successfully used for long-term strain monitoring.

Com o surgimento da tecnologia da pré-fabricação, a construção civil tem adquirido elevada agilidade, reduzindo os prazos de construção e maior qualidade no controle de execução. Dentre as diversas peças pré-fabricadas, a telha em concreto protendido autoportante tem por característica cobrir vãos de até 25 m, sem a existência de estrutura de apoio intermediária. Sendo um produto esbelto, exige um aprimoramento constante para aumentar a durabilidade da estrutura quanto à corrosão da armadura e manter sua adequação ao uso. O objetivo desse trabalho é reduzir a permeabilidade das telhas pré-fabricadas, além de analisar a influência desse parâmetro na durabilidade do concreto frente às classes de agressividade da norma NBR 9062/2006. A norma estabelece um fator a/c máximo de 0,45 e resistência característica à compressão mínima de 40 MPa, enquadrando-se como classe de agressividade ambiental II - Urbana. Para tal, foram escolhidas algumas adições minerais existentes na região da grande Curitiba (metacaulim e filler), além de um aditivo impermeabilizante interno, comparando com o traço de referência preexistente em linha de produção. As dosagens foram definidas com base no empacotamento de partículas e caracterizadas quanto à resistência mecânica à compressão, absorção de água por imersão e por capilaridade e, penetração de água sob pressão, além dos ensaios de porosimetria por intrusão de mercúrio (PIM), carbonatação e penetração de íons cloreto. Em termos de resistência mecânica à compressão, a dosagem referência apresentou os melhores resultados (em função da menor relação água/cimento e maior consumo de cimento), seguido pelo concreto com aditivo impermeabilizante e com metacaulim. Para a absorção de água, todas as dosagens apresentaram-se como concretos duráveis, com destaque para o metacaulim e filler+aditivo impermeabilizante. Quanto à absorção capilar, todas as dosagens apresentaram baixa permeabilidade. Para a penetração de água sob pressão todas se apresentam como impermeáveis em condições agressivas, com destaque para o uso do metacaulim e do aditivo impermeabilizante. O ensaio de PIM mostra que a dosagem com filler possui uma concentração maior de poros e que a dosagem com metacaulim apresenta o menor diâmetro máximo de poros, com uma tendência ao refinamento em diâmetros menores. Quando analisado o resultado de carbonatação, o metacaulim apresentou o melhor resultado, possibilitando um menor cobrimento da armadura para uma vida útil de 50 anos. Quanto à penetração de cloretos, a dosagem com metacaulim, apresentou uma redução maior em relação às demais dosagens pela sua atividade pozolânica, contribuindo para a durabilidade do concreto. Em linhas gerais, é possível melhorar a impermeabilidade do concreto com o acréscimo de 8% do metacaulim sobre o peso do cimento, ainda com uma redução de 5,2% de cimento, com bons resultados também para o uso de 1% de aditivo impermeabilizante. Quanto à durabilidade, a otimização da curva granulométrica dos agregados e o uso do metacaulim possibilitam a utilização de telhas pré-fabricadas em regiões de classe de agressividade III - Industrial ou Marinha, observando o cobrimento mínimo da armadura. / With the emerging precast concrete technology, the civil construction has acquired high agility, reducing construction time and greater quality control in execution. Among several precast pieces, tile in prestressed concrete is characterized by selfsupporting spans of up to 25 m, without the existence of an intermediate support structure. Being a slim product, requires an improvement in increasing the durability of the structure because of the steel corrosion and maintain their fitness for use. The objective of this research is to reduce the permeability of the precast tiles, and analyzing their influence in the durability of the concrete face of the aggressiveness classes constants in the NBR 9062/2006, that establish the a/c ratio up to 0,45 and minimum compressive strength characteristic of 40 MPa, positioning themselves as a class of environmental aggressiveness II - Urban. For this, were selected a few mineral admixture from Curitiba/Paraná and a waterproof internal admixture, comparing with the concrete mix pre-existing in production line. The concrete dosages were defined by packing particles and were analysed for mechanical compressive strength, water absorption by immersion and by capillarity and water penetration under pressure, in addition to tests of mercury intrusion porosimetry (MIP), carbonation and chloride ion penetration. About the mechanical compressive strength, the dosage reference showed the best results (due to lower water / cement ratio and higher cement consumption), followed by concrete with waterproofing admixture and metakaolin. For water absorption, all measurements fall as durable concrete, especially the metakaolin additive and filler + waterproofing. For the water absorption, all dosages presented low permeability. For the water penetration under pressure all fall as impervious to several conditions, especially with metakaolin and waterproofing admixture. The MIP test shows that the dosage with filler has a higher concentration of pores and the dosage with metakaolin has the smallest maximum diameter of pores, with a tendency towards refinement in smaller diameters. When analyzing the carbonation, the metakaolin showed the best results, allowing a smaller reinforcement cover for a lifetime of 50 years. As the penetration of chlorides ions, the metakaolin, showed a greater reduction comparing with other dosages for its pozzolanic activity, contributing to the concrete durability. In general, it is possible to improve the concrete impermeability with the addition of 8% of metakaolin by weight of cement, with 5,2% of cement reduction, showing good results also using 1% of waterproofing admixture. As for durability, the optimizing of aggregates granulometric curve and the use of metakaolin enables the use of prefabricated tiles in regions of class of environmental aggressiveness III - Industrial or Marine, observing the minimum concrete cover of reinforcement.

[pt] Este trabalho apresenta um estudo experimental sobre a redistribuição de momentos em vigas contínuas de concreto construídas em aduelas pré-moldadas, com juntas secas, e protendidas com cabos sintéticos externos. Para tanto foram ensaiadas quatro vigas contínuas, com dois vãos iguais, sendo uma monolítica e as demais em aduelas pré-moldadas. Todas as vigas têm a mesma seção transversal tipo I, com dois vãos, altura da seção de 30 cm, largura do flange e espessura da alma igual a 30 cm e 10 cm, respectivamente. A viga monolítica tem relação 1/dp (vão/altura) igual a 18,75 e nas vigas em aduelas os valores desta relação foram entre 12,5, 18,75 e 25. As vigas são protendidas com dois cabos sintéticos externos com traçado poligonal. Os cabos utilizados são feitos com fibras sintéticas de alta resistências (2700 MPa) e alto modulo de elasticidade (126000 MPa) conhecidas comercialmente como Kevlar. O objetivo deste estudo é examinar a redistribuição de momentos em vigas contínuas com sistemas construtivos diferentes e com diferentes relações 1/dp frente à utilização de cabos sintéticos. Os resultados mostram que a redistribuição de momentos em vigas em aduelas pode ser obtida a partir de uma viga monolítica semelhante e que o comportamento da redistribuição de momentos nas vigas em aduelas é pouco influenciada pela relação l/dp. / [en] An experimental investigation on the behavior of continuous segmental concrete beams, prestressed with external aramid tendons, was carried out. Four beams were tested; one was monolithic and the others were constructed in precast dry- jointed segments. All the beams had the same overall dimensions, with two spans and an I section 30 cm high, flange width of 30 cm and web thickness of 10 cm. The 1/dp span/section height) ratio was 18,75 for the monolithic beam and 12.5, 18.75 and 25 for the segmental beams. The beams were post-tensioned with two external aramid tendons, which are made of high strength (2700 MPa) high modulus (126000 MPa)Kevlar 49 yarns. The main objective was to study the moment redistribution in the post-cracking stage. Test results have shown that the moment redistribution in segmental beams can be obtained from a similar monolithic beam and that the moment redistribution is only slightly affected by the 1/dp.

[pt] No presente trabalho foi estudado o comportamento mecânico do concreto reforçado com fibras de aço na escala do material e estrutural. A caracterização da matriz foi realizada por meio de ensaios de compressão para diferentes idades. Foram realizados ensaios de flexão em três pontos, e ensaios de tração direta em corpos de prova no formato de dog bone, tanto para a matriz quanto para concretos reforçados com fibras de aço. As fibras eram providas de ganchos nas extremidades, com comprimentos de 30, 35 e 60 mm e diâmetros de 0,62, 0,55 e 0,75 mm, respectivamente. As frações volumétricas adotadas foram 0,25, 0,5 e 1,0 por cento. A adição de fibras promoveu aumento na tenacidade e na resistência residual do concreto tanto nos ensaios de flexão quanto tração direta. Ensaios de tração direta em tirantes de concreto armado foram conduzidos para a matriz e para concretos reforçados com 1,0 por cento das fibras de 35 e 60 mm de comprimento. Foi observado que a adição de fibras controlou a abertura de fissuras, aumentou a rigidez pós fissuração e a aderência barra-concreto. Na escala estrutural, ensaios de momento negativo no meio do vão foram conduzidos em dormentes de concreto protendido sem reforço e com 0,5 por cento de fibras de comprimento 35 e 60 mm. O momento de primeira fissura, momento último e a tenacidade foram incrementadas com a adição de fibras no dormente. Os resultados experimentais foram verificados por cálculo teórico. O incremento no momento último pela adição de fibras seguiu o mesmo padrão apresentado experimentalmente. / [en] This work presents an evaluation of the mechanical behavior of steel fiber reinforced concrete on a material and structural scale. The characterization of the matrix was performed by compression tests for different ages. Three-point bending tests and direct tensile tests on dog bone specimens were performed for the matrix and for concrete reinforced with steel fibers. The fibers had hooked-end geometry, were 30, 35 and 60 mm long and had diameters of 0.62, 0.55 and 0.75 mm, respectively. The volume fractions were 0.25, 0.5 and 1.0 per cent. The addition of fibers promoted an increase in toughness and residual strength of the concrete in both the flexural and direct tensile tests. Tension stiffening tests were conducted on the matrix and on concretes reinforced with 1.0 per cent of the 35 and 60 mm long fibers. It was observed that the addition of fibers controlled the crack opening, increased post-cracking stiffness and bar-concrete adhesion. In the structural scale, negative bending moment tests at mid span were conducted on reinforced concrete sleepers with 0.5 per cent of the 35 and 60 mm long fibers. The first crack strength, ultimate strength and toughness were increased with the addition of fibers on the sleeper. The experimental results were verified by theoretical calculations. The increment ratio of the ultimate moment by the fiber addition was the same for the theoretical and experimental analysis.