A técnica caracterizada pela colagem de polímeros reforçados com fibras de carbono (PRFC) em elementos estruturais de concreto vem sendo aplicada com sucesso no reforço de estruturas em todo o mundo. Resistência à corrosão, elevada resistência à tração, baixo peso, facilidade e rapidez de aplicação, são algumas das características interessantes que têm contribuído para a sua disseminação. Nesta pesquisa propõe-se uma inovação construtiva fundamentada no desenvolvimento de um compósito de alto desempenho à base de cimento Portland e fibras de aço (macro + microfibras), destinado a constituir o que está sendo preliminarmente chamado de substrato de transição. A finalidade desse substrato é a de controlar melhor a fissuração do concreto da viga e retardar ou até evitar o desprendimento prematuro do reforço polimérico. Devido à carência de pesquisas semelhantes a aqui proposta, foi realizado um estudo preliminar em vigotas moldadas com fibras de aço e reforçadas externamente com manta de PRFC, onde se verificou que a concepção do substrato de transição é válida. Partiu-se então para a realização de ensaios visando à obtenção de um compósito cimentício com características apropriadas para constituir o substrato de transição. Os resultados e as análises efetuadas mostram que foi possível desenvolver um material de elevado desempenho, traduzido por um comportamento de pseudo-encruamento, com elevados ganhos de resistência e tenacidade ao fraturamento. A aplicação do reforço com manta sobre a superfície do substrato de transição, formado a partir da reconstituição do banzo tracionado da viga com o compósito cimentício, mostrou melhorar significativamente os níveis de desempenho da peça reforçada. Do estudo realizado foi possível comprovar a eficiência da técnica de reforço proposta, além de reunir uma série de informações que podem ser exploradas para se tornarem úteis como critérios de projeto de estruturas recuperadas e reforçadas. / The technique characterized by bond of the carbon fibers reinforced polymer (CFRP) in structural elements of concrete comes being applied successfully in the strengthening of structures in the whole world. Resistance to the corrosion, high tensile strength, low weight, easiness and rapidity of application, is some of interesting characteristics that have contributed for its dissemination. The objective of this research is to develop an innovate strengthening method for RC beams, based on a high performance cement-based composite of steel fibers (macro + microfibers) to be applied in a transition layer. The purpose of this transition layer is to better control the cracking of concrete and to be late or until avoid the premature detachment of strengthening. Due to lack of similar research here the proposal, was carried through a preliminary study in short beams molded with steel fibers and strengthened with CFRP sheet, where if it verified that the conception of the transition layer is valid. Tests were developed to get a cement-based composite with characteristics to constitute the layer transition. The results shown that were possible to develop a material of high performance with a pseudo strain-hardening behavior, high strength and fracture toughness. The application of the strengthened about the layer transition surface showed significantly to improve the levels of performance of the strengthening beam. Of the carried through study it was possible to prove the efficiency of the new strengthened technique and describe various information that can be explored to become useful as criteria of project of repaired and strengthened structures.

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 o desenvolvimento de uma técnica de incremento da resistência e da rigidez à flexão de ligações de elementos de concreto pré-moldado, com aplicação de laminados de polímero reforçado com fibra de carbono (PRFC). O procedimento adotado consiste na colagem dos laminados de PRFC em entalhes no concreto de cobrimento, de acordo com a técnica conhecida como \"near-surface mounted\" (NSM), de modo a incorporar à ligação novos elementos resistentes à tração. Para solidarizar a ligação e possibilitar a transferência de esforços de compressão entre os elementos de concreto existentes, preenchem-se os espaços vazios (grauteamento) com argamassa fluida à base de cimento Portland. Foram desenvolvidos modelos em escala reduzida, com o intuito de representar os mecanismos resistentes de uma ligação viga-pilar composta por encaixe de dente Gerber e consolo, com uso de chumbador, almofada de apoio e graute. Esse tipo de ligação é muito utilizado na construção de galpões e tem, na sua concepção original, comportamento essencialmente de articulação. Em uma etapa preliminar, realizaram-se ensaios para a caracterização da aderência segundo a configuração de reforço proposta. Os resultados dessa análise subsidiaram a fixação do comprimento de laminado a ancorar e a escolha do tipo de resina a empregar para colagem do reforço. Os modelos representativos da técnica de reforço proposta foram preparados, cada um deles, pela montagem de um elemento de pilar-consolo com elementos de viga nos respectivos chumbadores e almofadas. Foram também preparados modelos de referência para o estudo da influência da almofada de apoio e do grauteamento no comportamento resistente e da deformabilidade da ligação. Nesses modelos, as juntas eram perfeitamente conjugadas, isto é, os trechos de viga foram concretados com um elemento pré-moldado de pilar-consolo posicionado dentro da fôrma, sem disposição de almofadas. Todos os modelos de ligação foram reforçados e submetidos a ensaios estáticos. Esses ensaios consistiram na aplicação de carregamento cíclico alternado de curta duração, solicitando-se os modelos a momento fletor positivo ou negativo. Este trabalho também apresenta procedimento executivo de ensaios dinâmicos para avaliação da rigidez dos modelos de ligação em três condições: modelo íntegro reforçado, modelo reforçado fissurado (após aplicação de carregamento de aproximadamente 30% do carregamento de ruptura da ligação, em ensaio estático) e modelo reforçado rompido. Com o reforço, a ligação apresentou comportamento semi-rígido e adquiriu resistência à flexão compatível à de estrutura monolítica armada com barras de PRF. / This work presents the development of a technique for flexural strengthening and stiffness increasing of precast beam-to-column connections by the embedding of FRP strips into grooves made on the concrete cover. According to this technique, the tension in the connection is transferred by the Near-Surface Mounted (NSM) FRP strips. To allow the transference of compression efforts among the concrete elements, the empty spaces are filled out with grout. Small-scale specimens were developed to represent the resistant mechanisms of pined beam-to-column connection composed by elastomeric cushion and dowels. Preliminary experimental tests on bond behavior of NSM strips were carried out. The results analysis conducted the decision about the adhesive type and bond length to be employed in the beam-to-column connection specimens. Each specimen was made of the assembly of a column section connected to beam sections through their respective dowels and cushions. The connection specimens were reinforced by embedding CFRP strips in the lateral concrete cover and filling out the spaces between beams and column. In addition, control specimens were prepared to study the influence of the cushion and grout in the connection performance. In those models, the joints were conjugated perfectly, which means that the beam sections were laid inside the wooden forms and cast together with a precast column section with no cushions between them. Experimental static and dynamic tests were done. The tests results show that strengthened connection exhibits semi-rigid behavior and acquires flexural strength compatible to monolithic structure reinforced with FRP bars.

The introduction of fibre-reinforced polymers (FRPs) to the field of civil engineering has led to numerous research efforts focusing on a wide range of applications where properties such as high strength, light weight or corrosion resistance are desirable. In particular, FRP materials have been especially attractive for use as internal reinforcement in reinforced concrete (RC) structures exposed to aggressive environments due to the rapidly deteriorating infrastructure resulting from corrosion of conventional steel reinforcement. While FRPs have been successfully implemented in a variety of structural applications, little research has been conducted on the use of FRP reinforcement for short span slab bridges. Furthermore, the behaviour of FRP-RC flexural members cast with self-consolidating concrete (SCC) is largely absent from the literature. The present study investigates the behaviour of an all-FRP reinforcement system for slab bridges which combines lower cost glass FRP (GFRP) reinforcing bars with high performance carbon FRP (CFRP) prestressed tendons in SCC to produce a structure which is both cost-efficient and characterized by excellent structural performance at the serviceability, ultimate and fatigue limit states. An extensive experimental program comprised of 57 large or full-scale slab strips was conducted to investigate the effects of reinforcement type, reinforcement ratio, prestressing level and shear reinforcement type on the flexural performance of slab bridges under both monotonic and fatigue loading. The proposed reinforcement system was found to display excellent serviceability characteristics and high load capacities as well as significant deformability to allow for sufficient warning prior to failure. Lastly, the use of post-tensioned CFRP tendons limited the stresses in the GFRP reinforcing bars leading to significantly longer fatigue lives and higher fatigue strengths compared to non-prestressed slabs. Analytical models were used to predict the behaviour of the slab bridge strips at service and at ultimate. Where these models failed to accurately represent the experimental findings, simple modifications were proposed. The results from ancillary tests were also used to modify existing analytical models to predict the effects of fatigue loading on the deflection, crack width, shear resistance and flexural capacity of each of the tested slabs.

Safety and reliability are prime concerns in aircraft performance due to the involved costs and risk to lives. Despite the best efforts in design methodology, quality evaluation in production and structural integrity assessment in-service, attainment of one hundred percent safety through development and use of a suitable in-flight health monitoring system is still a farfetched goal. And, evolution of such a system requires, first, identification of an appropriate Technique and next its adoption to meet the challenges posed by newer materials (advanced composites), complex structures and the flight environment. In fact, a quick survey of the available Non-Destructive Evaluation (NDE) techniques suggests Acoustic Emission (AE) as the only available method. High merit in itself could be a weakness - Noise is the worst enemy of AE. So, while difficulties are posed due to the insufficient understanding of the basic behavior of composites, growth and interaction of defects and damage under a specified load condition, high in-flight noise further complicates the issue making the developmental task apparently formidable and challenging. Development of an in-flight monitoring system based on AE to function as an early warning system needs addressing three aspects, viz., the first, discrimination of AE signals from noise data, the second, extraction of required information from AE signals for identification of sources (source characterization) and quantification of its growth, and the third, automation of the entire process. And, a quick assessment of the aspects involved suggests that Artificial Neural Networks (ANN) are ideally suited for solving such a complex problem. A review of the available open literature while indicates a number of investigations carried out using noise elimination and source characterization methods such as frequency filtering and statistical pattern recognition but shows only sporadic attempts using ANN. This may probably be due to the complex nature of the problem involving investigation of a large number of influencing parameters, amount of effort and time to be invested, and facilities required and multi-disciplinary nature of the problem. Hence as stated in the foregoing, the need for such a study cannot be over emphasized. Thus, this thesis is an attempt addressing the issue of analysis and automation of complex sets of AE data such as AE signals mixed with in-flight noise thus forming the first step towards in-flight monitoring using AE. An ANN can in fact replace the traditional algorithmic approaches used in the past. ANN in general are model free estimators and derive their computational efficiency due to large connectivity, massive parallelism, non-linear analog response and learning capabilities. They are better suited than the conventional methods (statistical pattern recognition methods) due to their characteristics such as classification, pattern matching, learning, generalization, fault tolerance and distributed memory and their ability to process unstructured data sets which may be carrying incomplete information at times and hence chosen as the tool. Further, in the current context, the set of investigations undertaken were in the absence of sufficient a priori information and hence clustering of signals generated by AE sources through self-organizing maps is more appropriate. Thus, in the investigations carried out under the scope of this thesis, at first a hybrid network named "NAEDA" (Neural network for Acoustic Emission Data Analysis) using Kohonen self-organizing feature map (KSOM) and multi-layer perceptron (MLP) that learns on back propagation learning rule was specifically developed with innovative data processing techniques built into the network. However, for accurate pattern recognition, multi-layer back propagation NN needed to be trained with source and noise clusters as input data. Thus, in addition to optimizing the network architecture and training parameters, preprocessing of input data to the network and multi-class clustering and classification proved to be the corner stones in obtaining excellent identification accuracy. Next, in-flight noise environment of an aircraft was generated off line through carefully designed simulation experiments carried out in the laboratory (Ex: EMI, friction, fretting and other mechanical and hydraulic phenomena) based on the in-flight noise survey carried out by earlier investigators. From these experiments data was acquired and classified into their respective classes through MLP. Further, these noises were mixed together and clustered through KSOM and then classified into their respective clusters through MLP resulting in an accuracy of 95%- 100% Subsequently, to evaluate the utility of NAEDA for source classification and characterization, carbon fiber reinforced plastic (CFRP) specimens were subjected to spectrum loading simulating typical in-flight load and AE signals were acquired continuously up to a maximum of three designed lives and in some cases up to failure. Further, AE signals with similar characteristics were grouped into individual clusters through self-organizing map and labeled as belonging to appropriate failure modes, there by generating the class configuration. Then MLP was trained with this class information, which resulted in automatic identification and classification of failure modes with an accuracy of 95% - 100%. In addition, extraneous noise generated during the experiments was acquired and classified so as to evaluate the presence or absence of such data in the AE data acquired from the CFRP specimens. In the next stage, noise and signals were mixed together at random and were reclassified into their respective classes through supervised training of multi-layer back propagation NN. Initially only noise was discriminated from the AE signals from CFRP failure modes and subsequently both noise discrimination and failure mode identification and classification was carried out resulting in an accuracy of 95% - 100% in most of the cases. Further, extraneous signals mentioned above were classified which indicated the presence of such signals in the AE signals obtained from the CFRP specimen. Thus, having established the basis for noise identification and AE source classification and characterization, two specific examples were considered to evaluate the utility and efficiency of NAEDA. In the first, with the postulation that different basic failure modes in composites have unique AE signatures, the difference in damage generation and progression can be clearly characterized under different loading conditions. To examine this, static compression tests were conducted on a different set of CFRP specimens till failure with continuous AE monitoring and the resulting AE signals were classified through already trained NAEDA. The results obtained shows that the total number of signals obtained were very less when compared to fatigue tests and the specimens failed with hardly any damage growth. Further, NAEDA was able to discriminate the"noise and failure modes in CFRP specimen with the same degree of accuracy with which it has classified such signals obtained from fatigue tests. In the second example, with the same postulate of unique AE signatures for different failure modes, the differences in the complexion of the damage growth and progression should become clearly evident when one considers specimens with different lay up sequences. To examine this, the data was reclassified on the basis of differences in lay up sequences from specimens subjected to fatigue. The results obtained clearly confirmed the postulation. As can be seen from the summary of the work presented in the foregoing paragraphs, the investigations undertaken within the scope of this thesis involve elaborate experimentation, development of tools, acquisition of extensive data and analysis. Never the less, the results obtained were commensurate with the efforts and have been fruitful. Of the useful results that have been obtained, to state in specific, the first is, discrimination of simulated noise sources achieved with significant success but for some overlapping which is not of major concern as far as noises are concerned. Therefore they are grouped into required number of clusters so as to achieve better classification through supervised NN. This proved to be an innovative measure in supervised classification through back propagation NN. The second is the damage characterization in CFRP specimens, which involved imaginative data processing techniques that proved their worth in terms of optimization of various training parameters and resulted in accurate identification through clustering. Labeling of clusters is made possible by marking each signal starting from clustering to final classification through supervised neural network and is achieved through phenomenological correlation combined with ultrasonic imaging. Most rewarding of all is the identification of failure modes (AE signals) mixed in noise into their respective classes. This is a direct consequence of innovative data processing, multi-class clustering and flexibility of grouping various noise signals into suitable number of clusters. Thus, the results obtained and presented in this thesis on NN approach to AE signal analysis clearly establishes the fact that methods and procedures developed can automate detection and identification of failure modes in CFRP composites under hostile environment, which could lead to the development of an in-flight monitoring system.

Detta examensarbete har utförts på uppdrag av Koenigsegg Automotive AB, som utvecklar, tillverkar och säljer högpresterande sportbilar. Företaget erbjuder fälgar tillverkade helt i kolfiberkomposit, som ger betydande viktbesparingar i jämförelse med traditionella metallfälgar. Efter tillverkningen kräver fälgarna viss bearbetning vid anläggningsytan mellan fälg och däck. Syftet med examensarbetet har varit att undersöka möjligheten att utföra bearbetningen av fälgarna in-house i Ängelholm, och målet har varit att konstruera en maskin för detta ändamål. Projektet inleddes med en litteratursökning, där svårigheter och möjligheter gällande bearbetning av kolfiberkompositer undersöktes. Till följd av de undersökningar som gjordes, valdes bearbetningsmetoden svarvfräsning och ett antal konstuktionskoncept genererades. Genom ett antal utvärderingar utvecklades ett speciellt koncept vidare till ett komplett produktförslag. Produktförslaget är komplett med analyser, beräkningar samt tillverkningsunderlag, som ger uppdragsgivaren bättre insikt i sina möjligheter. Även underlag som tillåter en framtida CE-märkning har tagits fram. Projektet har följt Fredy Olssons konstruktionsmetod. / The following thesis has been performed in cooperation with Koenigsegg Automotive AB, which develops, manufactures and sells high-performance sportscars. Koenigsegg offers rims made completely from carbon fiber composite, which yields substantial benefits in stiffness and weight compared to their traditional metal counterparts. After the manufacturing of the rims, some trimming is necessary in the contact surface between rim and tire. The purpose of this thesis has been to examine the possibility of performing the necessary trimming in-house in Ängelholm, by designing a special tool. The project began with a literature study, where possibilities and difficulties of machining carbon fiber composites were examined. As a result of the study, the manufacturing process turn-milling was chosen, and a number of concepts were generated. Through a series of evaluations, one concept was further developed to a final product. The suggested product is complete with calculations, analyses and drawings, which gives Koenigsegg a better insight of future possibilities. A solid foundation for future CE-marking has also been produced. The project has followed Fredy Olssons methods of Engineering Design.

The introduction of fibre-reinforced polymers (FRPs) to the field of civil engineering has led to numerous research efforts focusing on a wide range of applications where properties such as high strength, light weight or corrosion resistance are desirable. In particular, FRP materials have been especially attractive for use as internal reinforcement in reinforced concrete (RC) structures exposed to aggressive environments due to the rapidly deteriorating infrastructure resulting from corrosion of conventional steel reinforcement. While FRPs have been successfully implemented in a variety of structural applications, little research has been conducted on the use of FRP reinforcement for short span slab bridges. Furthermore, the behaviour of FRP-RC flexural members cast with self-consolidating concrete (SCC) is largely absent from the literature. The present study investigates the behaviour of an all-FRP reinforcement system for slab bridges which combines lower cost glass FRP (GFRP) reinforcing bars with high performance carbon FRP (CFRP) prestressed tendons in SCC to produce a structure which is both cost-efficient and characterized by excellent structural performance at the serviceability, ultimate and fatigue limit states. An extensive experimental program comprised of 57 large or full-scale slab strips was conducted to investigate the effects of reinforcement type, reinforcement ratio, prestressing level and shear reinforcement type on the flexural performance of slab bridges under both monotonic and fatigue loading. The proposed reinforcement system was found to display excellent serviceability characteristics and high load capacities as well as significant deformability to allow for sufficient warning prior to failure. Lastly, the use of post-tensioned CFRP tendons limited the stresses in the GFRP reinforcing bars leading to significantly longer fatigue lives and higher fatigue strengths compared to non-prestressed slabs. Analytical models were used to predict the behaviour of the slab bridge strips at service and at ultimate. Where these models failed to accurately represent the experimental findings, simple modifications were proposed. The results from ancillary tests were also used to modify existing analytical models to predict the effects of fatigue loading on the deflection, crack width, shear resistance and flexural capacity of each of the tested slabs.

Prestressed hollow core slabs are essential components in structures such as bridges, parking garages, marine structures, and commercial and industrial buildings. Material degradation and altered functional requirements may seriously threaten the structural integrity of these reinforced concrete structures. Using FRP composites, the NSM strengthening technique presents a viable solution to these challenges. However, further investigation is required to establish comprehensive empirical design guidelines. The intent of this research project is to investigate the NSM technique in conjunction with common design concepts such as prestressed concrete, precast hollow core slabs, the complex behaviour of disturbed regions, and fiber-reinforced composite materials. An experimental program was developed, which included eleven full-scale slab specimens, subject to a four-point load configuration. The main parameters included the prestressing reinforcement ratio, CFRP strengthening ratio, and in-service opening location. Experimental results showed that prestressed concrete strengthened in flexure with NSM-CFRP is a viable technique for lower reinforcement ratios.

O objetivo deste trabalho é apresentar um modelo para análise probabilística de vigas de concreto armado recuperadas à flexão, através da utilização conjunta do método de simulação de Monte Carlo e do método dos Elementos Finitos. Para uma análise da confiabilidade, foram projetadas vigas de concreto armado seguindo as recomendações da NRR 6118:2003. Após, foi considerado que as armaduras tracionadas de flexão sofreram reduções de 10%, 20% e 30% na sua área da seção transversal, sendo, então, feita uma análise da segurança estrutural remanescente. Para o projeto de recuperação das vigas danificadas, estão apresentados os procedimentos do Bulletin 14 da fédération internationale du béton (fib) para o dimensionamento de sistemas de reforço com material compósito colado externamente às estruturas. Assim, a confiabilidade destas vigas recuperadas pôde ser estimada e comparada à confiabilidade das vigas originais. Dentro do processo de simulação, a resposta em termos da carga de ruptura das vigas de concreto armado recuperadas foi obtida através de uma análise numérica não-linear utilizando um modelo de elementos finitos. Devido à importância do deslizamento entre o substrato de concreto e o sistema de reforço estrutural, foram implementados dentro do modelo de elementos finitos, elementos unidimensionais de interface, quadráticos com seis pontos nodais para a captura deste comportamento. As análises probabilísticas através do método de simulação de Monte Carlo usando um modelo de elementos finitos mostraram que se atinge bom nível de segurança no projeto de vigas de concreto armado seguindo as recomendações da NBR 6118:2003. Entretanto, danos nas armaduras tracionadas de flexão podem fazer com que a confiabilidade caía para níveis inaceitáveis. Como solução, o projeto de recuperação estrutural de acordo com o Bulletin 14 da fib fez com que a confiabilidade das vigas recuperadas fosse no mínimo igual à confiabilidade das vigas originais. Assim, a probabilidade de falha das vigas recuperadas foi menor quando comparado à probabilidade de falha das vigas originais. / The objective of this work is to present a model for probabilistic analysis of RC beams rehabilitated for flexure, through the simultaneous utilization of the Monte Carlo method and the finite element method. Initially, three RC beams were designed following the NBR 6118:2003 recommendations. In the next step, it was considered that a reduction of the steel reinforcement area of 10%, 20% and 30% had occurred. Then the procedures for strengthening systems design with externally bonded carbon fiber reinforced polymers (fib, Bulletin 14) were employed for the rehabilitation of the damaged RC beams. Finally, the reliability of the RC beams rehabilitated for flexure could be evaluated and compared to that of the damaged and undamaged RC beams. In the Monte Carlo method, the RC beams failure load was obtained numerically through a nonlinear finite element model. Due to the importance of the slip between the concrete substrate and the external reinforcement, it was introduced in the finite element model a special one-dimensional interface element, with six nodal points and quadratic shape functions. The probabilistic analysis through the Monte Carlo method using a finite element model showed the high reliability attained in the RC beams design following the NBR 6118:2003 recommendations. However, the damage in the internal steel reinforcement can lead to an unacceptable reliability level. As a solution, the design of structural recovery according to the Bulletin 14 produced a reliability level for the RC beams rehabilitated for flexure at least equal to the reliability level of the undamaged RC beams. Consequently, the failure probability of the RC beams rehabilitated for flexure was lower then the failure probability of the undamaged RC beams.

O objetivo deste trabalho é apresentar um modelo para análise probabilística de vigas de concreto armado recuperadas à flexão, através da utilização conjunta do método de simulação de Monte Carlo e do método dos Elementos Finitos. Para uma análise da confiabilidade, foram projetadas vigas de concreto armado seguindo as recomendações da NRR 6118:2003. Após, foi considerado que as armaduras tracionadas de flexão sofreram reduções de 10%, 20% e 30% na sua área da seção transversal, sendo, então, feita uma análise da segurança estrutural remanescente. Para o projeto de recuperação das vigas danificadas, estão apresentados os procedimentos do Bulletin 14 da fédération internationale du béton (fib) para o dimensionamento de sistemas de reforço com material compósito colado externamente às estruturas. Assim, a confiabilidade destas vigas recuperadas pôde ser estimada e comparada à confiabilidade das vigas originais. Dentro do processo de simulação, a resposta em termos da carga de ruptura das vigas de concreto armado recuperadas foi obtida através de uma análise numérica não-linear utilizando um modelo de elementos finitos. Devido à importância do deslizamento entre o substrato de concreto e o sistema de reforço estrutural, foram implementados dentro do modelo de elementos finitos, elementos unidimensionais de interface, quadráticos com seis pontos nodais para a captura deste comportamento. As análises probabilísticas através do método de simulação de Monte Carlo usando um modelo de elementos finitos mostraram que se atinge bom nível de segurança no projeto de vigas de concreto armado seguindo as recomendações da NBR 6118:2003. Entretanto, danos nas armaduras tracionadas de flexão podem fazer com que a confiabilidade caía para níveis inaceitáveis. Como solução, o projeto de recuperação estrutural de acordo com o Bulletin 14 da fib fez com que a confiabilidade das vigas recuperadas fosse no mínimo igual à confiabilidade das vigas originais. Assim, a probabilidade de falha das vigas recuperadas foi menor quando comparado à probabilidade de falha das vigas originais. / The objective of this work is to present a model for probabilistic analysis of RC beams rehabilitated for flexure, through the simultaneous utilization of the Monte Carlo method and the finite element method. Initially, three RC beams were designed following the NBR 6118:2003 recommendations. In the next step, it was considered that a reduction of the steel reinforcement area of 10%, 20% and 30% had occurred. Then the procedures for strengthening systems design with externally bonded carbon fiber reinforced polymers (fib, Bulletin 14) were employed for the rehabilitation of the damaged RC beams. Finally, the reliability of the RC beams rehabilitated for flexure could be evaluated and compared to that of the damaged and undamaged RC beams. In the Monte Carlo method, the RC beams failure load was obtained numerically through a nonlinear finite element model. Due to the importance of the slip between the concrete substrate and the external reinforcement, it was introduced in the finite element model a special one-dimensional interface element, with six nodal points and quadratic shape functions. The probabilistic analysis through the Monte Carlo method using a finite element model showed the high reliability attained in the RC beams design following the NBR 6118:2003 recommendations. However, the damage in the internal steel reinforcement can lead to an unacceptable reliability level. As a solution, the design of structural recovery according to the Bulletin 14 produced a reliability level for the RC beams rehabilitated for flexure at least equal to the reliability level of the undamaged RC beams. Consequently, the failure probability of the RC beams rehabilitated for flexure was lower then the failure probability of the undamaged RC beams.