Thesis (MScEng)-- Stellenbosch University, 2013. / ENGLISH ABSTRACT: Concrete is used in most of the modern day infrastructure. It is a building material for which there exist various design codes and guidelines for its use and construction. It is strong in compression, but lacks tensile strength in its fresh and hardened states and, when unreinforced, fails in a brittle manner. The structural use of synthetic fibres in concrete is investigated in this study to determine its effect on enhancing the mechanical properties of concrete. Slabs on grade are used as the application for which the concrete is tested. The material behaviour is investigated in parallel with two floor design theories. These are the Westegaard theory and the Yield-Line theory. The Westegaard theory uses elastic theory to calculate floor thicknesses while the Yield-Line theory includes plastic behaviour. Conceptual designs are performed with the two theories and material parameters are determined from flexural tests conducted on synthetic fibre reinforced concrete (SynFRC) specimens. Large scale slab tests are performed to verify design values from the two theories. Higher loads till first-crack were measured during tests with concrete slabs reinforced with polypropylene fibres than for unreinforced concrete. It is found that the use of synthetic fibres in concrete increases the post-crack ductility of the material. The Westegaard theory is conservative in its design approach by over-estimating design thicknesses. This was concluded as unreinforced slabs reached higher failure loads than predicted by this theory. The Yield-Line theory predicts design thicknesses more accurately while still accounting for the requirements set by the ultimate- and serviceability limit states. By using SynFRC in combination with the Yield-Line theory as design method, thinner floor slabs can be obtained than with the Westegaard theory. / AFRIKAANSE OPSOMMING: Beton word gebruik as boumateriaal in meeste hedendaagse infrastruktuur. Daar bestaan verskeie ontwerp kodes en riglyne vir die gebruik en oprig van beton strukture. Alhoewel beton sterk in kompressie is, het beton ‘n swak treksterkte in beide die vars- en harde fases en faal dit in ‘n bros manier indien onbewapen. Die gebruik van sintetiese vesels in beton word in hierdie projek ondersoek om die invloed daarvan op die eienskappe van die meganiesegedrag van beton te bepaal. Grond geondersteunde vloere word as toepassing gebruik. Parallel met die materiaalgedrag wat ondersoek word, word twee ontwerpsteorieë ook ondersoek. Dit is die teorie van Westegaard en die Swig-Lyn teorie. Die teorie van Westegaard gebruik elastiese teorie in ontwerpsberekeninge terwyl die Swig-Lyn teorie ‘n plastiese analise gebruik. ‘n Konseptuele vloerontwerp is gedoen deur beide die ontwerpsmetodes te gebruik. Materiaalparameters is bepaal deur buig-toetse uit te voer op sintetiesevesel-bewapende beton. Grootskaalse betonblaaie is gegiet en getoets om die akkuraatheid van die twee metodes te verifieer. Die betonblaaie wat bewapen was met polipropileen vesels het groter laste gedra tot by faling as die blaaie wat nie bewapen was nie. Die vesels verbeter die gedrag van beton in die plastiese gebied van materiaalgedrag deurdat laste ondersteun word nadat die beton alreeds gekraak het. Die Westegaard teorie kan as konserwatief beskou word deurdat dit vloerdiktes oorskat. Hierdie stelling is gegrond op eksperimentele data wat bewys dat onbewapende betonblaaie groter laste kan dra as wat voorspel word deur die Westegaard teorie. Die Swig-Lyn teorie voorspel ontwerpsdiktes meer akkuraat terwyl daar steeds aan die vereistes van swigting en diensbaarheid voldoen word. Deur gebruik te maak van sintetiese vesels en die Swig-Lyn teorie kan dunner betonblaaie ontwerp word as met die Westegaard teorie.

Use of fiber reinforced polymer (FRP) material has been a good solution for many problems in many fields. FRP is available in different types (carbon and glass) and shapes (sheets, rods, and laminates). Civil engineers have used this material to overcome the weakness of concrete members that may have been caused by substandard design or due to changes in the load distribution or to correct the weakness of concrete structures over time specially those subjected to hostile weather conditions. The attachment of FRP material to concrete surfaces to promote the function of the concrete members within the frame system is called Externally Bonded Fiber Reinforced Polymer Systems. Another common way to use the FRP is called Near Surface Mounted (NSM) whereby the material is inserted into the concrete members through grooves within the concrete cover. Concrete beam-column joints designed and constructed before 1970s were characterized by weak column-strong beam. Lack of transverse reinforcement within the joint reign, hence lack of ductility in the joints, and weak concrete could be one of the main reasons that many concrete buildings failed during earthquakes around the world. A technique was used in the present work to compensate for the lack of transverse reinforcement in the beam-column joint by using the carbon fiber reinforced polymer (CFRP) sheets as an Externally Bonded Fiber Reinforced Polymer System in order to retrofit the joint region, and to transfer the failure to the concrete beams. Six specimens in one third scale were designed, constructed, and tested. The proposed retrofitting technique proved to be very effective in improving the behavior of non-ductile beam-column joints, and to change the final mode of failure. The comparison between beam-column joints before and after retrofitting is presented in this study as exhibited by load versus deflection, load versus CFRP strain, energy dissipation, and ductility.

Abstract not available

The shear capacity of reinforced concrete pier caps in existing bridge support systems can be a factor which limits the capacity of an existing bridge. In their usual configuration, pier caps behave as deep beams and have the ability to carry load through tied arch action after the formation of diagonal cracks. Externally bonded fiber reinforced polymer (FRP) reinforcement has been shown to increase the shear capacity of reinforced concrete members which carry load through beam action. However, there is an insufficient amount of research to make it a viable strengthening system for beams which carry load through arch action, such as pier caps. Accordingly, this research was aimed at investigating the behavior of reinforced concrete pier caps through a coordinated experimental and analytical program and to recommend an external strengthening method for pier caps with perceived deficiencies in shear strength. The experimental study was performed on laboratory specimens based on an existing bridge in Georgia. A number of factors were examined, including size, percentage longitudinal reinforcement and crack control reinforcement. The results showed that increasing the longitudinal tension reinforcement increased the beam capacity by changing the shape of the tied arch. In contrast, the presence of crack control reinforcement did not change the point at which diagonal cracking occurred, but it did increase the ultimate capacity by reinforcing the concrete against splitting. The results of the experimental study were used in conjunction with a larger database to examine different analytical methods for estimating the ultimate capacity of deep beams, and a new method was developed for the design of external strengthening. Two specimens were tested with externally bonded FRP reinforcement applied longitudinally to increase the strength of the tension tie. The test results correlated well with the proposed method of analysis and showed that increasing the strength of the longitudinal tension tie is an effective way to increase the strength of a reinforced concrete deep beam.

Procurando conhecer o grau de deterioração precoce das estruturas de concreto armado dos edifícios residenciais da Região Metropolitana da Cidade do Recife, Estado de Pernambuco, este trabalho visa, utilizando um método de quantificação dos danos e o uso de ensaios, avaliar as patologias das estruturas estudadas. Estudou-se três edifícios residenciais (ER), com semelhante padrão de construção, idades construtivas aproximadas e inseridos em diferentes classes de agressividade ambiental. Foi realizada inspeção visual e ensaios em amostras dos pilares, vigas, lajes e reservatório inferior do subsolo dos três edifícios. Após análise dos três edifícios, verificou-se que o caso ER 1, localizado em classe ambiental de agressividade forte (III), a mais agredida pelo meio ambiente, e o estudo de caso ER 2, localizado a uma distância significativa da orla marinha em Classe de Agressividade Ambiental II, apresentaram grau de deterioração media (GD) de 36,98 e 31,23 respectivamente, com recomendação para inspeção periódica e intervenção a médio prazo. Já o estudo de caso ER 3, que está localizado dentro da uma classe de agressividade forte (III), em orla marinha, porém com barreiras de proteção que evitam a incidência direta da névoa salina, encontra-se com alto grau de deterioração (GD = 103,94), sugerindo uma intervenção imediata com riscos de colapso / This work aims to evaluate the pathology of residential buildings structures located at the Metropolitan Region of Recife, Brazil using the quantification of damages to measure the degree of early deterioration of reinforced concrete. Three residential buildings (RB) with similar construction standards were studied. All buildings have approximate age and are inserted into environmental aggressiveness distinct. A visual inspection took place as well as a laboratorial sample analysis of their pillars, beams and underground water reservatories. It was verified that the RB1 case, located at a high environmental aggressiveness class (III), and the RB2 case, located significatively far from the sea and classified with a moderate environmental aggressiveness class (II), both presented a medium degree of deterioration (GDE). For both buildings it is suggested a periodic inspection recommendation and a medium term intervention (GD 1 = 36,98 ; GD 2 = 31,23). The third case (RB3), located at a high environmental aggressiveness class (III) and seafront with protection barriers, presented a high degree of deterioration (GD 3=103,94). It is suggested for RB3 an immediate intervention with collapse risks

Em Março de 2004 entrou em vigor a nova versão da norma brasileira para projeto de estruturas de concreto, a NBR 6118(2003), substituindo sua antecessora que estava em vigor desde 1978. Dentre os novos conceitos apresentados, os de maior impacto no meio técnico estão relacionados à questão da durabilidade das estruturas de concreto. Assim o presente trabalho pretende avaliar a magnitude destas alterações, com ênfase à análise de custos, que ocorrem devido à aplicação dos novos conceitos normativos no Projeto estrutural de três edifícios de concreto armado de alturas variadas. Desta forma, será avaliado o impacto econômico sobre o Projeto dos edifícios, para valores de cobrimentos de concreto relativos as classes de agressividade ambiental CAA=II e CAA=III, a influência nos custos das estruturas, do valor da resistência à compressão do concreto fck, as vantagens da utilização dos modelos I e II para o cálculo das armaduras de cisalhamento de vigas. Também serão abordados o Projeto dos pilares com os novos critérios do momento mínimo de 1 ordem e imperfeições geométricas locais, a ordem de grandeza dos esforços devidos ao desaprumo frente aos esforços devidos ao vento, e finalmente o impacto no custo global das estruturas dos edifícios, quando dimensionados segundo os critérios presentes na NBR-6118(1978) e NBR-6118(2003). Os resultados mostraram que, apesar do maior volume de concreto nos projetos de acordo com a NBR 6118(2003), a quantidade de aço foi reduzida, principalmente nos pilares,em relação a NBR 6118(1978). A diferença entre os custos finais das estruturas foi a favor da NBR 6118(2003) / In March of 2004 the new version of the Brazilian Code for design of concrete structures, the NBR 6118(2003), has replaced its predecessor the NBR 6118(1978). Amongst the new presented concepts, the greatest impact is related to the question of the durability of the concrete structures. The present work evaluates the influence of the new normative criteria, with emphasis to the analysis of costs, in the structural design of three buildings of reinforced concrete of varied heights. The influence in the costs of the structures is analyzed, when designed in the different exposure classes related environmental conditions II and III, of the value adopted for the compressive resistance fck, of the use of models I and II for the calculation of the reinforcement of shear of beams, of the influence of the design of them columns with the new criteria of the minimum moment of first local order and geometric imperfections. Finally, it has been compared the global costs of the structures of the three buildings when designed according to criteria of NBR-6118(1978) and NBR- 6118(2003). The results had mainly shown that, despite the increase in concrete volume in accordance with the NBR 6118 (2003), the amount of steel was reduced, in them columns, in relation the NBR 6118(1978). The difference in final costs of the structures was favorable to the NBR 6118(1978), but it can be considered relatively low, in comparison with the increasing quality and durability proportioned by the adoption the NBR 6118(2003)

Apresenta-se neste trabalho a análise numérica de um edifício de 32 pavimentos, em concreto armado, situado na cidade do Recife. Primeiramente foi realizada a modelagem pelo método dos elementos finitos apenas para a estrutura em concreto. Em seguida realizou-se a modelagem considerando o efeito dos painéis de alvenaria de vedação no comportamento estrutural do edifício, através do modelo de barras diagonais equivalentes. E, depois, a modelagem mais refinada de alguns desses painéis, submetidos ao carregamento proveniente dos pórticos. Os resultados obtidos nos processamentos dos modelos com barras equivalentes e sem elas foram comparados entre si, a fim de se analisarem as reações de apoio e deslocamentos no topo do edifício para os dois modelos. Constatou-se um aumento na rigidez do edifício, bem como a redistribuição dos esforços. Foram analisados também os esforços nos painéis de alvenaria a fim de se verificar em que pavimentos e em que geometria de pórticos as alvenarias estavam sujeitas a maiores tensões / The work presents results from numerical analyses performed in a 32-storey reinforced concrete building in Recife. Numerical finite element analyses were performed taking into account the modeling of reinforced concrete members only as well as the masonry infill panels, considered as equivalent diagonal struts. It was also analyzed a more refined model consisting of isolated infill masonry panels subjected to frame loading from 3-D finite element analyses. Support reaction, stress resultants and displacements on the top of the buildings, obtained from performed analyses, were compared. An increase in building stiffness was observed as well as stress resultant redistribution. Infill masonry panel stresses were also investigated in order to find out the places where it is most stressed

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Nos últimos anos, a indústria da construção civil experimentou um forte crescimento na demanda por edifícios de múltiplos pavimentos de concreto armado. Este comportamento do mercado impulsionou construtores a acelerar todas as etapas do processo de construção, a fim de entregar a edificação em um tempo cada vez mais curto. Como decorrência deste fato, as estruturas são carregadas mais precocemente, ocasião em que as suas propriedades de resistência e deformação ainda não se encontram suficientemente maduras para suportar o carregamento construtivo que a solicita. Com a finalidade de compreender quais consequências são provocadas por esse carregamento prematuro da estrutura e analisar a importância dos efeitos construtivos no projeto de edificações de concreto armado, o trabalho traz o resultado de análises não-lineares realizadas com o Método dos Elementos Finitos adotando uma abordagem usualmente referida como staged construction construção em estágios aplicada a uma edificação real, situada na Cidade do Recife, Estado de Pernambuco, Brasil. Nestas análises foram levados em consideração os efeitos da retração, fluência e envelhecimento do concreto. Os resultados obtidos demonstram que os deslocamentos verticais nos pilares, decorrentes dos efeitos construtivos, são fortemente alterados quando comparados com os deslocamentos verticais resultantes da análise sem a consideração dos estágios de construção. A não consideração desses efeitos construtivos podem, em alguns casos, conduzir a manifestações patológicas importantes na edificação. / The building industry has experienced in recent years a strong growth in demand in general and in the case of reinforced concrete buildings this increase has been more marked. This fact has also contributed to accelerate all stages of the production process of these constructions with more pronounced effects on the methodologies used in the constructive steps that influence directly the structural design of the building. Structures loaded at ever earlier ages, in which the strength and deformation properties of materials are not yet sufficiently mature, it is a variable that needs to be taken into account already in the design phase so that the concrete structure behaves within acceptable level of reliability taking into account design code recommendations for service life. To understand the importance of constructive effects and to assess its magnitude in the execution of reinforced concrete buildings, this paper present result from nonlinear analyses using Finite Element Method adopting an approach commonly referred as staged construction applied to a typical building found in the practice. The effects of creep and shrinkage were considered and the results obtained demonstrate that the strains due to constructive effects can, in certain cases, assume representative values which, if ignored, can lead to important pathologies in the building.

Made available in DSpace on 2017-06-01T17:57:20Z (GMT). No. of bitstreams: 1 Elilde Medeiros.pdf: 1143833 bytes, checksum: 753821a53256142f318470c59cb69f82 (MD5) Previous issue date: 2007-08-17 / The work presents results from numerical analyses performed in a 32-storey reinforced concrete building in Recife. Numerical finite element analyses were performed taking into account the modeling of reinforced concrete members only as well as the masonry infill panels, considered as equivalent diagonal struts. It was also analyzed a more refined model consisting of isolated infill masonry panels subjected to frame loading from 3-D finite element analyses. Support reaction, stress resultants and displacements on the top of the buildings, obtained from performed analyses, were compared. An increase in building stiffness was observed as well as stress resultant redistribution. Infill masonry panel stresses were also investigated in order to find out the places where it is most stressed / Apresenta-se neste trabalho a análise numérica de um edifício de 32 pavimentos, em concreto armado, situado na cidade do Recife. Primeiramente foi realizada a modelagem pelo método dos elementos finitos apenas para a estrutura em concreto. Em seguida realizou-se a modelagem considerando o efeito dos painéis de alvenaria de vedação no comportamento estrutural do edifício, através do modelo de barras diagonais equivalentes. E, depois, a modelagem mais refinada de alguns desses painéis, submetidos ao carregamento proveniente dos pórticos. Os resultados obtidos nos processamentos dos modelos com barras equivalentes e sem elas foram comparados entre si, a fim de se analisarem as reações de apoio e deslocamentos no topo do edifício para os dois modelos. Constatou-se um aumento na rigidez do edifício, bem como a redistribuição dos esforços. Foram analisados também os esforços nos painéis de alvenaria a fim de se verificar em que pavimentos e em que geometria de pórticos as alvenarias estavam sujeitas a maiores tensões

Made available in DSpace on 2017-06-01T17:57:22Z (GMT). No. of bitstreams: 1 Fuad Zarzar_dissert.pdf: 2776007 bytes, checksum: aabaf5bf493a96131a98e3b91918ee12 (MD5) Previous issue date: 2007-08-16 / This Work, based on parts of the ISO 15686, presents and discuss about a deterministic method, Factor Method (FM), that permits to predict material service life and their components and planning their maintenance and replacement necessary periodicity. The precision of the estimates of this method was analyzed in this Work, and an alternative equation to evaluate service life was developed, using multiple linear regression (MLR), derived from FM pertaining to ISO 15686-1 and especially the Factor Method. The MLR is broadly used to evaluate products that interact with independents variables. Finally, this alternative equation was used to compare its estimate random results with the FM random ones. After evaluating the examples on chapter 4, the Author noticed that the Factor Method is very important to estimate service life of materials and components and the alternative equation too. Two case studies were done in this Work, in the first case the total service life of three collapsed structures were estimated. First a concrete structure similar to a building that was located in the Metropolitan Area of Recife (Brazil) and then the total service life of an balcony from a building located at the city of Rio de Janeiro (Brazil) using both the Factor Method and the alternative equation, and finally the total service life of the basement and superstructure of specific buildings called box from the Metropolitan Region of Recife using the Delphi Method together with the Factor Method was realized too. In the second case, the service life estimation of a softwood window was done using the FM and the alternative equation, other estimations of service life were done the same way by using the alternative equation and the FM. Despite the equations presented in this Work have been developed specifically to estimate service life of materials and components, the estimates showed that the precision of the total service life of the first case approximated to the real case studies, proving the potentiality of the methods / Este Trabalho, baseado nas determinações da norma ISO 15686, apresenta e discute um método determinístico, o Método dos Fatores (MF), que permite estimar a vida útil de materiais e componentes e planejar a periodicidade necessária de manutenção e substituição dos referidos materiais e componentes. A precisão das estimativas desse método foi analisada, neste Trabalho. Uma Equação Alternativa para estimar a vida útil, também, foi desenvolvida, usando regressão linear múltipla (RLM), derivada do MF pertencente a ISO 15686-1. A RLM é, largamente, usada para avaliar ou estimar produtos que interajam com variáveis independentes. Finalmente, a supra mencionada Equação Alternativa foi utilizada para comparar os resultados aleatórios de suas estimativas com os resultados aleatórios das estimativas do MF. Analisando os exemplos do Capítulo 4, constatou-se que o Método dos Fatores é muito importante para estimar a vida útil de materiais e componentes, e a Equação Alternativa, também. Foram efetuados dois estudos de casos diferentes. No primeiro caso as vidas úteis totais de três estruturas de concreto que colapsaram foram estimadas. Primeiro a vida útil total de um edifício similar ao que colapsou na Região Metropolitana do Recife (PE), depois a vida útil total da varanda de um prédio, construído na Cidade do Rio de Janeiro (RJ) usando o MF e a Equação Alternativa. Finalmente, foi feita, também a estimativa da vida útil total do embasamento e superestrutura de prédios do tipo caixão (exemplo nº4), que colapsaram na Região Metropolitana do Recife, usando o Método Delphi em conjunto com o Método dos Fatores. No segundo caso, foram feitas as estimativas das vidas úteis de uma janela de madeira mole, usando ambos o MF e a Equação Alternativa. As demais estimativas de vida útil das outras estruturas de concreto foram conseguidas da mesma forma. As estimativas de vida útil total do primeiro caso se aproximaram dos casos reais estudados, apesar de as equações apresentadas neste Trabalho terem sido desenvolvidas, exclusivamente, para estimar a vida útil de materiais e componentes, provando, assim, a potencialidade das estimativas.